Publisher/Subscriber Model

Publish/subscribe messaging, or pub/sub messaging, is a form of asynchronous service-to-service communication used in serverless and microservices architectures. In a pub/sub model, any message published to a topic is immediately received by all of the subscribers to the topic. Pub/sub messaging can be used to enable event-driven architectures, or to decouple applications in order to increase performance, reliability and scalability.

Depending on which pub/sub technology you end up choosing, your application code will be tightly coupled the technology you choose, which makes it difficult to switch from one provider to another without changing the code of your application

DAPR ( Distributed APplication Runtime) give your the possibility to abstract your pub/sub layer and write your code independently of your pub/sub provider ( SQS, Azure Bus Service, Kafka, Azure event hub, rabbitmq, redis streams )

Example :

In this example we will have an order processing app where the publisher pushers orders to the messaging queue

Application Layer : Publisher and Subscriber both python programs

DAPR pubsub Component : we will use Azure Service Bus

1- creating Azure Service Bus :

for more details about how to create an Azure Service Bus, you can read this article

2- Install Dapr

curl -fsSL https://raw.githubusercontent.com/dapr/cli/master/install/install.sh | /bin/bash

3- initialize dapr

in a terminal window run : dapr init

4- configure dapr publisher component

create a yaml file called pubsub.yaml and place it under ~/.dapr/components

View this gist on GitHub

dapr run --app-id daprapptest --dapr-http-port 3601

6- Run publisher application

save the following app code to a publisher.py file

View this gist on GitHub

Starting the publisher app :

dapr run --app-id daprapptest --app-port 6001 --dapr-http-port 3601 --app-protocol grpc python3 publisher.py

The application start publishing messages to the Azure Service Bus

My Thoughts:

Modern microservices cloud-native applications need to be able to agnostic of the underlying technologies in order to achieve more independence and ease of deployment across platforms, in the example above we tied to make a publisher application code more independent of the technology, we used Azure Service Bus as a queue technology, but we could easily change it AWS SQS, Rabbit MQ , or any other platform that DAPR supports without having to make any changes to application code

A lot of organizations are using ServiceNow to manage requests for creating new compute resources in the could ( i.e servers, lambda functions, containers …)

Usually, CMP tools like Scalr, or even ServiceNow Cloud Management can ( to a certain degree ) automate this process, but there are two major issues with these approaches :

1 – For these tools to be used properly they need lengthy customization to fit the business architecture of the organization, mapping all the business units, integrating with existing tools …

2 – It can be expensive, the price per node model can add up quickly for companies with a large number of servers deployed.

This a way to automate server build by using ServerNow Orchestration Module, and Serverless to build the integration.

Creating ServiceNow Form

 

 

ServiceNow workflow

to simplify the process I’ve only used a simple RunScript Step, other activities can be added like CMDB integration, approvals, notifications, etc …

here is a look at what the script does :

• Gets all the parameters from the form
• make an API call to API Gateway and Lambda
• Lambda will trigger

[code]

var os = current.variables.os;
var inst_size = current.variables.inst_size;

var request = new sn_ws.RESTMessageV2();
request.setEndpoint(‘https://9drnhpoorj.execute-api.us-east-1.amazonaws.com/dev/instance’);
request.setBasicAuth(“apikey1″,”mutKJWAolpsdfsdflksd8ndew02234LNFQQvq”);
request.setHttpMethod(‘POST’);
request.setRequestHeader(“Accept”, “application/json”);
request.setRequestHeader(‘Content-Type’, ‘application/json’);

request.setStringParameterNoEscape(‘os’,current.variables.os);
request.setStringParameterNoEscape(‘inst_size’,current.variables.inst_size);
request.setStringParameterNoEscape(‘volume_size’,current.variables.volume_size1);

request.setRequestHeader(‘Content-Type’, ‘application/json’);
request.setRequestBody(‘{“os”:”${os}”,”inst_size”:”${inst_size}”}’);
var response = request.execute();

[/code]

 

The AWS side

To build things on the AWS side, I used Serverless,

check out the code at the github repo

Demo

if I request an EC2 instance that’s an m1.small running an amazon linux OS

if I take a look at the AWS console I can see that the server is getting created  :

With the right parameters :

 

Minio is a local cloud object storage server, it’s open source, released under Apache License V2.0, allowing developers and devops to have a local and a public cloud storage to:

• backup VMs
• backup containers
• store unstructured Data ( photos, files, …)
• store objects in AWS S3
• store objects using SDKs (GO, Javascripts, Java )

to start a server you can use the container image of MiniO available on Docker hub here :

mini0/minio

you can run this cmd :

docker pull minio/minio

to start the server run :

 docker run -p 9000:9000 minio/minio server /export

you can access the web UI at http://localhost:9000

the access key and secret key for the local server are generated at the start of the server

create a bucket :

accessible also through the web UI:

using your AWS S3 storage :

we need to add AWS S3 end point to the list of hosts :

mc config host add my-aws https://s3.amazonaws.com YOUR_ACCESS_KEY  YOUR_SECRET_KEY

create a bucket in S3 :

and it’s created  :

 

I have been browsing the internet for blogs or articles to help Chef developers have a way of promoting the code of their cookbooks, a way of vetting code, and avoiding that code goes from Operations guys straight to production.

