Show HN: Is_ready – Wait for many services to become available

Re:Show HN: Is_ready – Wait for many services to become avai... by tommasoamici on Sunday April 28, 2024 @06:55AM (#40187625)

>Feels like something very similar should be built into tools like docker-compose.

In docker compose you can use `depends_on` [0] to define dependencies between containers and by default it will wait until a dependent container is "ready".

But you can also use a more verbose syntax to wait until a container is "healthy", as defined by its own healthcheck.

    services:
      web:
        depends_on:
          db:
            condition: service_healthy
      db:
        image: postgres

[0] https://docs.docker.com/compose/compose-file/05-services/#de...

[ Parent | on HN ]

Re:Show HN: Is_ready – Wait for many services to become avai... by stavepan on Sunday April 28, 2024 @08:15AM (#40188040)

That's true.

For example, in the case of PostgreSQL, there is already a tool called pg_isready [0] to do this inside a healthcheck as you described.

services: postgres-db: image: postgres healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"]

  application:
    image: image
    depends_on:
      postgres-db:
        condition: service_healthy

However, this is not the case for other databases/services.

[0] https://www.postgresql.org/docs/current/app-pg-isready.html

[ Parent | on HN ]