Level-cache: An in Memory Cache on top Of Leveldb

level-cache

An in memory cache on top of leveldb

Example

Exact same API as levelidb and levelup.

level-cache is one of two things. Either it's a complete in memory copy of the levelup API or it's a cache in front of leveldb.

var level = require("level-cache")

var db = level()
// in memory db

var level = require("level-cache")
    , levelup = require("levelidb")

var db = level(levelup(...))
// cache

level-cache uses lru-cache internally and you can pass in options to configure the internal cache through the API

var level = require("level-cache")

var db = level(db, {
    max: 20000
    , maxAge: 5 * 1000
})

Level cache has a synchronious get API if you don't pass a callback. It will return whatever is in the cache.

var level = require("level-cache")

var db = level(real_db, ...)

...

var value = db.get("key")

Level cache's asynchronous get will hit the cache by default and hit the real database if it doesn't have a value in the cache.

To get level cache to ignore it's local cache in a get just use the cache: false option

var level = require("level-cache")

var db = level(real_db, ...)

...

db.get("key", { cache: false }, function (err, value) {
    // from real db
})

Any callbacks passed to put, del or batch will be passed through to the real leveldb and will come back from the real db.

var level = require("level-cache")

var db = level(real_db, ...)

db.put(key, value)
// real_db.put is called and `db` will emit an `"error"` event
// if real_db returns an error.

db.put(key, value, function (err) {
    // result from real db
})

It should be noted that the readStream() implementation is currently naive. i.e. if a real db is passed to the cache it will just read from the real db and bypass the cache.

level cache only uses the cache with readStream() if you don't pass in a real database.

Kitchen sink example

var level = require("level-cache")
    , toArray = require("write-stream").toArray
    , assert = require("assert")

var db = level()

db.put("foo", { hello: "world" }, function (err) {
    if (err) {
        throw err
    }

    db.get("foo", function (err, value) {
        if (err) {
            throw err
        }

        assert.equal(value.hello, "world")

        console.log("value", value)
    })
})

var ten = makeTen()

db.batch(ten, function (err) {
    if (err) {
        throw err
    }

    var stream = db.readStream({
        start: "batch:"
        , end: "batch;"
    })

    stream.pipe(toArray(function (list) {
        console.log("list", list)

        list.forEach(function (item, index) {
            assert.equal(item.key, ten[index].key)
            assert.equal(item.value, ten[index].value)
        })
    }))

    var keyStream = db.keyStream({
        start: "batch:"
        , end: "batch;"
    })

    keyStream.pipe(toArray(function (list) {
        console.log("keys", list)

        list.forEach(function (item, index) {
            assert.equal(item, ten[index].key)
        })
    }))

    var valueStream = db.valueStream({
        start: "batch:"
        , end: "batch;"
    })

    valueStream.pipe(toArray(function (list) {
        list.forEach(function (item, index) {
            assert.equal(item, ten[index].value)
        })

        console.log("values", list)
    }))
})

var writable = db.writeStream()

writable.write({ key: "write:05", value: "5" })
writable.write({ key: "write:20", value: "20" })

writable.end()
writable.on("finish", function () {
    console.log("finished writing")

    var readable = db.valueStream({
        start: "write:"
        , end: "write;"
    })

    readable.pipe(toArray(function (list) {
        assert.equal(list[0], "5")
        assert.equal(list[1], "20")
        assert.equal(list.length, 2)

        console.log("values from writeStream", list)
    }))
})

function makeTen() {
    var list = []
    for (var i = 0; i < 10; i++) {
        list.push({
            type: "put"
            , key: "batch:" + i
            , value: i
        })
    }
    return list
}

Installation

npm install level-cache

Contributors

Raynos

Author: Raynos
Source Code: https://github.com/Raynos/level-cache
License: MIT license

#javascript #cache #node #leveldb

Level-cache: An in Memory Cache on top Of Leveldb

level-cache

An in memory cache on top of leveldb

Example

Exact same API as levelidb and levelup.

level-cache is one of two things. Either it's a complete in memory copy of the levelup API or it's a cache in front of leveldb.

var level = require("level-cache")

var db = level()
// in memory db

var level = require("level-cache")
    , levelup = require("levelidb")

var db = level(levelup(...))
// cache

level-cache uses lru-cache internally and you can pass in options to configure the internal cache through the API

var level = require("level-cache")

var db = level(db, {
    max: 20000
    , maxAge: 5 * 1000
})

Level cache has a synchronious get API if you don't pass a callback. It will return whatever is in the cache.

var level = require("level-cache")

var db = level(real_db, ...)

