td-cluster

Truedat Cluster modules. Provides modules for managing elixir nodes with microservices approach

Configuration

Files

config/runtime.exs

config :td_cluster,
  scope: :truedat,
  topologies: [
    truedat: [
      strategy: TdCluster.Strategy,
      config: [
        node_template: System.get_env("RELEASE_NODE_TEMPLATE", "{{service}}@{{hostname}}"),
        services: [
          :dd,
          :qx
        ],
        groups: [:dd],
        polling_interval: 5_000
      ]
    ]
  ]

td_cluster/scope:

The scope of the process group to which you want your node to belong. This configuration is in accordance with the following documentation. You can replace :truedat for another scope

td_cluster/topologies/truedat/config

• node_template: It is a text string with the template that forms the node names in the cluster
• services: Services you want to connect with
• groups: Process groups you want your node to belong to
• polling_interval: The frequency with which connection attempts will be retried for nodes that are not connected, expressed in milliseconds

application.ex

children = [
  # ...
  TdCluster.Supervisor,
]

env.sh.eex

#!/bin/sh

# RELEASE_NODE MUST BE DEFINED IN EXECUTION ENVIRONMENT

if [ -n "$RELEASE_NODE" ]; then
  DEFAULT_NAME=<%= @release.name %>
  export RELEASE_DISTRIBUTION=name
fi
...

Environment Variables

• RELEASE_NODE_TEMPLATE: It is a text string with the template that forms the node names in the cluster. It can have the following wildcards that will be replaced by the corresponding values:

  • service: Service name of the node
  • hostname: Hostname of machine that will execute the node

  The wildcards will be enclosed in {{service}}

  Examples:

  For local:

  • service: dd
  • hostname: MYHOSTNAME
  • RELEASE_NODE_TEMPLATE: "{{service}}@{{hostname}}"

  My node name will be dd@MYHOSTNAME

  For kubernetes:

  • service: dd
  • RELEASE_NODE_TEMPLATE: "truedat@{{service}}.default.svc.cluster.local"

  My node name will be [email protected]

Mock ClusterHandler for testing

You can set up an implementation module for TdCluster.ClusterHandler. This module should be defined with the behaviour TdCluster.ClusterHandlerBehaviour and can be set as the attribute :cluster_handler in the :td_cluster configuration. This allows us to create a mock using Mox that implements that behaviour and use it to replace TdCluster.ClusterHandler at runtime.

To create the Mock for TdCluster.ClusterHandler, the following files need to be configured:

Install Mox adding this deps to mix.exs

mix.exs

# ...
defp deps do
  [
    # ...
    {:mox, "~> 1.0", only: :test},
  ]
end

Import Mox for all test cases

test/support/conn_case.ex

# ...
using do
  quote do
    # ...
    import Mox
    # ...
  end
end

Create Mock of ClusterHandler using TdCluster.ClusterHandlerBehaviour

test/test_helper.exs

# ...
ExUnit.start()
Mox.defmock(MockClusterHandler, for: TdCluster.ClusterHandlerBehaviour)
# ...

Replace TdCluster.ClusterHandler implementation by MockClusterHandler

config/test.exs

# ...
config :td_cluster, :cluster_handler, MockClusterHandler
# ...

You can use the following line in your tests to replace the result of the call to the call function of TdCluster.HandleCluster with a predefined value:

expect(
  MockClusterHandler,
  :call,
  fn _service, _module, _func, _args -> {:ok, data_structures} end
)

Running the tests

Run all aplication tests with mix test.