sdk

README

Build, run, and manage code-first composites on Kubernetes.

• For in-depth information about how to use Cellery, visit https://wso2-cellery.github.io/.
• Engage with our community via,
  • Slack
  • Twitter
  • Cellery-dev mailing list
  • Bi-weekly community call on Wednesdays at 9:00 AM PDT/9:30 PM IST (Staring from November 6th). Subcribe to cellery community calendar to know get notified about our events. 
• To learn how to participate in our overall community, visit our community page.
• To understand the usecases and integrations of Cellery, visit our blogs.
• To explore already existing Cellery images, visit cellery hub.

In this README:

• Introduction
• Why Cellery?
• Quickstart guide
• What's next?

In addition, here are some other documents you may wish to read:

• Cell Based Architecture - explains the concepts of Cell based Architecture.
• Cellery Architecture - explains the high-level architecture of Cellery.
• How to code cells? - explains how Cellery cells are written.
• CLI commands - reference for CLI commands.
• Samples - a collection of useful samples.
• Kubernetes Resources Overview - explains Kubernetes resources used by the Cellery.
• Blogs - a collection of useful integration and user stories.
• Cellery community - describes how to get involved and contribute to the Cellery project.
• Cellery roadmap - provides the roadmap of the Cellery project.

Introduction

Cellery is a code-first approach to building, integrating, running and managing composite microservice applications on Kubernetes. Build, push/pull, run, scale and observe composites. Create secure APIs by default, code components in any language.

---

Why Cellery?

The use of microservices and/or serverless functions is exploding as organisations aim to get better agility and speed of development. This quickly gets out of control, resulting in tens or hundreds of microservices in a highly connected network. There is a strong need for an approach that helps create higher-level constructs from multiple microservices and serverless functions. Cellery aims to create composites with well-defined boundaries that fit with CI/CD pipelines and modern development and DevOps practices. You can read more about this approach here

Cellery provides a developer tooling, runtime and a management plane. This allows you to develop, run and manage your composite microservice applications on Kubernetes.

• Cellery SDK

  The SDK allows developers to write, build, run & manage cells. A cell description file is written using the Ballerina programming language. In a nutshell, this file declares the microservice components that have to be included in the cell, the relationship between those components, dependencies to other cells, and it also declares the API that need to be exposed.

  A CLI is also part of this SDK, which allows you to build, run, test and manage your cells.

• Cellery Mesh

  The mesh provides the wiring & communications medium between cells. Components in a cell cannot invoke components in other cells directly. Only APIs exposed by the cells are invokable. These interactions are strictly governed by security policies.

• Cellery Management

  This consists of a management plane, which allows you to observe your cells in the runtime, as well as other runtime aspects, and it also allows you to manage security and other policies.

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Quickstart Guide

The easiest way to setup Cellery is using the 'local' mode which creates Cellery runtime on Minikube.

Kindly note that if you freshly installed minikube, you would have to execute minikube start, create a temporary cluster and remove it. This is due to a known issue in minikube (https://github.com/kubernetes/minikube/issues/5716).

For other installation approaches including GCP and Docker for Desktop see here

Prerequisites

• Minikube
• Kubectl version 1.13/1.14/1.15

Download Cellery

Linux

Download the 0.6.0 Cellery(.deb) installer and install it using dpkg command as shown below.

dpkg -i cellery-ubuntu-x64-<version>.deb

Mac OS

• Download 0.6.0 Cellery(.pkg) installer and install it by following macOS package installation steps.

• Cellery is avaialbe as a Brew Cask. Run below to install through Brew

  brew cask install cellery
  

Setup Cellery runtime

Once Cellery has been installed, verify the installation is working by executing cellery version.

In this quickstart guide, we will install a basic local Cellery runtime by running the following command:

1. Run the local setup command.

   cellery setup create local -y
   

   This may take a few minutes. If the setup was successful, you should see the following message:

   ✔ Runtime status (Cellery)...OK
   

2. Once the setup completes, run the following command to check the status:

   cellery list instances
   

   You shouldn't see any errors.