I have found a lot of theoretical articles on building a CI pipeline for chef cookbooks, but not a lot of practical ones,  so I decided to make a proof of concept for  the public and my team as well.

when it comes to integration tools, I like Jenkins, it’s open source and the community is very active in adding  and updating plugins .

In this example I will use a Java cookbook as a code base, and I will be running 4 test :

• Foodcritic : a helpful lint tool you can use to check your Chef cookbooks for common problems. It comes with 61 built-in rules that identify problems ranging from simple style inconsistencies to difficult to diagnose issues that will hurt in production.
• ChefSpec : a unit testing framework for testing Chef cookbooks. ChefSpec makes it easy to write examples and get fast feedback on cookbook changes without the need for virtual machines or cloud servers.
• Rubocop :  a Ruby static code analyzer. Out of the box it will enforce many of the guidelines outlined in the community Ruby Style Guide.
• Test Kitchen : a test harness tool to execute your configured code on one or more platforms in isolation. A driver plugin architecture is used which lets you run your code on various cloud providers and virtualization technologies such as Amazon EC2,  Vagrant, Docker, LXC containers, and more. Many testing frameworks are already supported out of the box including Bats, shUnit2, RSpec, Serverspec, with others being created weekly.

of course you can have all these tools in one package…. the famous ChefDK

Code Promotion :

The concept of code promotion helps the CI process distinguish between good and bad builds, I like to define a good build as a build where ALL the tests are successful .

Jenkins helps you implement this concept with a community plugin : Promoted Build Plugin

based of the status of your build ( promoted of not)  you can control the code that goes into your repository (github or gitlab), you can use set up hooks to deny merge requests from builds that are not promoted.

Jobs:

let’s setup our jobs, we will too categories of jobs :

• Build Jobs
• Test Jobs

 

whenever a build job is successful will trigger all the test jobs to start.

Build-java-cookbook : will clone the code repo and create a temporary artifact, this is the config section for this job

Rubocop Test : will copy the temporary artifact decompress it to have all code repo and run rubocop test on the code :

ChefSpec Test :

FoodCritic : 

Test Kitchen : 

Test Kitchen will spin a vagrant box (ubuntu-14.04) and run the cookbook on it and test the results.

First Run : 

with the configurations above we run the build and test jobs :

Result :

Rubocop test failed, by looking at the execution log we can see why :

+ rubocop
Inspecting 44 files
.......CC...CC........C..C..................

Offenses:

providers/alternatives.rb:34:38: C: Use shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path} | grep 'priority #{priority}$'").exitstatus.zero? instead of shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path} | grep 'priority #{priority}$'").exitstatus == 0.
      alternative_exists_same_prio = shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path} | grep 'priority #{priority}$'").exitstatus == 0
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:35:28: C: Use shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path}").exitstatus.zero? instead of shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path}").exitstatus == 0.
      alternative_exists = shell_out("#{alternatives_cmd} --display #{cmd} | grep #{alt_path}").exitstatus == 0
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:43:18: C: Use remove_cmd.exitstatus.zero? instead of remove_cmd.exitstatus == 0.
          unless remove_cmd.exitstatus == 0
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:57:18: C: Use install_cmd.exitstatus.zero? instead of install_cmd.exitstatus == 0.
          unless install_cmd.exitstatus == 0
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:66:28: C: Use shell_out("#{alternatives_cmd} --display #{cmd} | grep \"link currently points to #{alt_path}\"").exitstatus.zero? instead of shell_out("#{alternatives_cmd} --display #{cmd} | grep \"link currently points to #{alt_path}\"").exitstatus == 0.
      alternative_is_set = shell_out("#{alternatives_cmd} --display #{cmd} | grep \"link currently points to #{alt_path}\"").exitstatus == 0
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:72:16: C: Use set_cmd.exitstatus.zero? instead of set_cmd.exitstatus == 0.
        unless set_cmd.exitstatus == 0
               ^^^^^^^^^^^^^^^^^^^^^^^
providers/alternatives.rb:87:50: C: Use cmd.exitstatus.zero? instead of cmd.exitstatus == 0.
    new_resource.updated_by_last_action(true) if cmd.exitstatus == 0
                                                 ^^^^^^^^^^^^^^^^^^^
providers/ark.rb:39:20: C: Omit parentheses for ternary conditions.
    package_name = (file_name =~ /^server-jre.*$/) ? 'jdk' : file_name.scan(/[a-z]+/)[0]
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
providers/ark.rb:134:14: C: Use 0o for octal literals.
        mode 0755
             ^^^^
providers/ark.rb:149:14: C: Closing method call brace must be on the line after the last argument when opening brace is on a separate line from the first argument.
            ))
             ^
providers/ark.rb:150:16: C: Use cmd.exitstatus.zero? instead of cmd.exitstatus == 0.
        unless cmd.exitstatus == 0
               ^^^^^^^^^^^^^^^^^^^
providers/ark.rb:157:16: C: Use cmd.exitstatus.zero? instead of cmd.exitstatus == 0.
        unless cmd.exitstatus == 0
               ^^^^^^^^^^^^^^^^^^^
providers/ark.rb:164:16: C: Use cmd.exitstatus.zero? instead of cmd.exitstatus == 0.
        unless cmd.exitstatus == 0
               ^^^^^^^^^^^^^^^^^^^
providers/ark.rb:172:14: C: Use cmd.exitstatus.zero? instead of cmd.exitstatus == 0.
      unless cmd.exitstatus == 0
             ^^^^^^^^^^^^^^^^^^^
recipes/ibm.rb:44:8: C: Use 0o for octal literals.
  mode 00755
       ^^^^^
recipes/ibm_tar.rb:36:8: C: Use 0o for octal literals.
  mode 00755
       ^^^^^
recipes/ibm_tar.rb:49:8: C: Use 0o for octal literals.
  mode 00755
       ^^^^^
recipes/set_java_home.rb:27:8: C: Use 0o for octal literals.
  mode 00755
       ^^^^^
recipes/set_java_home.rb:32:8: C: Use 0o for octal literals.
  mode 00755
       ^^^^^
resources/ark.rb:39:54: C: Use 0o for octal literals.
attribute :app_home_mode, kind_of: Integer, default: 0755
                                                     ^^^^

