High Availability Setup

This tutorial will demonstrate that the Context Management API's can easily be deployed in a 'High Availability', setup that can provide added redundancy and higher performance. It will be a demonstration using Docker Swarm technology, and only focus on the Context Management API's and not the underlying database. Deploying a MongoDB is out of scope of this guide, but managed MogoDB instances can be used with this tutorial, or can be configured by following tutorials online e.g. medium.com or cloud.mongodb.com.

Docker Swarm

Setting up nodes in a Docker Swarm cluster is beyond the scope of this tutorial, but the docker website has excellent tutorials on this. It is assumed that you have access to a docker swarm master node, and this can be tested by issuing the following command on your cluster.

docker node ls

it you are on a Swarm Master node a health cluster could look like this:

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
zuf5x23otp4y2jjciughyh025     hyper038            Ready               Active                                  19.03.5
auouuclvmpzt7ra7s7pv31doi     hyper039            Ready               Active                                  19.03.5
4xuji4cr0hx2nhea1v1zthozc     hyper040            Ready               Active                                  19.03.1
nnfaglnwudp4kt9gq5d96rgvl *   swarm-master        Ready               Active              Leader              19.03.1

If you encounter an error such as the following:

Error response from daemon: This node is not a swarm manager. Worker nodes cant be used to view or modify cluster state. Please run this command on a manager node or promote the current node to a manager.

then you need to follow up wit the documentation for setting up a Docker Swarm Cluster.

MongoDB Prerequisites

The Orion Context Broker requires a MongoDB database to run, and for this tutorial we are using a cloud hosted MongoDB instance.

Please note. The Orion Context Broker used in this tutorial DOES NOT support version 4.0 or above. It is possible to instantiate a MongoDB 3.6.15 on the cloud.mongodb.com site, and it will be used throughout this tutorial.

Please Note. The connection string must comply to the old MongoDB 3.4 standard due to the legacy version of C++ drivers used by the Orion Context Broker.

You can test your connection string using this example in a terminal window where the mongo-cli is installed, just replace URI, username and password with values matching your setup.

mongo "mongodb://cluster0-shard-00-00-60238.mongodb.net:27017,cluster0-shard-00-01-60238.mongodb.net:27017,cluster0-shard-00-02-60238.mongodb.net:27017/test?replicaSet=Cluster0-shard-0" --ssl --authenticationDatabase admin --username <username> --password <password>

Service Definition

Deploying the Orion Context Broker is extremely simple, as it is simply a binary that runs while connected to a MongoDB. To start a service with one replica, the following command could be issued:

docker service create --replicas 1 --name orion-cb   --publish 1026:1026 --entrypoint "/usr/bin/contextBroker" fiware/orion:2.3.0 -fg -dbhost cluster0-shard-00-00-60238.mongodb.net:27017,cluster0-shard-00-01-60238.mongodb.net:27017,cluster0-shard-00-02-60238.mongodb.net:27017 -rplSet Cluster0-shard-0 -dbuser <username> -dbpwd <password> -dbAuthDb admin -dbSSL -db test

It is now easy to scale the orion-cb service to run multiple instances against the MongoDB cluster:

docker service scale orion-cb=3

To check the services converge, issue the command below.

docker service ps orion-cb

The output should look like this:

ID                  NAME                IMAGE                NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
fx1d7s3nd88g        orion-cb.1          fiware/orion:2.3.0   swarm-master        Running             Running 4 minutes ago
y73zogam7ora        orion-cb.2          fiware/orion:2.3.0   hyper038            Running             Running 11 seconds ago
1s8ylotu37va        orion-cb.3          fiware/orion:2.3.0   hyper039            Running             Running 11 seconds ago

Disclaimer

This is an example to demonstrate that the Orion Context Broker can run in a 'High Availability' setup. Actual deployment in a production environment should as always be carefully considered. Both Docker Swarm and Kubernetes are viable solutions, here we have focused on demonstrating Docker Swarm.