Royce  Reinger

Royce Reinger

1659707040

Phobos: Simplifying Kafka for Ruby Apps

Phobos

Simplifying Kafka for Ruby apps!

Phobos is a micro framework and library for applications dealing with Apache Kafka.

  • It wraps common behaviors needed by consumers and producers in an easy and convenient API
  • It uses ruby-kafka as its Kafka client and core component
  • It provides a CLI for starting and stopping a standalone application ready to be used for production purposes

Why Phobos? Why not ruby-kafka directly? Well, ruby-kafka is just a client. You still need to write a lot of code to manage proper consuming and producing of messages. You need to do proper message routing, error handling, retrying, backing off and maybe logging/instrumenting the message management process. You also need to worry about setting up a platform independent test environment that works on CI as well as any local machine, and even on your deployment pipeline. Finally, you also need to consider how to deploy your app and how to start it.

With Phobos by your side, all this becomes smooth sailing.

Installation

Add this line to your application's Gemfile:

gem 'phobos'

And then execute:

$ bundle

Or install it yourself as:

$ gem install phobos

Usage

Phobos can be used in two ways: as a standalone application or to support Kafka features in your existing project - including Rails apps. It provides a CLI tool to run it.

Standalone apps

Standalone apps have benefits such as individual deploys and smaller code bases. If consuming from Kafka is your version of microservices, Phobos can be of great help.

Setup

To create an application with Phobos you need two things:

  • A configuration file (more details in the Configuration file section)
  • A phobos_boot.rb (or the name of your choice) to properly load your code into Phobos executor

Use the Phobos CLI command init to bootstrap your application. Example:

# call this command inside your app folder
$ phobos init
    create  config/phobos.yml
    create  phobos_boot.rb

phobos.yml is the configuration file and phobos_boot.rb is the place to load your code.

Consumers (listeners and handlers)

In Phobos apps listeners are configured against Kafka - they are our consumers. A listener requires a handler (a ruby class where you should process incoming messages), a Kafka topic, and a Kafka group_id. Consumer groups are used to coordinate the listeners across machines. We write the handlers and Phobos makes sure to run them for us. An example of a handler is:

class MyHandler
  include Phobos::Handler

  def consume(payload, metadata)
    # payload  - This is the content of your Kafka message, Phobos does not attempt to
    #            parse this content, it is delivered raw to you
    # metadata - A hash with useful information about this event, it contains: The event key,
    #            partition number, offset, retry_count, topic, group_id, and listener_id
  end
end

Writing a handler is all you need to allow Phobos to work - it will take care of execution, retries and concurrency.

To start Phobos the start command is used, example:

$ phobos start
[2016-08-13T17:29:59:218+0200Z] INFO  -- Phobos : <Hash> {:message=>"Phobos configured", :env=>"development"}
______ _           _
| ___ \ |         | |
| |_/ / |__   ___ | |__   ___  ___
|  __/| '_ \ / _ \| '_ \ / _ \/ __|
| |   | | | | (_) | |_) | (_) \__ \
\_|   |_| |_|\___/|_.__/ \___/|___/

phobos_boot.rb - find this file at ~/Projects/example/phobos_boot.rb

[2016-08-13T17:29:59:272+0200Z] INFO  -- Phobos : <Hash> {:message=>"Listener started", :listener_id=>"6d5d2c", :group_id=>"test-1", :topic=>"test"}

By default, the start command will look for the configuration file at config/phobos.yml and it will load the file phobos_boot.rb if it exists. In the example above all example files generated by the init command are used as is. It is possible to change both files, use -c for the configuration file and -b for the boot file. Example:

$ phobos start -c /var/configs/my.yml -b /opt/apps/boot.rb

You may also choose to configure phobos with a hash from within your boot file. In this case, disable loading the config file with the --skip-config option:

$ phobos start -b /opt/apps/boot.rb --skip-config

Consuming messages from Kafka

Messages from Kafka are consumed using handlers. You can use Phobos executors or include it in your own project as a library, but handlers will always be used. To create a handler class, simply include the module Phobos::Handler. This module allows Phobos to manage the life cycle of your handler.

A handler is required to implement the method #consume(payload, metadata).

Instances of your handler will be created for every message, so keep a constructor without arguments. If consume raises an exception, Phobos will retry the message indefinitely, applying the back off configuration presented in the configuration file. The metadata hash will contain a key called retry_count with the current number of retries for this message. To skip a message, simply return from #consume.

The metadata hash will also contain a key called headers with the headers of the consumed message.

When the listener starts, the class method .start will be called with the kafka_client used by the listener. Use this hook as a chance to setup necessary code for your handler. The class method .stop will be called during listener shutdown.

class MyHandler
  include Phobos::Handler

  def self.start(kafka_client)
    # setup handler
  end

  def self.stop
    # teardown
  end

  def consume(payload, metadata)
    # consume or skip message
  end
end

It is also possible to control the execution of #consume with the method #around_consume(payload, metadata). This method receives the payload and metadata, and then invokes #consume method by means of a block; example:

class MyHandler
  include Phobos::Handler

  def around_consume(payload, metadata)
    Phobos.logger.info "consuming..."
    output = yield payload, metadata
    Phobos.logger.info "done, output: #{output}"
  end

  def consume(payload, metadata)
    # consume or skip message
  end
end

Note: around_consume was previously defined as a class method. The current code supports both implementations, giving precendence to the class method, but future versions will no longer support .around_consume.

class MyHandler
  include Phobos::Handler

  def self.around_consume(payload, metadata)
    Phobos.logger.info "consuming..."
    output = yield payload, metadata
    Phobos.logger.info "done, output: #{output}"
  end

  def consume(payload, metadata)
    # consume or skip message
  end
end

Take a look at the examples folder for some ideas.

The hander life cycle can be illustrated as:

.start -> #consume -> .stop

or optionally,

.start -> #around_consume [ #consume ] -> .stop

Batch Consumption

In addition to the regular handler, Phobos provides a BatchHandler. The basic ideas are identical, except that instead of being passed a single message at a time, the BatchHandler is passed a batch of messages. All methods follow the same pattern as the regular handler except that they each end in _batch and are passed an array of Phobos::BatchMessages instead of a single payload.

