How do you do a Healthcheck for Fluentd's Default ports?

Question

I was looking through docker hub, etc and generally I can find a mechanism to look up healthchecks for different containers. I didnt see any for FluentD though.

I would like to essentially do a curl from the container to confirm it is healthy.

My issue is that i have underlying containers which will start immediately but fail because 24224 on fluentd is not available.

So what I thought to do was to write similar to:

version: "3.3"
services:
  fluentd:
    ports:
      - "24224:24224"
      - "24224:24224/udp"
    healthcheck:
      test: curl --fail -s http://localhost:24224 || exit 1
      interval: 30s
      timeout: 30s
      retries: 5
      start_period: 30s
  sample:
    depends_on:
      fluentd:
        condition: container_healthy

In this sample test, It seems that the Curl command I set up was not the correct command to validate the health of fluentd.

I did not seem to find anything specific to this from my searches, but maybe others might know what to do.

My error was: Error response from daemon: failed to initialize logging driver: dial tcp [::1]:24224: connect: connection refused when it attempts to set up logging to fluentd.

Answer 1

I made it work through using netcat but it requires a custom Dockerfile for installing netcat:

FROM fluent/fluentd:v1.17-debian-1

USER root
RUN apt-get update && \
    apt-get install -y build-essential libpq-dev curl netcat-openbsd && \
    fluent-gem install fluent-plugin-postgres && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

USER fluent
ENTRYPOINT ["tini",  "--", "/bin/entrypoint.sh"]
CMD ["fluentd"]

Compose configuration:

  fluentd:
    build:
      context: .
      dockerfile: fluentd.Dockerfile
    container_name: fluentd
    volumes:
      - ./fluentd.conf:/fluentd/etc/fluentd.conf
    ports:
      - "24224:24224"
      - "24224:24224/udp"
    healthcheck:
      test: ["CMD", "nc", "-z", "localhost", "24224"]
      interval: 10s
      timeout: 5s
      retries: 3