...

var value = db.get("key")

Level cache's asynchronous get will hit the cache by default and hit the real database if it doesn't have a value in the cache.

To get level cache to ignore it's local cache in a get just use the cache: false option

var level = require("level-cache")

var db = level(real_db, ...)

...

db.get("key", { cache: false }, function (err, value) {
    // from real db
})

Any callbacks passed to put, del or batch will be passed through to the real leveldb and will come back from the real db.

var level = require("level-cache")

var db = level(real_db, ...)

db.put(key, value)
// real_db.put is called and `db` will emit an `"error"` event
// if real_db returns an error.

db.put(key, value, function (err) {
    // result from real db
})

It should be noted that the readStream() implementation is currently naive. i.e. if a real db is passed to the cache it will just read from the real db and bypass the cache.

level cache only uses the cache with readStream() if you don't pass in a real database.

Kitchen sink example

var level = require("level-cache")
    , toArray = require("write-stream").toArray
    , assert = require("assert")

var db = level()

db.put("foo", { hello: "world" }, function (err) {
    if (err) {
        throw err
    }

    db.get("foo", function (err, value) {
        if (err) {
            throw err
        }

        assert.equal(value.hello, "world")

        console.log("value", value)
    })
})

var ten = makeTen()

db.batch(ten, function (err) {
    if (err) {
        throw err
    }

    var stream = db.readStream({
        start: "batch:"
        , end: "batch;"
    })

    stream.pipe(toArray(function (list) {
        console.log("list", list)

        list.forEach(function (item, index) {
            assert.equal(item.key, ten[index].key)
            assert.equal(item.value, ten[index].value)
        })
    }))

    var keyStream = db.keyStream({
        start: "batch:"
        , end: "batch;"
    })

    keyStream.pipe(toArray(function (list) {
        console.log("keys", list)

        list.forEach(function (item, index) {
            assert.equal(item, ten[index].key)
        })
    }))

    var valueStream = db.valueStream({
        start: "batch:"
        , end: "batch;"
    })

    valueStream.pipe(toArray(function (list) {
        list.forEach(function (item, index) {
            assert.equal(item, ten[index].value)
        })

        console.log("values", list)
    }))
})

var writable = db.writeStream()

writable.write({ key: "write:05", value: "5" })
writable.write({ key: "write:20", value: "20" })

writable.end()
writable.on("finish", function () {
    console.log("finished writing")

    var readable = db.valueStream({
        start: "write:"
        , end: "write;"
    })

    readable.pipe(toArray(function (list) {
        assert.equal(list[0], "5")
        assert.equal(list[1], "20")
        assert.equal(list.length, 2)

        console.log("values from writeStream", list)
    }))
})

function makeTen() {
    var list = []
    for (var i = 0; i < 10; i++) {
        list.push({
            type: "put"
            , key: "batch:" + i
            , value: i
        })
    }
    return list
}

Installation

npm install level-cache

Contributors

Raynos

Author: Raynos
Source Code: https://github.com/Raynos/level-cache
License: MIT license

#javascript #cache #node #leveldb

Lokesh Kumar

1603438098

Top 10 Trending Technologies Must Learn in 2021 | igmGuru

Technology has taken a place of more productiveness and give the best to the world. In the current situation, everything is done through the technical process, you don’t have to bother about doing task, everything will be done automatically.This is an article which has some important technologies which are new in the market are explained according to the career preferences. So let’s have a look into the top trending technologies followed in 2021 and its impression in the coming future in the world.