To enable handling of batches on the consumer side, you must specify a delivery method of inline_batch in phobos.yml, and your handler must include BatchHandler. Using a delivery method of batch assumes that you are still processing the messages one at a time and should use Handler.

When using inline_batch, each instance of Phobos::BatchMessage will contain an instance method headers with the headers for that message.

class MyBatchHandler
  include Phobos::BatchHandler

  def around_consume_batch(payloads, metadata)
    payloads.each do |p|
      p.payload[:timestamp] = Time.zone.now
    end

    yield payloads, metadata
  end

  def consume_batch(payloads, metadata)
    payloads.each do |p|
      logger.info("Got payload #{p.payload}, #{p.partition}, #{p.offset}, #{p.key}, #{p.payload[:timestamp]}")
    end
  end

end

Note that retry logic will happen on the batch level in this case. If you are processing messages individually and an error happens in the middle, Phobos's retry logic will retry the entire batch. If this is not the behavior you want, consider using batch instead of inline_batch.

Producing messages to Kafka

ruby-kafka provides several options for publishing messages, Phobos offers them through the module Phobos::Producer. It is possible to turn any ruby class into a producer (including your handlers), just include the producer module, example:

class MyProducer
  include Phobos::Producer
end

Phobos is designed for multi threading, thus the producer is always bound to the current thread. It is possible to publish messages from objects and classes, pick the option that suits your code better. The producer module doesn't pollute your classes with a thousand methods, it includes a single method the class and in the instance level: producer.

my = MyProducer.new
my.producer.publish(topic: 'topic', payload: 'message-payload', key: 'partition and message key')

# The code above has the same effect of this code:
MyProducer.producer.publish(topic: 'topic', payload: 'message-payload', key: 'partition and message key')

The signature for the publish method is as follows:

def publish(topic: topic, payload: payload, key: nil, partition_key: nil, headers: nil)

When publishing a message with headers, the headers argument must be a hash:

my = MyProducer.new
my.producer.publish(topic: 'topic', payload: 'message-payload', key: 'partition and message key', headers: { header_1: 'value 1' })

It is also possible to publish several messages at once:

MyProducer
  .producer
  .publish_list([
    { topic: 'A', payload: 'message-1', key: '1' },
    { topic: 'B', payload: 'message-2', key: '2' },
    { topic: 'B', payload: 'message-3', key: '3', headers: { header_1: 'value 1', header_2: 'value 2' } }
  ])

There are two flavors of producers: regular producers and async producers.

Regular producers will deliver the messages synchronously and disconnect, it doesn't matter if you use publish or publish_list; by default, after the messages get delivered the producer will disconnect.

Async producers will accept your messages without blocking, use the methods async_publish and async_publish_list to use async producers.

An example of using handlers to publish messages:

class MyHandler
  include Phobos::Handler
  include Phobos::Producer

  PUBLISH_TO = 'topic2'

  def consume(payload, metadata)
    producer.async_publish(topic: PUBLISH_TO, payload: {key: 'value'}.to_json)
  end
end

Note about configuring producers

Since the handler life cycle is managed by the Listener, it will make sure the producer is properly closed before it stops. When calling the producer outside a handler remember, you need to shutdown them manually before you close the application. Use the class method async_producer_shutdown to safely shutdown the producer.

Without configuring the Kafka client, the producers will create a new one when needed (once per thread). To disconnect from kafka call kafka_client.close.

# This method will block until everything is safely closed
MyProducer
  .producer
  .async_producer_shutdown

MyProducer
  .producer
  .kafka_client
  .close

Note about producers with persistent connections

By default, regular producers will automatically disconnect after every publish call. You can change this behavior (which reduces connection overhead, TLS etc - which increases speed significantly) by setting the persistent_connections config in phobos.yml. When set, regular producers behave identically to async producers and will also need to be shutdown manually using the sync_producer_shutdown method.

Since regular producers with persistent connections have open connections, you need to manually disconnect from Kafka when ending your producers' life cycle:

MyProducer
  .producer
  .sync_producer_shutdown

Phobos as a library in an existing project

When running as a standalone service, Phobos sets up a Listener and Executor for you. When you use Phobos as a library in your own project, you need to set these components up yourself.

First, call the method configure with the path of your configuration file or with configuration settings hash.

Phobos.configure('config/phobos.yml')

or

Phobos.configure(kafka: { client_id: 'phobos' }, logger: { file: 'log/phobos.log' })

Listener connects to Kafka and acts as your consumer. To create a listener you need a handler class, a topic, and a group id.

listener = Phobos::Listener.new(
  handler: Phobos::EchoHandler,
  group_id: 'group1',
  topic: 'test'
)

# start method blocks
Thread.new { listener.start }

listener.id # 6d5d2c (all listeners have an id)
listener.stop # stop doesn't block

This is all you need to consume from Kafka with back off retries.

An executor is the supervisor of all listeners. It loads all listeners configured in phobos.yml. The executor keeps the listeners running and restarts them when needed.

executor = Phobos::Executor.new

# start doesn't block
executor.start

# stop will block until all listers are properly stopped
executor.stop

When using Phobos executors you don't care about how listeners are created, just provide the configuration under the listeners section in the configuration file and you are good to go.

Configuration file

The configuration file is organized in 6 sections. Take a look at the example file, config/phobos.yml.example.

The file will be parsed through ERB so ERB syntax/file extension is supported beside the YML format.

logger configures the logger for all Phobos components. It automatically outputs to STDOUT and it saves the log in the configured file.

kafka provides configurations for every Kafka::Client created over the application. All options supported by ruby-kafka can be provided.

producer provides configurations for all producers created over the application, the options are the same for regular and async producers. All options supported by ruby-kafka can be provided. If the kafka key is present under producer, it is merged into the top-level kafka, allowing different connection configuration for producers.

consumer provides configurations for all consumer groups created over the application. All options supported by ruby-kafka can be provided. If the kafka key is present under consumer, it is merged into the top-level kafka, allowing different connection configuration for consumers.

backoff Phobos provides automatic retries for your handlers. If an exception is raised, the listener will retry following the back off configured here. Backoff can also be configured per listener.

listeners is the list of listeners configured. Each listener represents a consumer group.

