Canton and Docker Compose health checks

Tutorials and Guides
1

Background

On a recent project, I needed to run a Docker Compose network.
However, I needed one of the containers to wait and not start
until the other containers were up-and-running.

The Problem

In this example, I need a utils container to run after participant1 and participant2 are up-and-running. Otherwise, the result is one of these errors, depending on the race conditions:

Node participant1 is not initialized and
therefore does not have an Id assigned yet.

java.lang.IndexOutOfBoundsException:
1 is out of bounds (min 0, max 0)

The Solution

  1. Turn on the gRPC Health Service on the Canton nodes. For example:
canton {
  participants {
    participant1 {
           :
           :
      monitoring.grpc-health-server {
        address = participant1
        port = 5861
      }
    }
  }
}
  1. Add a Docker Compose healthcheck for the containers. For example:
services:
  participant1:
        :
        :
    healthcheck:
      test:
        [
          "CMD",
          "/usr/local/bin/grpc_health_probe",
          "--addr",
          "participant1:5861"
        ]
  1. Add a Docker Compose condition to the dependent container. For example:
services:
  utils:
     :
     :
    depends_on:
      participant1:
        condition: service_healthy
      participant2:
        condition: service_healthy

Sample Outputs

Before

> docker compose up

[+] Running 5/5
 ✔ Network daml-public-demos_default  Created
 ✔ Container mydomain                 Created
 ✔ Container participant2             Created
 ✔ Container participant1             Created
 ✔ Container utils                    Created
Attaching to utils
utils  | ERROR Node participant1 is not initialized
         and therefore does not have an Id assigned yet.

After

> docker compose up

[+] Running 5/4
 ✔ Network daml-public-demos_default  Created
 ✔ Container mydomain                 Created
 ✔ Container participant2             Created
 ✔ Container participant1             Created
 ✔ Container utils                    Created
Attaching to utils
utils  | alice::12202df...
utils  | bob::12209f3...

Source Code

The demo source code is available here.

References

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