Data Science
First in the list of newest technologies is surprisingly Data Science. Data Science is the automation that helps to be reasonable for complicated data. The data is produces in a very large amount every day by several companies which comprise sales data, customer profile information, server data, business data, and financial structures. Almost all of the data which is in the form of big data is very indeterminate. The character of a data scientist is to convert the indeterminate datasets into determinate datasets. Then these structured data will examine to recognize trends and patterns. These trends and patterns are beneficial to understand the company’s business performance, customer retention, and how they can be enhanced.
DevOps
Next one is DevOps, This technology is a mixture of two different things and they are development (Dev) and operations (Ops). This process and technology provide value to their customers in a continuous manner. This technology plays an important role in different aspects and they can be- IT operations, development, security, quality, and engineering to synchronize and cooperate to develop the best and more definitive products. By embracing a culture of DevOps with creative tools and techniques, because through that company will gain the capacity to preferable comeback to consumer requirement, expand the confidence in the request they construct, and accomplish business goals faster. This makes DevOps come into the top 10 trending technologies.
Machine learning
Next one is Machine learning which is constantly established in all the categories of companies or industries, generating a high command for skilled professionals. The machine learning retailing business is looking forward to enlarging to $8.81 billion by 2022. Machine learning practices is basically use for data mining, data analytics, and pattern recognition. In today’s scenario, Machine learning has its own reputed place in the industry. This makes machine learning come into the top 10 trending technologies. Get the best machine learning course and make yourself future-ready.

To want to know more click on Top 10 Trending Technologies in 2021

You may also read more blogs mentioned below

How to Become a Salesforce Developer

Python VS R Programming

The Scope of Hadoop and Big Data in 2021

#top trending technologies #top 10 trending technologies #top 10 trending technologies in 2021 #top trending technologies in 2021 #top 5 trending technologies in 2021 #top 5 trending technologies

Lawrence Lesch

1658004900

Prerender-level-cache: Prerender Plugin for Level Caching

prerender-level-cache

Prerender plugin for level caching, to be used with the prerender node application

How it works

This plugin will store all prerendered pages into LevelDB.

How to use

In your local prerender project run:

$ npm install prerender-level-cache

Then in the server.js that initializes the prerender:

server.use(require('prerender-level-cache'));

Features

Ttl

It uses a default ttl of 2 months, but that can be overridden by setting a different value in prerender server.options.ttl.

Refresh

You can force a refresh from another plugin by setting req.refresh = true

Exemple:

// in another plugin placed before prerender-level-cache
module.exports = {
  requestReceived: (req, res, next) => {
    req.refresh = true
    next()
  }
}

Alternatively, you can delete the cache directly in the LevelDB database, using a tool such as lev2.

Level-party

The plugin uses the level-party module to get over the level multi-process restrictions.

Author: Maxlath
Source Code: https://github.com/maxlath/prerender-level-cache
License: MIT license

#javascript #cache #node #leveldb

Josefa Corwin

1659852060

A Template Language That Completely Separates Structure and Logic/Ruby

Curly

Curly is a template language that completely separates structure and logic. Instead of interspersing your HTML with snippets of Ruby, all logic is moved to a presenter class.

Installing

Installing Curly is as simple as running gem install curly-templates. If you're using Bundler to manage your dependencies, add this to your Gemfile

gem 'curly-templates'

Curly can also install an application layout file, replacing the .erb file commonly created by Rails. If you wish to use this, run the curly:install generator.

$ rails generate curly:install

How to use Curly

In order to use Curly for a view or partial, use the suffix .curly instead of .erb, e.g. app/views/posts/_comment.html.curly. Curly will look for a corresponding presenter class named Posts::CommentPresenter. By convention, these are placed in app/presenters/, so in this case the presenter would reside in app/presenters/posts/comment_presenter.rb. Note that presenters for partials are not prepended with an underscore.