Additional listener configuration

In some cases it's useful to share most of the configuration between multiple phobos processes, but have each process run different listeners. In that case, a separate yaml file can be created and loaded with the -l flag. Example:

$ phobos start -c /var/configs/my.yml -l /var/configs/additional_listeners.yml

Note that the config file must still specify a listeners section, though it can be empty.

Custom configuration/logging

Phobos can be configured using a hash rather than the config file directly. This can be useful if you want to do some pre-processing before sending the file to Phobos. One particularly useful aspect is the ability to provide Phobos with a custom logger, e.g. by reusing the Rails logger:

Phobos.configure(
  custom_logger: Rails.logger,
  custom_kafka_logger: Rails.logger
)

If these keys are given, they will override the logger keys in the Phobos config file.

Instrumentation

Some operations are instrumented using Active Support Notifications.

In order to receive notifications you can use the module Phobos::Instrumentation, example:

Phobos::Instrumentation.subscribe('listener.start') do |event|
  puts(event.payload)
end

Phobos::Instrumentation is a convenience module around ActiveSupport::Notifications, feel free to use it or not. All Phobos events are in the phobos namespace. Phobos::Instrumentation will always look at phobos. events.

Executor notifications

  • executor.retry_listener_error is sent when the listener crashes and the executor wait for a restart. It includes the following payload:
    • listener_id
    • retry_count
    • waiting_time
    • exception_class
    • exception_message
    • backtrace
  • executor.stop is sent when executor stops

Listener notifications

  • listener.start_handler is sent when invoking handler.start(kafka_client). It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
  • listener.start is sent when listener starts. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
  • listener.process_batch is sent after process a batch. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
    • batch_size
    • partition
    • offset_lag
    • highwater_mark_offset
  • listener.process_message is sent after processing a message. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
    • key
    • partition
    • offset
    • retry_count
  • listener.process_batch_inline is sent after processing a batch with batch_inline mode. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
    • batch_size
    • partition
    • offset_lag
    • retry_count
  • listener.retry_handler_error is sent after waiting for handler#consume retry. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
    • key
    • partition
    • offset
    • retry_count
    • waiting_time
    • exception_class
    • exception_message
    • backtrace
  • listener.retry_handler_error_batch is sent after waiting for handler#consume_batch retry. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
    • batch_size
    • partition
    • offset_lag
    • retry_count
    • waiting_time
    • exception_class
    • exception_message
    • backtrace
  • listener.retry_aborted is sent after waiting for a retry but the listener was stopped before the retry happened. It includes the following payload:
    • listener_id
    • group_id
    • topic
    • handler
  • listener.stopping is sent when the listener receives signal to stop.
    • listener_id
    • group_id
    • topic
    • handler
  • listener.stop_handler is sent after stopping the handler.
    • listener_id
    • group_id
    • topic
    • handler
  • listener.stop is send after stopping the listener.
    • listener_id
    • group_id
    • topic
    • handler

Plugins

List of gems that enhance Phobos:

Phobos DB Checkpoint is drop in replacement to Phobos::Handler, extending it with the following features:

  • Persists your Kafka events to an active record compatible database
  • Ensures that your handler will consume messages only once
  • Allows your system to quickly reprocess events in case of failures

Phobos Checkpoint UI gives your Phobos DB Checkpoint powered app a web gui with the features below. Maintaining a Kafka consumer app has never been smoother:

  • Search events and inspect payload
  • See failures and retry / delete them

Phobos Prometheus adds prometheus metrics to your phobos consumer.

  • Measures total messages and batches processed
  • Measures total duration needed to process each message (and batch)
  • Adds /metrics endpoit to scrape data

Development

After checking out the repo:

  • make sure docker is installed and running (for windows and mac this also includes docker-compose).
  • Linux: make sure docker-compose is installed and running.
  • run bin/setup to install dependencies
  • run docker-compose up -d --force-recreate kafka zookeeper to start the required kafka containers
  • run tests to confirm no environmental issues
    • wait a few seconds for kafka broker to get set up - sleep 30
    • run docker-compose run --rm test
    • make sure it reports X examples, 0 failures

You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Test

Phobos exports a spec helper that can help you test your consumer. The Phobos lifecycle will conveniently be activated for you with minimal setup required.

  • process_message(handler:, payload:, metadata: {}, encoding: nil) - Invokes your handler with payload and metadata, using a dummy listener (encoding and metadata are optional).
### spec_helper.rb
require 'phobos/test/helper'
RSpec.configure do |config|
  config.include Phobos::Test::Helper
  config.before(:each) do
    Phobos.configure(path_to_my_config_file)
  end
end 

### Spec file
describe MyConsumer do
  let(:payload) { 'foo' }
  let(:metadata) { Hash(foo: 'bar') }

  it 'consumes my message' do
    expect_any_instance_of(described_class).to receive(:around_consume).with(payload, metadata).once.and_call_original
    expect_any_instance_of(described_class).to receive(:consume).with(payload, metadata).once.and_call_original

    process_message(handler: described_class, payload: payload, metadata: metadata)
  end
end

Upgrade Notes

Version 2.0 removes deprecated ways of defining producers and consumers:

  • The before_consume method has been removed. You can have this behavior in the first part of an around_consume method.
  • around_consume is now only available as an instance method, and it must yield the values to pass to the consume method.
  • publish and async_publish now only accept keyword arguments, not positional arguments.

Example pre-2.0:

class MyHandler
  include Phobos::Handler

  def before_consume(payload, metadata)
    payload[:id] = 1
  end

  def self.around_consume(payload, metadata)
    metadata[:key] = 5
    yield
  end
end

In 2.0:

class MyHandler
  include Phobos::Handler

  def around_consume(payload, metadata)
    new_payload = payload.dup
    new_metadata = metadata.dup
    new_payload[:id] = 1
    new_metadata[:key] = 5
    yield new_payload, new_metadata
  end
end

Producer, 1.9:

  producer.publish('my-topic', { payload_value: 1}, 5, 3, {header_val: 5})

Producer 2.0:

  producer.publish(topic: 'my-topic', payload: { payload_value: 1}, key: 5, 
     partition_key: 3, headers: { header_val: 5})

Version 1.8.2 introduced a new persistent_connections setting for regular producers. This reduces the number of connections used to produce messages and you should consider setting it to true. This does require a manual shutdown call - please see Producers with persistent connections.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/klarna/phobos.