44 files inspected, 20 offenses detected
Build step 'Execute shell' marked build as failure
Finished: FAILURE

 

 

let’s go ahead and fix these offenses and commit the code :

we restart the build :

and here everything is green this time :

from this point on you can create do two things :

• save your cookbook in a private supermarket with a corresponding version number
• upload this cookbook to chef server

 

Promotion status :

After the completion of all tests, this build can now be promoted.

 

 

until today I knew that running containers was always dependent on the existence of a host and an OS of some kind, but I came across this project : vSphere Integrated containers, it’s a runtime environment allowing developer to run containers as VMs, instead of running containers in  VMs .

there is a good read to understand the contrast between traditional containers and containerVMs

untar the compressed file :

$ tar xvzf vic_3711.tar.gz

you can use vSphere or ESXI web client to take a look :

creating ContainerVM :

$ docker –tls run  –name container1 ubuntu

the container has been created :

 

Conclusion :

ContainerVMs seem to have the following distinctive characteristics over the traditional containers  :

1. There is no default shared filesystem between the container and its host
   • Volumes are attached to the container as disks and are completely isolated from each other
   • A shared filesystem could be provided by something like an NFS volume driver
2. The way that you do low-level management and monitoring of a container is different. There is no VCH shell.
   • Any API-level control plane query, such as docker ps, works as expected
   • Low-level management and monitoring uses exactly the same tools and processes as for a VM
3. The kernel running in the container is not shared with any other container
   • This means that there is no such thing as an optional privileged mode. Every container is privileged and fully isolated.
   • When a containerVM kernel is forked rather than booted, much of its immutable memory is shared with a parenttemplate
4. There is no such thing as unspecified memory or CPU limits
   • A Linux container will have access to all of the CPU and memory resource available in its host if not specified
   • A containerVM must have memory and CPU limits defined, either derived from a default or specified explicitly

but the traditional containers like Docker are definitely  a more mature solution, offers more tools for orchestration and scaling.

Riak is some hot stuff lately with the increasing need for clusterzitation in the world of NoSQL data stores .

Riak is a solution to big data problem, it was based on Amazon Dynamo design, to respond to request at a very large scale,

Basho introduced Riak as fault tolerant, simple, scalable, high availability friendly .

it’s fairly easy to create/add nodes with riak-admin to a riak cluster, but if this is combined with docker-compose capabilities it will give you the possibility to have an easily deployable/scalable cluster of riak nodes.

I created a docker-compose yaml to specify all the components of the cluster, basically a seed and a set of nodes

I used  Hectcastro Riak docker image, because :  that’s the beauty of containers, they are reusable !

• install docker-engine and docker compose
• You can either, copy/past the content of those files or clone this repo :

$git clone https://github.com/mbenachour/riak-cluster-compose.git

$cd riak-cluster-compose

 

• start compose as a daemon :

$docker-compose up -d

• you will have one seed and one node running :

• list all running containers

• let’s create an “Artists” buckets and add an object using node1 (port : 32812)

$curl -i -d '{"name":"Bruce"}' -H "Content-Type: application/json" \
localhost:32812/riak/artists/Bruce

• check the bucket was created :

Scale time ! : 

• to scale you cluster you can add 3 nodes

  $docker scale riak_node=4

•  let’s query node4 for the list of buckets (port: 32818)

works !

if you are more interested to scale on multiple hosts, you can combine this with docker swarm.