Add some HTML to the partial template along with some Curly components:

<!-- app/views/posts/_comment.html.curly -->
<div class="comment">
  <p>
    {{author_link}} posted {{time_ago}} ago.
  </p>

  {{body}}

  {{#author?}}
    <p>{{deletion_link}}</p>
  {{/author?}}
</div>

The presenter will be responsible for providing the data for the components. Add the necessary Ruby code to the presenter:

# app/presenters/posts/comment_presenter.rb
class Posts::CommentPresenter < Curly::Presenter
  presents :comment

  def body
    SafeMarkdown.render(@comment.body)
  end

  def author_link
    link_to @comment.author.name, @comment.author, rel: "author"
  end

  def deletion_link
    link_to "Delete", @comment, method: :delete
  end

  def time_ago
    time_ago_in_words(@comment.created_at)
  end

  def author?
    @comment.author == current_user
  end
end

The partial can now be rendered like any other, e.g. by calling

render 'comment', comment: comment
render comment
render collection: post.comments

Curly components are surrounded by curly brackets, e.g. {{hello}}. They always map to a public method on the presenter class, in this case #hello. Methods ending in a question mark can be used for conditional blocks, e.g. {{#admin?}} ... {{/admin?}}.

Identifiers

Curly components can specify an identifier using the so-called dot notation: {{x.y.z}}. This can be very useful if the data you're accessing is hierarchical in nature. One common example is I18n:

<h1>{{i18n.homepage.header}}</h1>

# In the presenter, the identifier is passed as an argument to the method. The
# argument will always be a String.
def i18n(key)
  translate(key)
end

The identifier is separated from the component name with a dot. If the presenter method has a default value for the argument, the identifier is optional – otherwise it's mandatory.

Attributes

In addition to an identifier, Curly components can be annotated with attributes. These are key-value pairs that affect how a component is rendered.

The syntax is reminiscent of HTML:

<div>{{sidebar rows=3 width=200px title="I'm the sidebar!"}}</div>

The presenter method that implements the component must have a matching keyword argument:

def sidebar(rows: "1", width: "100px", title:); end

All argument values will be strings. A compilation error will be raised if

an attribute is used in a component without a matching keyword argument being present in the method definition; or
a required keyword argument in the method definition is not set as an attribute in the component.

You can define default values using Ruby's own syntax. Additionally, if the presenter method accepts arbitrary keyword arguments using the **doublesplat syntax then all attributes will be valid for the component, e.g.

def greetings(**names)
  names.map {|name, greeting| "#{name}: #{greeting}!" }.join("\n")
end

{{greetings alice=hello bob=hi}}
<!-- The above would be rendered as: -->
alice: hello!
bob: hi!

Note that since keyword arguments in Ruby are represented as Symbol objects, which are not garbage collected in Ruby versions less than 2.2, accepting arbitrary attributes represents a security vulnerability if your application allows untrusted Curly templates to be rendered. Only use this feature with trusted templates if you're not on Ruby 2.2 yet.

Conditional blocks

If there is some content you only want rendered under specific circumstances, you can use conditional blocks. The {{#admin?}}...{{/admin?}} syntax will only render the content of the block if the admin? method on the presenter returns true, while the {{^admin?}}...{{/admin?}} syntax will only render the content if it returns false.

Both forms can have an identifier: {{#locale.en?}}...{{/locale.en?}} will only render the block if the locale? method on the presenter returns true given the argument "en". Here's how to implement that method in the presenter:

class SomePresenter < Curly::Presenter
  # Allows rendering content only if the locale matches a specified identifier.
  def locale?(identifier)
    current_locale == identifier
  end
end

Furthermore, attributes can be set on the block. These only need to be specified when opening the block, not when closing it:

{{#square? width=3 height=3}}
  <p>It's square!</p>
{{/square?}}

Attributes work the same way as they do for normal components.

Collection blocks

Sometimes you want to render one or more items within the current template, and splitting out a separate template and rendering that in the presenter is too much overhead. You can instead define the template that should be used to render the items inline in the current template using the collection block syntax.