Linting

Phobos projects Rubocop to lint the code, and in addition all projects use Rubocop Rules to maintain a shared rubocop configuration. Updates to the shared configurations are done in phobos/shared repo, where you can also find instructions on how to apply the new settings to the Phobos projects.

Acknowledgements

Thanks to Sebastian Norde for the awesome logo!

Author: Phobos
Source Code: https://github.com/phobos/phobos 
License: Apache-2.0 license

#ruby #kafka 

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Phobos: Simplifying Kafka for Ruby Apps
Carmen  Grimes

Carmen Grimes

1595491178

Best Electric Bikes and Scooters for Rental Business or Campus Facility

The electric scooter revolution has caught on super-fast taking many cities across the globe by storm. eScooters, a renovated version of old-school scooters now turned into electric vehicles are an environmentally friendly solution to current on-demand commute problems. They work on engines, like cars, enabling short traveling distances without hassle. The result is that these groundbreaking electric machines can now provide faster transport for less — cheaper than Uber and faster than Metro.

Since they are durable, fast, easy to operate and maintain, and are more convenient to park compared to four-wheelers, the eScooters trend has and continues to spike interest as a promising growth area. Several companies and universities are increasingly setting up shop to provide eScooter services realizing a would-be profitable business model and a ready customer base that is university students or residents in need of faster and cheap travel going about their business in school, town, and other surrounding areas.

Electric Scooters Trends and Statistics

In many countries including the U.S., Canada, Mexico, U.K., Germany, France, China, Japan, India, Brazil and Mexico and more, a growing number of eScooter users both locals and tourists can now be seen effortlessly passing lines of drivers stuck in the endless and unmoving traffic.

A recent report by McKinsey revealed that the E-Scooter industry will be worth― $200 billion to $300 billion in the United States, $100 billion to $150 billion in Europe, and $30 billion to $50 billion in China in 2030. The e-Scooter revenue model will also spike and is projected to rise by more than 20% amounting to approximately $5 billion.

And, with a necessity to move people away from high carbon prints, traffic and congestion issues brought about by car-centric transport systems in cities, more and more city planners are developing more bike/scooter lanes and adopting zero-emission plans. This is the force behind the booming electric scooter market and the numbers will only go higher and higher.

Companies that have taken advantage of the growing eScooter trend develop an appthat allows them to provide efficient eScooter services. Such an app enables them to be able to locate bike pick-up and drop points through fully integrated google maps.

List of Best Electric Bikes for Rental Business or Campus Facility 2020:

It’s clear that e scooters will increasingly become more common and the e-scooter business model will continue to grab the attention of manufacturers, investors, entrepreneurs. All this should go ahead with a quest to know what are some of the best electric bikes in the market especially for anyone who would want to get started in the electric bikes/scooters rental business.

We have done a comprehensive list of the best electric bikes! Each bike has been reviewed in depth and includes a full list of specs and a photo.

Billy eBike

mobile-best-electric-bikes-scooters https://www.kickstarter.com/projects/enkicycles/billy-were-redefining-joyrides

To start us off is the Billy eBike, a powerful go-anywhere urban electric bike that’s specially designed to offer an exciting ride like no other whether you want to ride to the grocery store, cafe, work or school. The Billy eBike comes in 4 color options – Billy Blue, Polished aluminium, Artic white, and Stealth black.

Price: $2490

Available countries

Available in the USA, Europe, Asia, South Africa and Australia.This item ships from the USA. Buyers are therefore responsible for any taxes and/or customs duties incurred once it arrives in your country.

Features

  • Control – Ride with confidence with our ultra-wide BMX bars and a hyper-responsive twist throttle.
  • Stealth- Ride like a ninja with our Gates carbon drive that’s as smooth as butter and maintenance-free.
  • Drive – Ride further with our high torque fat bike motor, giving a better climbing performance.
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  • Customize – Ride your own way with 5 levels of power control. Each level determines power and speed.
  • Flickable – Ride harder with our BMX /MotoX inspired geometry and lightweight aluminum package

Specifications

  • Maximum speed: 20 mph (32 km/h)
  • Range per charge: 41 miles (66 km)
  • Maximum Power: 500W
  • Motor type: Fat Bike Motor: Bafang RM G060.500.DC
  • Load capacity: 300lbs (136kg)
  • Battery type: 13.6Ah Samsung lithium-ion,
  • Battery capacity: On/off-bike charging available
  • Weight: w/o batt. 48.5lbs (22kg), w/ batt. 54lbs (24.5kg)
  • Front Suspension: Fully adjustable air shock, preload/compression damping /lockout
  • Rear Suspension: spring, preload adjustment
  • Built-in GPS

Why Should You Buy This?

  • Riding fun and excitement
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  • Ride with confidence
  • Billy folds for convenient storage and transportation.
  • Shorty levers connect to disc brakes ensuring you stop on a dime
  • belt drives are maintenance-free and clean (no oil or lubrication needed)

**Who Should Ride Billy? **

Both new and experienced riders

**Where to Buy? **Local distributors or ships from the USA.

Genze 200 series e-Bike

genze-best-electric-bikes-scooters https://www.genze.com/fleet/

Featuring a sleek and lightweight aluminum frame design, the 200-Series ebike takes your riding experience to greater heights. Available in both black and white this ebike comes with a connected app, which allows you to plan activities, map distances and routes while also allowing connections with fellow riders.

Price: $2099.00

Available countries

The Genze 200 series e-Bike is available at GenZe retail locations across the U.S or online via GenZe.com website. Customers from outside the US can ship the product while incurring the relevant charges.