Now that we have installed Cellery let's validate that it is running using a simple cell.

Hello world with Cellery

Let's quickly run a sample hello world cell as shown in the diagram below.

The hello-world-cell contains one component hello. The hello component is defined by a container image which is written in Node.js and it is a simple webapp. In the quick start we will be deploying the hello-world-cell.

Now let's look at the steps required to run this cell.

1. Execute the cellery run command that will download the hello-world cell from the wso2cellery organization in cellery hub and run the cell.

   $ cellery run wso2cellery/hello-world-cell:0.6.0 -n hello-world-cell
   

   You should see the following output:

   ✔ Connecting to registry.hub.cellery.io
   ✔ Fetching metadata
   ✔ Pulling image wso2cellery/hello-world-cell:0.6.0
   ✔ Saving new Image to the Local Repository
   
   Image Digest : sha256:2d5659e5787df7e7ae0f58671c0b9d857b5a19e5fbdb02fccbc98a64016a97f6
   
   ✔ Extracting Cell Image wso2cellery/hello-world-cell:0.6.0
   ✔ Reading Image wso2cellery/hello-world-cell:0.6.0
   Info: Main Instance: hello-world-cell
   Info: Validating dependencies
   Info: Instances to be Used
   ------------------------------------------------------------------------------------------------------------------------
   INSTANCE NAME                  CELL IMAGE                          USED INSTANCE             KIND            SHARED
   ------------------------------------------------------------------------------------------------------------------------
   hello-world-cell               wso2cellery/hello-world-cell:0.6.0 To be Created             Cell            -
   ------------------------------------------------------------------------------------------------------------------------
   Info: Dependency Tree to be Used
   
   No Dependencies
   ✔ Starting main instance hello-world-cell
   
   
   ✔ Successfully deployed cell image: wso2cellery/hello-world-cell:0.6.0
   
   What's next?
   --------------------------------------------------------
   Execute the following command to list running cells:
     $ cellery list instances
   --------------------------------------------------------
   

   Please allow a few minutes for completion.

2. Execute cellery list instances to check the status of your cell.

   $ cellery list instances
            INSTANCE        CELL IMAGE                           STATUS        GATEWAY               COMPONENTS          AGE
    ---------------------- ------------------------------------ -------- -------------------------- ------------ -----------------------
     hello-world            wso2cellery/hello-world-cell:0.6.0   Ready    hello--gateway-service        1          30 minutes 48 seconds
   

3. Execute the following command and get the minikube ip address of cellery-local-setup

     minikube ip --profile cellery-local-setup
   

   Add the following line to the /etc/hosts file.

     <MINIKUBE_IP> hello-world.com
   

   Note: The above provided value host entry is for Cellery local setup. If you are using a Cellery on,

   • Existing kubernetes cluster (e.g.: Docker for Mac, Kubeadm, Minikube, etc) - Configure the host entry as explained here.
   • GCP - Configure the host entry as explained /etc/hosts as mentioned here.

4. Now browse to http://hello-world.com/ and you should see the web page.

   Congratulations! You have successfully got your first cell running!

5. Finally, terminate the cell instance that you started using the cellery terminate command.

   $ cellery terminate hello-world-cell
   

---

What's next?

• Installation Options - lists all installation options with Cellery.
• Samples - a collection of useful samples.
• CLI commands - reference for CLI commands.

Learn about full lifecycle of cells in Cellery from,

• Developing and running a Cell - step by step explanation on how you could define your own cells.
• Developing & running a cell with resources and/or tests - Step by step explanation on how you could define a cell with resources and/or tests
• Testing a Cell - provides the instructions to run test against cells.
• Managing a Cell - lists the management aspects of cells in the runtime.
  • Patch - patch a running cell instance.
  • Scale up/down - scalability of running cell instances with zero scaling and horizontal autoscaler.
  • Observability - provides the runtime insight of cells and components.