Collection blocks are opened using an asterisk:

{{*comments}}
  <li>{{body}} ({{author_name}})</li>
{{/comments}}

The presenter will need to expose the method #comments, which should return a collection of objects:

class Posts::ShowPresenter < Curly::Presenter
  presents :post

  def comments
    @post.comments
  end
end

The template within the collection block will be used to render each item, and it will be backed by a presenter named after the component – in this case, comments. The name will be singularized and Curly will try to find the presenter class in the following order:

Posts::ShowPresenter::CommentPresenter
Posts::CommentPresenter
CommentPresenter

This allows you some flexibility with regards to how you want to organize these nested templates and presenters.

Note that the nested template will only have access to the methods on the nested presenter, but all variables passed to the "parent" presenter will be forwarded to the nested presenter. In addition, the current item in the collection will be passed, as well as that item's index in the collection:

class Posts::CommentPresenter < Curly::Presenter
  presents :post, :comment, :comment_counter

  def number
    # `comment_counter` is automatically set to the item's index in the collection,
    # starting with 1.
    @comment_counter
  end

  def body
    @comment.body
  end

  def author_name
    @comment.author.name
  end
end

Collection blocks are an alternative to splitting out a separate template and rendering that from the presenter – which solution is best depends on your use case.

Context blocks

While collection blocks allow you to define the template that should be used to render items in a collection right within the parent template, context blocks allow you to define the template for an arbitrary context. This is very powerful, and can be used to define widget-style components and helpers, and provide an easy way to work with structured data. Let's say you have a comment form on your page, and you'd rather keep the template inline. A simple template could look like:

<!-- post.html.curly -->
<h1>{{title}}</h1>
{{body}}

{{@comment_form}}
  <b>Name: </b> {{name_field}}<br>
  <b>E-mail: </b> {{email_field}}<br>
  {{comment_field}}

  {{submit_button}}
{{/comment_form}}

Note that an @ character is used to denote a context block. Like with collection blocks, a separate presenter class is used within the block, and a simple convention is used to find it. The name of the context component (in this case, comment_form) will be camel cased, and the current presenter's namespace will be searched:

class PostPresenter < Curly::Presenter
  presents :post
  def title; @post.title; end
  def body; markdown(@post.body); end

  # A context block method *must* take a block argument. The return value
  # of the method will be used when rendering. Calling the block argument will
  # render the nested template. If you pass a value when calling the block
  # argument it will be passed to the presenter.
  def comment_form(&block)
    form_for(Comment.new, &block)
  end

  # The presenter name is automatically deduced.
  class CommentFormPresenter < Curly::Presenter
    # The value passed to the block argument will be passed in a parameter named
    # after the component.
    presents :comment_form

    # Any parameters passed to the parent presenter will be forwarded to this
    # presenter as well.
    presents :post

    def name_field
      @comment_form.text_field :name
    end

    # ...
  end
end

Context blocks were designed to work well with Rails' helper methods such as form_for and content_tag, but you can also work directly with the block. For instance, if you want to directly control the value that is passed to the nested presenter, you can call the call method on the block yourself:

def author(&block)
  content_tag :div, class: "author" do
    # The return value of `call` will be the result of rendering the nested template
    # with the argument. You can post-process the string if you want.
    block.call(@post.author)
  end
end

Context shorthand syntax

If you find yourself opening a context block just in order to use a single component, e.g. {{@author}}{{name}}{{/author}}, you can use the shorthand syntax instead: {{author:name}}. This works for all component types, e.g.

{{#author:admin?}}
  <p>The author is an admin!</p>
{{/author:admin?}}

The syntax works for nested contexts as well, e.g. {{comment:author:name}}. Any identifier and attributes are passed to the target component, which in this example would be {{name}}.

Setting up state

Although most code in Curly presenters should be free of side effects, sometimes side effects are required. One common example is defining content for a content_for block.

If a Curly presenter class defines a setup! method, it will be called before the view is rendered:

class PostPresenter < Curly::Presenter
  presents :post

  def setup!
    content_for :title, post.title

    content_for :sidebar do
      render 'post_sidebar', post: post
    end
  end
end

Escaping Curly syntax

In order to have {{ appear verbatim in the rendered HTML, use the triple Curly escape syntax:

This is {{{escaped}}.