Features

  • 2 Frame Options
  • 2 Sizes
  • Integrated/Removable Battery
  • Throttle and Pedal Assist Ride Modes
  • Integrated LCD Display
  • Connected App
  • 24 month warranty
  • GPS navigation
  • Bluetooth connectivity

Specifications

  • Maximum speed: 20 mph with throttle
  • Range per charge: 15-18 miles w/ throttle and 30-50 miles w/ pedal assist
  • Charging time: 3.5 hours
  • Motor type: Brushless Rear Hub Motor
  • Gears: Microshift Thumb Shifter
  • Battery type: Removable Samsung 36V, 9.6AH Li-Ion battery pack
  • Battery capacity: 36V and 350 Wh
  • Weight: 46 pounds
  • Derailleur: 8-speed Shimano
  • Brakes: Dual classic
  • Wheels: 26 x 20 inches
  • Frame: 16, and 18 inches
  • Operating Mode: Analog mode 5 levels of Pedal Assist Thrott­le Mode

Norco from eBikestore

norco-best-electric-bikes-scooters https://ebikestore.com/shop/norco-vlt-s2/

The Norco VLT S2 is a front suspension e-Bike with solid components alongside the reliable Bosch Performance Line Power systems that offer precise pedal assistance during any riding situation.

Price: $2,699.00

Available countries

This item is available via the various Norco bikes international distributors.

Features

  • VLT aluminum frame- for stiffness and wheel security.
  • Bosch e-bike system – for their reliability and performance.
  • E-bike components – for added durability.
  • Hydraulic disc brakes – offer riders more stopping power for safety and control at higher speeds.
  • Practical design features – to add convenience and versatility.

Specifications

  • Maximum speed: KMC X9 9spd
  • Motor type: Bosch Active Line
  • Gears: Shimano Altus RD-M2000, SGS, 9 Speed
  • Battery type: Power Pack 400
  • Battery capacity: 396Wh
  • Suspension: SR Suntour suspension fork
  • Frame: Norco VLT, Aluminum, 12x142mm TA Dropouts

Bodo EV

bodo-best-electric-bikes-scootershttp://www.bodoevs.com/bodoev/products_show.asp?product_id=13

Manufactured by Bodo Vehicle Group Limited, the Bodo EV is specially designed for strong power and extraordinary long service to facilitate super amazing rides. The Bodo Vehicle Company is a striking top in electric vehicles brand field in China and across the globe. Their Bodo EV will no doubt provide your riders with high-level riding satisfaction owing to its high-quality design, strength, breaking stability and speed.

Price: $799

Available countries

This item ships from China with buyers bearing the shipping costs and other variables prior to delivery.

Features

  • Reliable
  • Environment friendly
  • Comfortable riding
  • Fashionable
  • Economical
  • Durable – long service life
  • Braking stability
  • LED lighting technology

Specifications

  • Maximum speed: 45km/h
  • Range per charge: 50km per person
  • Charging time: 8 hours
  • Maximum Power: 3000W
  • Motor type: Brushless DC Motor
  • Load capacity: 100kg
  • Battery type: Lead-acid battery
  • Battery capacity: 60V 20AH
  • Weight: w/o battery 47kg

#android app #autorent #entrepreneurship #ios app #minimum viable product (mvp) #mobile app development #news #app like bird #app like bounce #app like lime #autorent #best electric bikes 2020 #best electric bikes for rental business #best electric kick scooters 2020 #best electric kickscooters for rental business #best electric scooters 2020 #best electric scooters for rental business #bird scooter business model #bird scooter rental #bird scooter rental cost #bird scooter rental price #clone app like bird #clone app like bounce #clone app like lime #electric rental scooters #electric scooter company #electric scooter rental business #how do you start a moped #how to start a moped #how to start a scooter rental business #how to start an electric company #how to start electric scooterrental business #lime scooter business model #scooter franchise #scooter rental business #scooter rental business for sale #scooter rental business insurance #scooters franchise cost #white label app like bird #white label app like bounce #white label app like lime

Carmen  Grimes

Carmen Grimes

1595494844

How to start an electric scooter facility/fleet in a university campus/IT park

Are you leading an organization that has a large campus, e.g., a large university? You are probably thinking of introducing an electric scooter/bicycle fleet on the campus, and why wouldn’t you?

Introducing micro-mobility in your campus with the help of such a fleet would help the people on the campus significantly. People would save money since they don’t need to use a car for a short distance. Your campus will see a drastic reduction in congestion, moreover, its carbon footprint will reduce.

Micro-mobility is relatively new though and you would need help. You would need to select an appropriate fleet of vehicles. The people on your campus would need to find electric scooters or electric bikes for commuting, and you need to provide a solution for this.

To be more specific, you need a short-term electric bike rental app. With such an app, you will be able to easily offer micro-mobility to the people on the campus. We at Devathon have built Autorent exactly for this.

What does Autorent do and how can it help you? How does it enable you to introduce micro-mobility on your campus? We explain these in this article, however, we will touch upon a few basics first.

Micro-mobility: What it is

micro-mobility

You are probably thinking about micro-mobility relatively recently, aren’t you? A few relevant insights about it could help you to better appreciate its importance.

Micro-mobility is a new trend in transportation, and it uses vehicles that are considerably smaller than cars. Electric scooters (e-scooters) and electric bikes (e-bikes) are the most popular forms of micro-mobility, however, there are also e-unicycles and e-skateboards.

You might have already seen e-scooters, which are kick scooters that come with a motor. Thanks to its motor, an e-scooter can achieve a speed of up to 20 km/h. On the other hand, e-bikes are popular in China and Japan, and they come with a motor, and you can reach a speed of 40 km/h.

You obviously can’t use these vehicles for very long commutes, however, what if you need to travel a short distance? Even if you have a reasonable public transport facility in the city, it might not cover the route you need to take. Take the example of a large university campus. Such a campus is often at a considerable distance from the central business district of the city where it’s located. While public transport facilities may serve the central business district, they wouldn’t serve this large campus. Currently, many people drive their cars even for short distances.

As you know, that brings its own set of challenges. Vehicular traffic adds significantly to pollution, moreover, finding a parking spot can be hard in crowded urban districts.

