Elastic Load Balancing

What is load balancing?

• Load balancers are servers that forward internet traffic to multiple server (EC2 Instances) downstream.

Why use a load balancer?

• Spread load across multiple downstream instances.
• Expose a single point of access (DNS) to your application.
• Seamlessly handle failures of downstream instances.
• Do regular health checks to your instances.
• → If one of them is failing then the load balancer will not direct traffic to the instance, so we can hide the failure of an EC2 instance using a load balancer.
• Provide SSL termination (HTTPS) for your websites.
• High availability across zones.

#aws #load-balancer #instance #elastic-load-balancer #data-engineer

What is GEEK

Buddha Community

Elastic Load Balancing

What is load balancing?

• Load balancers are servers that forward internet traffic to multiple server (EC2 Instances) downstream.

Why use a load balancer?

• Spread load across multiple downstream instances.
• Expose a single point of access (DNS) to your application.
• Seamlessly handle failures of downstream instances.
• Do regular health checks to your instances.
• → If one of them is failing then the load balancer will not direct traffic to the instance, so we can hide the failure of an EC2 instance using a load balancer.
• Provide SSL termination (HTTPS) for your websites.
• High availability across zones.

#aws #load-balancer #instance #elastic-load-balancer #data-engineer

Sample Load balancing solution with Docker and Nginx

Most of today’s business applications use load balancing to distribute traffic among different resources and avoid overload of a single resource.

One of the obvious advantages of load balancing architecture is to increase the availability and reliability of applications, so if a certain number of clients request some number of resources to backends, Load balancer stays between them and route the traffic to the backend that fills most the routing criteria (less busy, most healthy, located in a given region … etc).

There are a lot of routing criteria, but we will focus on this article on fixed round-robin criteria — meaning each backend receives a fixed amount of traffic — which I think rarely documented :).

To simplify we will create two backends “applications” based on flask Python files. We will use NGINX as a load balancer to distribute 60% of traffic to application1 and 40% of traffic to application2.

Let’s start the coding, hereafter the complete architecture of our project:

app1/app1.py

from flask import request, Flask
import json

app1 = Flask(__name__)
@app1.route('/')
def hello_world():
return 'Salam alikom, this is App1 :) '
if __name__ == '__main__':
app1.run(debug=True, host='0.0.0.0')

app2/app2.py

from flask import request, Flask
import json

app1 = Flask(__name__)
@app1.route('/')
def hello_world():
return 'Salam alikom, this is App2 :) '
if __name__ == '__main__':
app1.run(debug=True, host='0.0.0.0')

Then we have to dockerize both applications by adding the requirements.txt file. It will contain only the flask library since we are using the python3 image.

#load-balancing #python-flask #docker-load-balancing #nginx #flask-load-balancing

AWS Application Load Balancer vs. NGINX Plus

In August 2016, Amazon Web Services (AWS) introduced Application Load Balancer for Layer 7 load balancing of HTTP and HTTPS traffic. The new product added several features missing from AWS’s existing Layer 4 and Layer 7 load balancer, Elastic Load Balancer, which was officially renamed Classic Load Balancer.

A year later, AWS launched Network Load Balancer for improved Layer 4 load balancing, so the set of choices for users running highly available, scalable applications on AWS includes:

• NGINX Open Source and NGINX Plus
• Classic Load Balancer
• Application Load Balancer (ALB)
• Network Load Balancer (NLB)

In this post, we review ALB’s features and compare its pricing and features to NGINX Open Source and NGINX Plus.

Notes –

• The information about supported features is accurate as of July 2020, but is subject to change.
• For a direct comparison of NGINX Plus and Classic Load Balancer (formerly Elastic Load Balancer or ELB), as well as information on using them together, see our previous blog post.
• For information on using NLB for a high‑availability NGINX Plus deployment, see our previous blog post.

Features In Application Load Balancer

ALB, like Classic Load Balancer or NLB, is tightly integrated into AWS. Amazon describes it as a Layer 7 load balancer – though it does not provide the full breadth of features, tuning, and direct control that a standalone Layer 7 reverse proxy and load balancer can offer.

ALB provides the following features that are missing from Classic Load Balancer:

• Content‑based routing. ALB supports content‑based routing based on the request URL, Host header, and fields in the request that include standard and custom HTTP headers and methods, query parameters, and source IP address. (See “Benefits of migrating from a Classic Load Balancer” in the ALB documentation.)
• Support for container‑based applications. ALB improves on the existing support for containers hosted on Amazon’s EC2 Container Service (ECS).
• More metrics. You can collect metrics on a per‑microservice basis.
• WebSocket support. ALB supports persistent TCP connections between a client and server.
• HTTP/2 support. ALB supports HTTP/2, a superior alternative when delivering content secured by SSL/TLS.

(For a complete feature comparison of ALB and Classic Load Balancer, see “Product comparisons” in the AWS documentation.)

ALB was a significant update for AWS users who had struggled with Classic Load Balancer’s limited feature set, and it went some way towards addressing the requirements of sophisticated users who need to be able to secure, optimize, and control the traffic to their web applications. However, it still does not provide all the capabilities of dedicated reverse proxies (such as NGINX) and load balancers (such as NGINX Plus).