You don't need to escape the closing }}.

Comments

If you want to add comments to your Curly templates that are not visible in the rendered HTML, use the following syntax:

{{! This is some interesting stuff }}

Presenters

Presenters are classes that inherit from Curly::Presenter – they're usually placed in app/presenters/, but you can put them anywhere you'd like. The name of the presenter classes match the virtual path of the view they're part of, so if your controller is rendering posts/show, the Posts::ShowPresenter class will be used. Note that Curly is only used to render a view if a template can be found – in this case, at app/views/posts/show.html.curly.

Presenters can declare a list of accepted variables using the presents method:

class Posts::ShowPresenter < Curly::Presenter
  presents :post
end

A variable can have a default value:

class Posts::ShowPresenter < Curly::Presenter
  presents :post
  presents :comment, default: nil
end

Any public method defined on the presenter is made available to the template as a component:

class Posts::ShowPresenter < Curly::Presenter
  presents :post

  def title
    @post.title
  end

  def author_link
    # You can call any Rails helper from within a presenter instance:
    link_to author.name, profile_path(author), rel: "author"
  end

  private

  # Private methods are not available to the template, so they're safe to
  # use.
  def author
    @post.author
  end
end

Presenter methods can even take an argument. Say your Curly template has the content {{t.welcome_message}}, where welcome_message is an I18n key. The following presenter method would make the lookup work:

def t(key)
  translate(key)
end

That way, simple ``functions'' can be added to the Curly language. Make sure these do not have any side effects, though, as an important part of Curly is the idempotence of the templates.

Layouts and content blocks

Both layouts and content blocks (see content_for) use yield to signal that content can be inserted. Curly works just like ERB, so calling yield with no arguments will make the view usable as a layout, while passing a Symbol will make it try to read a content block with the given name:

# Given you have the following Curly template in
# app/views/layouts/application.html.curly
#
#   <html>
#     <head>
#       <title>{{title}}</title>
#     </head>
#     <body>
#       <div id="sidebar">{{sidebar}}</div>
#       {{body}}
#     </body>
#   </html>
#
class ApplicationLayout < Curly::Presenter
  def title
    "You can use methods just like in any other presenter!"
  end

  def sidebar
    # A view can call `content_for(:sidebar) { "some HTML here" }`
    yield :sidebar
  end

  def body
    # The view will be rendered and inserted here:
    yield
  end
end

Rails helper methods

In order to make a Rails helper method available as a component in your template, use the exposes_helper method:

class Layouts::ApplicationPresenter < Curly::Presenter
  # The components {{sign_in_path}} and {{root_path}} are made available.
  exposes_helper :sign_in_path, :root_path
end

Testing

Presenters can be tested directly, but sometimes it makes sense to integrate with Rails on some levels. Currently, only RSpec is directly supported, but you can easily instantiate a presenter:

SomePresenter.new(context, assigns)

context is a view context, i.e. an object that responds to render, has all the helper methods you expect, etc. You can pass in a test double and see what you need to stub out. assigns is the hash containing the controller and local assigns. You need to pass in a key for each argument the presenter expects.

Testing with RSpec

In order to test presenters with RSpec, make sure you have rspec-rails in your Gemfile. Given the following presenter:

# app/presenters/posts/show_presenter.rb
class Posts::ShowPresenter < Curly::Presenter
  presents :post

  def body
    Markdown.render(@post.body)
  end
end

You can test the presenter methods like this:

# You can put this in your `spec_helper.rb`.
require 'curly/rspec'

# spec/presenters/posts/show_presenter_spec.rb
describe Posts::ShowPresenter, type: :presenter do
  describe "#body" do
    it "renders the post's body as Markdown" do
      assign(:post, double(:post, body: "**hello!**"))
      expect(presenter.body).to eq "<strong>hello!</strong>"
    end
  end
end

Note that your spec must be tagged with type: :presenter.

Examples

Here is a simple Curly template – it will be looked up by Rails automatically.