Well, you can reduce your carbon footprint if you use an electric car. However, electric cars are still new, and many countries are still building the necessary infrastructure for them. Your large campus might not have the necessary infrastructure for them either. Presently, electric cars don’t represent a viable option in most geographies.

As a result, you need to buy and maintain a car even if your commute is short. In addition to dealing with parking problems, you need to spend significantly on your car.

All of these factors have combined to make people sit up and think seriously about cars. Many people are now seriously considering whether a car is really the best option even if they have to commute only a short distance.

This is where micro-mobility enters the picture. When you commute a short distance regularly, e-scooters or e-bikes are viable options. You limit your carbon footprints and you cut costs!

Businesses have seen this shift in thinking, and e-scooter companies like Lime and Bird have entered this field in a big way. They let you rent e-scooters by the minute. On the other hand, start-ups like Jump and Lyft have entered the e-bike market.

Think of your campus now! The people there might need to travel short distances within the campus, and e-scooters can really help them.

How micro-mobility can benefit you

benefits-micromobility

What advantages can you get from micro-mobility? Let’s take a deeper look into this question.

Micro-mobility can offer several advantages to the people on your campus, e.g.:

  • Affordability: Shared e-scooters are cheaper than other mass transportation options. Remember that the people on your campus will use them on a shared basis, and they will pay for their short commutes only. Well, depending on your operating model, you might even let them use shared e-scooters or e-bikes for free!
  • Convenience: Users don’t need to worry about finding parking spots for shared e-scooters since these are small. They can easily travel from point A to point B on your campus with the help of these e-scooters.
  • Environmentally sustainable: Shared e-scooters reduce the carbon footprint, moreover, they decongest the roads. Statistics from the pilot programs in cities like Portland and Denver showimpressive gains around this key aspect.
  • Safety: This one’s obvious, isn’t it? When people on your campus use small e-scooters or e-bikes instead of cars, the problem of overspeeding will disappear. you will see fewer accidents.

#android app #autorent #ios app #mobile app development #app like bird #app like bounce #app like lime #autorent #bird scooter business model #bird scooter rental #bird scooter rental cost #bird scooter rental price #clone app like bird #clone app like bounce #clone app like lime #electric rental scooters #electric scooter company #electric scooter rental business #how do you start a moped #how to start a moped #how to start a scooter rental business #how to start an electric company #how to start electric scooterrental business #lime scooter business model #scooter franchise #scooter rental business #scooter rental business for sale #scooter rental business insurance #scooters franchise cost #white label app like bird #white label app like bounce #white label app like lime

Fredy  Larson

Fredy Larson

1595059664

How long does it take to develop/build an app?

With more of us using smartphones, the popularity of mobile applications has exploded. In the digital era, the number of people looking for products and services online is growing rapidly. Smartphone owners look for mobile applications that give them quick access to companies’ products and services. As a result, mobile apps provide customers with a lot of benefits in just one device.

Likewise, companies use mobile apps to increase customer loyalty and improve their services. Mobile Developers are in high demand as companies use apps not only to create brand awareness but also to gather information. For that reason, mobile apps are used as tools to collect valuable data from customers to help companies improve their offer.

There are many types of mobile applications, each with its own advantages. For example, native apps perform better, while web apps don’t need to be customized for the platform or operating system (OS). Likewise, hybrid apps provide users with comfortable user experience. However, you may be wondering how long it takes to develop an app.

To give you an idea of how long the app development process takes, here’s a short guide.

App Idea & Research

app-idea-research

_Average time spent: two to five weeks _

This is the initial stage and a crucial step in setting the project in the right direction. In this stage, you brainstorm ideas and select the best one. Apart from that, you’ll need to do some research to see if your idea is viable. Remember that coming up with an idea is easy; the hard part is to make it a reality.

All your ideas may seem viable, but you still have to run some tests to keep it as real as possible. For that reason, when Web Developers are building a web app, they analyze the available ideas to see which one is the best match for the targeted audience.

Targeting the right audience is crucial when you are developing an app. It saves time when shaping the app in the right direction as you have a clear set of objectives. Likewise, analyzing how the app affects the market is essential. During the research process, App Developers must gather information about potential competitors and threats. This helps the app owners develop strategies to tackle difficulties that come up after the launch.

The research process can take several weeks, but it determines how successful your app can be. For that reason, you must take your time to know all the weaknesses and strengths of the competitors, possible app strategies, and targeted audience.

The outcomes of this stage are app prototypes and the minimum feasible product.

#android app #frontend #ios app #minimum viable product (mvp) #mobile app development #web development #android app development #app development #app development for ios and android #app development process #ios and android app development #ios app development #stages in app development

YuccaPrerenderBundle: Symfony2 Bundle to Use Prerender.io

Yucca/PrerenderBundle

Backbone, EmberJS, Angular and so more are your daily basis ? In case of an admin area, that's fine, but on your front office, you might encounter some SEO problems

Thanks to Prerender.io, you now can dynamically render your JavaScript pages in your server using PhantomJS.

This bundle is largely inspired by bakura10 work on zfr-prerender

Installation

Install the module by typing (or add it to your composer.json file):

$ php composer.phar require "yucca/prerender-bundle" "0.1.*@dev"

Register the bundle in app/AppKernel.php:

// app/AppKernel.php
public function registerBundles()
{
    return array(
        // ...
        new Yucca\PrerenderBundle\YuccaPrerenderBundle(),
    );
}

Enable the bundle's configuration in app/config/config.yml:

# app/config/config.yml
yucca_prerender: ~

Documentation

How it works

  1. Check to make sure we should show a prerendered page
    1. Check if the request is from a crawler (agent string)
    2. Check to make sure we aren't requesting a resource (js, css, etc...)
    3. (optional) Check to make sure the url is in the whitelist
    4. (optional) Check to make sure the url isn't in the blacklist
  2. Make a GET request to the prerender service (PhantomJS server) for the page's prerendered HTML
  3. Return that HTML to the crawler

Customization

This bundle comes with a sane default, extracted from prerender-node middleware, but you can easily customize it:

#app/config/config.yml
yucca_prerender:
    ....