#load balancing #elastic load balancing (elb) #amazon web services #aws

[アップデート] Network Load Balancer で TLS ALPN がサポートされたので HTTP/2 が可能になりました。

何が嬉しいのか

TLS リスナーで HTTP/2 が利用可能に

これまで NLB の TLS リスナーでは ALPN に対応していなかったため、HTTP/2 で受けることが出来ませんでした。そのため、NLB を介した HTTP/2 通信をするには TLS リスナーではなく TCP リスナーとして NLB を構成する必要がありました。

この場合、NLB は TCP パススルーとしてのみ機能しますので、TLS ネゴシエーションや、TLS の暗号化/復号といった処理は NLB のターゲットとなるサーバー側で行うこととなり、少なからず TLS 通信のための負荷が掛かることになります。

今回、gRPC は試していませんが、従来であれば以下の記事のように TCP リスナーとしてエンドツーエンドでの TLS ネゴシエーションだったところを、NLB の TLS リスナーで対応できるようになるかと思います。

ちなみに ALB の場合は、ALPN に対応していますが、ALB が HTTP/2 を HTTP/1.1 に変換してターゲットグループに流しますので、gRPC などは利用できません。

Application Load Balancer は、HTTPS リスナーに HTTP/2 のネイティブサポートを提供します。1 つの HTTP/2 コネクションで最大 128 のリクエストを並行して送信できます。ロードバランサーは、これらのリクエストを個々の HTTP/1.1 のリクエストに変換し、ターゲットグループの正常なターゲットにこれを分配します。

（引用：Application Load Balancer のリスナー）

TLS リスナーで終端は出来ない！？

今回のアップデートを見たとき、TLS リスナーで終端できるのだろうと思っていたのですが、ALPN ポリシーを利用する場合は、TLS リスナーに加えて TLS ターゲットグループが必須要件となっていますので、ターゲット側でも何らかの証明書が必要なようです。

#aws #aws elastic load balancing #network load balancer

AOL Emails Not Loading Problems (+1-888-857-5157) in Chrome Browser

AOL Mail is one of the free email services that includes calendar management and task management. If your AOL Emails Not Loading Problems in Chrome Browser, try these troubleshooting steps which is mention below. In this post, we are trying to describe the reason behind AOL email not loading and how to resolve AOL mail loading issues.

3 Reason Behind AOL Emails Not Loading Problems

Reason #1. Whenever you are unable to receive the new emails into your computer. You should log into your AOL mail account and go to the settings and click on filter settings. Now check the account settings, if you find any filter. you need to click on delete. After deleting the settings, you should send a mail to yourself. Let’s see if you are receiving it now or not.

Reason #2. If you do not find any filters into your emails, you should check the block list settings, maybe you have blocked the new emails from senders. That’s why you are not receiving any new emails. so, you should immediately go ahead and check it.

Reason #3. If you are unable to receive the new emails into your phone or computer. I would like to suggest you to check the server settings. Most of the time, people are facing such kind of problem due to the incorrect server settings. So, you should check them properly and if you find something wrong over there. You need to remove the account from your computer or phone and then reconfigure it. It will start working fine.

How to Resolve AOL Emails Not Loading Problems in Chrome Browser

If Your AOL Emails Not Loading Problems in Chrome Browser then you can go and find a help to resolve this issue. To get through this problem, follow the instructions below:

Solution 1: Clear browsing data on Chrome

• On your computer, launch the Google Chrome browser after assuring that you have a stable Internet connection.
• Close all the browser tabs (if any) and open a new blank tab.
• Click the Customize and control Google Chrome icon at the top-right corner and select the More tools option from the drop-down list.
• In the pop-up window, navigate to the top-left corner and click the clear browsing data tab beneath History.
• When you are asked to choose the time limit, choose the Time
• After choosing all the data, click the Clear data button to remove all your Chrome browsing data.
• Once you have removed all the browsing data, sign in to your AOL Mail.
• If your AOL Mail is still not loading on Chrome, move on to the next solution.

Solution 2: Reset web settings

• On your Chrome browser, stop all the running tabs and start a blank tab.
• Navigate to the top-right corner of the tab and click the Customize and control Google Chrome icon (three vertical dots).
• Click on Settings from the drop-down list.
• Navigate to the bottom of the Settings page and click Advanced.
• Click the Reset Settings tab twice underneath Reset and clean up.
• Now, your Chrome browser will be restored to factory defaults.
• Restart your Chrome browser and navigate to the official AOL site.
• Enter the correct login credentials in the essential field and try signing in to your AOL email account.
  If AOL Mail is still not loading on Chrome, contact our technical support team by clicking the Call button available on this page for remote assistance.
  After this, if you are unable to resolve AOL emails loading problems in chrome browser, don’t be panic. Email Expert 24*7 team is here to resolve all AOL mail issues as soon as possible. Just Dial Customer Care Toll-Free Number: +1-888-857-5157 and get instant help. Our technical team’s services are available- 24x7.

Source: https://email-expert247.blogspot.com/2021/01/aol-emails-not-loading-problems-1-888.html

#aol mail not loading problems in chrome browser #aol email not loading problems in chrome browser #aol not loading problems in chrome browser #aol mail not loading issues in chrome browser #aol email not loading issues in chrome browser