<!-- app/views/posts/show.html.curly -->
<h1>{{title}}<h1>
<p class="author">{{author}}</p>
<p>{{description}}</p>

{{comment_form}}

<div class="comments">
  {{comments}}
</div>

When rendering the template, a presenter is automatically instantiated with the variables assigned in the controller or the render call. The presenter declares the variables it expects with presents, which takes a list of variables names.

# app/presenters/posts/show_presenter.rb
class Posts::ShowPresenter < Curly::Presenter
  presents :post

  def title
    @post.title
  end

  def author
    link_to(@post.author.name, @post.author, rel: "author")
  end

  def description
    Markdown.new(@post.description).to_html.html_safe
  end

  def comments
    render 'comment', collection: @post.comments
  end

  def comment_form
    if @post.comments_allowed?
      render 'comment_form', post: @post
    else
      content_tag(:p, "Comments are disabled for this post")
    end
  end
end

Caching

Caching is handled at two levels in Curly – statically and dynamically. Static caching concerns changes to your code and templates introduced by deploys. If you do not wish to clear your entire cache every time you deploy, you need a way to indicate that some view, helper, or other piece of logic has changed.

Dynamic caching concerns changes that happen on the fly, usually made by your users in the running system. You wish to cache a view or a partial and have it expire whenever some data is updated – usually whenever a specific record is changed.

Dynamic Caching

Because of the way logic is contained in presenters, caching entire views or partials by the data they present becomes exceedingly straightforward. Simply define a #cache_key method that returns a non-nil object, and the return value will be used to cache the template.

Whereas in ERB you would include the cache call in the template itself:

<% cache([@post, signed_in?]) do %>
  ...
<% end %>

In Curly you would instead declare it in the presenter:

class Posts::ShowPresenter < Curly::Presenter
  presents :post

  def cache_key
    [@post, signed_in?]
  end
end

Likewise, you can add a #cache_duration method if you wish to automatically expire the fragment cache:

class Posts::ShowPresenter < Curly::Presenter
  ...

  def cache_duration
    30.minutes
  end
end

In order to set any cache option, define a #cache_options method that returns a Hash of options:

class Posts::ShowPresenter < Curly::Presenter
  ...

  def cache_options
    { compress: true, namespace: "my-app" }
  end
end

Static Caching

Static caching will only be enabled for presenters that define a non-nil #cache_key method (see Dynamic Caching.)

In order to make a deploy expire the cache for a specific view, set the version of the view to something new, usually by incrementing by one:

class Posts::ShowPresenter < Curly::Presenter
  version 3

  def cache_key
    # Some objects
  end
end

This will change the cache keys for all instances of that view, effectively expiring the old cache entries.

This works well for views, or for partials that are rendered in views that themselves are not cached. If the partial is nested within a view that is cached, however, the outer cache will not be expired. The solution is to register that the inner partial is a dependency of the outer one such that Curly can automatically deduce that the outer partial cache should be expired:

class Posts::ShowPresenter < Curly::Presenter
  version 3
  depends_on 'posts/comment'

  def cache_key
    # Some objects
  end
end

class Posts::CommentPresenter < Curly::Presenter
  version 4

  def cache_key
    # Some objects
  end
end

Now, if the version of Posts::CommentPresenter is bumped, the cache keys for both presenters would change. You can register any number of view paths with depends_on.

Curly integrates well with the caching mechanism in Rails 4 (or Cache Digests in Rails 3), so the dependencies defined with depends_on will be tracked by Rails. This will allow you to deploy changes to your templates and have the relevant caches automatically expire.

Thanks

Thanks to Zendesk for sponsoring the work on Curly.

Contributors

Daniel Schierbeck (@dasch)
Benjamin Quorning (@bquorning)
Jeremy Rodi (@medcat)
Alisson Cavalcante Agiani (@thelinuxlich)
Łukasz Niemier (@hauleth)
Cristian Planas (@Gawyn)
Steven Davidovitz (@steved)

Build Status

Author: zendesk
Source code: https://github.com/zendesk/curly

#ruby #ruby-on-rails

davis mike

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Identifiers

Attributes

Conditional blocks

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