Prerender URL

By default, YuccaPrerenderBundle uses the Prerender.io service deployed at http://prerender.herokuapp.com. However, you may want to deploy it on your own server. To that extent, you can customize YuccaPrerenderBundle to use your server using the following configuration:

#app/config/config.yml
yucca_prerender:
    backend_url: http://localhost:3000

With this config, here is how YuccaPrerender will proxy the "https://google.com" request:

GET http://localhost:3000/https://google.com

Crawler user-agents

YuccaPrerender decides to pre-render based on the User-Agent string to check if a request comes from a bot or not. By default, those user agents are registered: 'baiduspider', 'facebookexternalhit', 'twitterbot'. Googlebot, Yahoo, and Bingbot should not be in this list because we support escaped_fragment instead of checking user agent for those crawlers. Your site must have to understand the '#!' ajax url notation.

You can add other User-Agent string to evaluate using this sample configuration:

#app/config/config.yml
yucca_prerender:
    crawler_user_agents: ['yandex', 'msnbot']

Ignored extensions

YuccaPrerender is configured by default to ignore all the requests for resources with those extensions: .js, .css, .less, .png, .jpg, .jpeg, .gif, .pdf, .doc, .txt, .zip, .mp3, .rar, .exe, .wmv, .doc, .avi, .ppt, .mpg, .mpeg, .tif, .wav, .mov, .psd, .ai, .xls, .mp4, .m4a, .swf, .dat, .dmg, .iso, .flv, .m4v, .torrent . Those are never pre-rendered.

You can add your own extensions using this sample configuration:

#app/config/config.yml
yucca_prerender:
    ignored_extensions: ['.less', '.pdf']

Whitelist

Whitelist a single url path or multiple url paths. Compares using regex, so be specific when possible. If a whitelist is supplied, only url's containing a whitelist path will be prerendered.

Here is a sample configuration that only pre-render URLs that contains "/users/":

#app/config/config.yml
yucca_prerender:
    whitelist_urls: ['/users/*']

Note: remember to specify URL here and not Symfony2 route names.

Blacklist

Blacklist a single url path or multiple url paths. Compares using regex, so be specific when possible. If a blacklist is supplied, all url's will be pre-rendered except ones containing a blacklist part. Please note that if the referer is part of the blacklist, it won't be pre-rendered too.

Here is a sample configuration that prerender all URLs excepting the ones that contains "/users/":

#app/config/config.yml
yucca_prerender:
    blacklist_urls: ['/users/*']

Note: remember to specify URL here and not Symfony22 route names.

Testing

If you want to make sure your pages are rendering correctly:

  1. Open the Developer Tools in Chrome (Cmd + Atl + J)
  2. Click the Settings gear in the bottom right corner.
  3. Click "Overrides" on the left side of the settings panel.
  4. Check the "User Agent" checkbox.
  5. Choose "Other..." from the User Agent dropdown.
  6. Type googlebot into the input box.
  7. Refresh the page (make sure to keep the developer tools open).

Thanks

  • Thanks to bakura10 for the Zend Framework version.
  • Thanks to Romain Boyer to make me discover prerender.io
  • Thanks to the prerender team and all JS MVC developpers

Author: rjanot
Source Code: https://github.com/rjanot/YuccaPrerenderBundle 
License: MIT License

#php #symfony 

ThruwayBundle: Bundle for Building Real-time Apps in Symfony

ThruwayBundle

This a Symfony Bundle for Thruway, which is a php implementation of WAMP (Web Application Messaging Protocol).

Note: This project is still undergoing a lot of changes, so the API will change.

Quick Start with Composer

Install the Thruway Bundle

  $ composer require "voryx/thruway-bundle"

Update AppKernel.php (when using Symfony < 4)

$bundles = array(
    // ...
    new Voryx\ThruwayBundle\VoryxThruwayBundle(),
    // ...
);

Configuration

#app/config/config.yml

voryx_thruway:
    realm: 'realm1'
    url: 'ws://127.0.0.1:8081' #The url that the clients will use to connect to the router
    router:
        ip: '127.0.0.1'  # the ip that the router should start on
        port: '8080'  # public facing port.  If authentication is enabled, this port will be protected
        trusted_port: '8081' # Bypasses all authentication.  Use this for trusted clients.
#        authentication: false # true will load the AuthenticationManager
    locations:
        bundles: ["AppBundle"]
#        files:
#            - "Acme\\DemoBundle\\Controller\\DemoController"
#
# For symfony 4, this bundle will automatically scan for annotated worker files in the src/Controller folder
      

With Symfony 4 use a filename like: config/packages/voryx.yaml

If you are using the in-memory user provider, you'll need to add a thruway to the security firewall and set the in_memory_user_provider.

#app/config/security.yml

security: 
   firewalls:
        thruway:
            security: false	     

You can also tag services with thruway.resource and any annotation will get picked up

<service id="some.service" class="Acme\Bundle\SomeService">
    <tag name="thruway.resource"/>
</service>

Note: tagging a service as thruway.resource will make it public.

services:
    App\Worker\:
        resource: '../src/Worker'
        tags: ['thruway.resource']

Authentication with FOSUserBundle via WampCRA

Change the Password Encoder (tricky on existing sites) to master wamp challenge

#app/config/security.yml

security:
    ...
    encoders:
        FOS\UserBundle\Model\UserInterface:
            algorithm:            pbkdf2
            hash_algorithm:       sha256
            encode_as_base64:     true
            iterations:           1000
            key_length:           32

set voryx_thruway.user_provider to "fos_user.user_provider"

#app/config/config.yml

voryx_thruway:
    user_provider: 'fos_user.user_provider.username' #fos_user.user_provider.username_email login with email

The WAMP-CRA service is already configured, we just need to add a tag to it to have the bundle install it:

    wamp_cra_auth:
        class: Thruway\Authentication\WampCraAuthProvider
        parent: voryx.thruway.wamp.cra.auth.client
        tags:
            - { name: thruway.internal_client }

Custom Authorization Manager

You can set your own Authorization Manager in order to check if a user (identified by its authid) is allowed to publish | subscribe | call | register

Create your Authorization Manager service, extending RouterModuleClient and implementing RealmModuleInterface (see the Thruway doc for details)

// src/ACME/AppBundle/Security/MyAuthorizationManager.php


use Thruway\Event\MessageEvent;
use Thruway\Event\NewRealmEvent;
use Thruway\Module\RealmModuleInterface;
use Thruway\Module\RouterModuleClient;

class MyAuthorizationManager extends RouterModuleClient implements RealmModuleInterface
{
    /**
     * Listen for Router events.
     * Required to add the authorization module to the realm
     *
     * @return array
     */
    public static function getSubscribedEvents()
    {
        return [
            'new_realm' => ['handleNewRealm', 10]
        ];
    }

    /**
     * @param NewRealmEvent $newRealmEvent
     */
    public function handleNewRealm(NewRealmEvent $newRealmEvent)
    {
        $realm = $newRealmEvent->realm;

        if ($realm->getRealmName() === $this->getRealm()) {
            $realm->addModule($this);
        }
    }

    /**
     * @return array
     */
    public function getSubscribedRealmEvents()
    {
        return [
            'PublishMessageEvent'   => ['authorize', 100],
            'SubscribeMessageEvent' => ['authorize', 100],
            'RegisterMessageEvent'  => ['authorize', 100],
            'CallMessageEvent'      => ['authorize', 100],
        ];
    }

    /**
     * @param MessageEvent $msg
     * @return bool
     */
    public function authorize(MessageEvent $msg)
    {
        if ($msg->session->getAuthenticationDetails()->getAuthId() === 'username') {
            return true;
        }
        return false;
    }
}

Register your authorization manager service

     my_authorization_manager:
        class: ACME\AppBundle\Security\MyAuthorizationManager

Insert your service name in the voryx_thruway config

#app/config/config.yml

voryx_thruway:
    ...
        authorization: my_authorization_manager # insert the name of your custom authorizationManager
   ...

Restart the Thruway server; it will now check authorization upon publish | subscribe | call | register. Remember to catch error when you try to subscribe to a topic (or any other action) as it may now be denied and this will be returned as an error.

Usage

Register RPC

    use Voryx\ThruwayBundle\Annotation\Register;
    
    /**
     *
     * @Register("com.example.add")
     *
     */
    public function addAction($num1, $num2)
    {
        return $num1 + $num2;
    }

Call RPC

    public function call($value)
    {
        $client = $this->container->get('thruway.client');
        $client->call("com.myapp.add", [2, 3])->then(
            function ($res) {
                echo $res[0];
            }
        );
    }

Subscribe

     use Voryx\ThruwayBundle\Annotation\Subscribe;

    /**
     *
     * @Subscribe("com.example.subscribe")
     *
     */
    public function subscribe($value)
    {
        echo $value;
    }

Publish

    public function publish($value)
    {
        $client = $this->container->get('thruway.client');
        $client->publish("com.myapp.hello_pubsub", [$value]);
    }

It uses Symfony Serializer, so it can serialize and deserialize Entities

         use Voryx\ThruwayBundle\Annotation\Register;

    /**
     *
     * @Register("com.example.addrpc", serializerEnableMaxDepthChecks=true)
     *
     */
    public function addAction(Post $post)
    {
        //Do something to $post

        return $post;
    }

Start the Thruway Process

You can start the default Thruway workers (router and client workers), without any additional configuration.

$ nohup php app/console thruway:process start &

By default, the router starts on ws://127.0.0.1:8080

Workers

The Thruway bundle will start up a separate process for the router and each defined worker. If you haven't defined any workers, all of the annotated calls and subscriptions will be started within the default worker.

There are two main ways to break your application apart into multiple workers.

Use the worker property on the Register and Subscribe annotations. The following RPC will be added to the posts worker.

  use Voryx\ThruwayBundle\Annotation\Register;

  /**
  * @Register("com.example.addrpc", serializerEnableMaxDepthChecks=true, worker="posts")
  */
  public function addAction(Post $post)

Use the @Worker annotation on the class. The following annotation will create a worker called chat that can have a max of 5 instances.

  use Voryx\ThruwayBundle\Annotation\Worker;

  /**
  * @Worker("chat", maxProcesses="5")
  */
  class ChatController

If a worker is shut down with anything other than SIGTERM, it will automatically be restarted.

More Commands

To see a list of running processes (workers)

$ php app/console thruway:process status

Stop a process, i.e. default

$ php app/console thruway:process stop default

Start a process, i.e. default

$ php app/console thruway:process start default

Javascript Client

For the client, you can use AutobahnJS or any other WAMPv2 compatible client.

Here are some examples

Symfony 4 Quick Start

composer create-project symfony/skeleton my_project
cd my_project
composer require symfony/expression-language
composer require symfony/annotations-pack
composer require voryx/thruway-bundle:dev-master

Create config/packages/my_project.yml with the following config:

voryx_thruway:
    realm: 'realm1'
    url: 'ws://127.0.0.1:8081' #The url that the clients will use to connect to the router
    router:
        ip: '127.0.0.1'  # the ip that the router should start on
        port: '8080'  # public facing port.  If authentication is enabled, this port will be protected
        trusted_port: '8081' # Bypasses all authentication.  Use this for trusted clients.

Create the controller src/Controller/TestController.php

<?php
namespace App\Controller;

use Voryx\ThruwayBundle\Annotation\Register;

class TestController
{
    /**
     * @Register("com.example.add")
     */
    public function addAction($num1, $num2)
    {
        return $num1 + $num2;
    }
}

Test to see if the RPC has been configured correctly bin/console thruway:debug

 URI             Type Worker  File                                                  Method    
 com.example.add RPC  default /my_project/src/Controller/TestController.php         addAction 

For more debug info for the RPC we created: bin/console thruway:debug com.example.add

Start everything: bin/console thruway:process start

The RPC com.example.add is now available to any WAMP client connected to ws://127.0.0.1:8081 on realm1.

Author: Voryx
Source Code: https://github.com/voryx/ThruwayBundle 
License: 

#php #symfony