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Docker healthcheck document shows this for curl:
HEALTHCHECK --interval=5m --timeout=3s \
CMD curl -f http://localhost/ || exit 1
I want a one-line equivalent in wget that would exit 1 when HTTP 200 is not returned.
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We can also see the health status by running docker ps. Notice under STATUS, the status is Up with (healthy) next to it. The health status appears only when a health check is configured.
If a health check fails but the subsequent one passes, the container will not transition to unhealthy . It will become unhealthy after three consecutive failed checks. --timeout – Set the timeout for health check commands. Docker will treat the check as failed if the command doesn't exit within this time frame.
Docker Swarm is a clustering and scheduling tool for Docker containers. With Swarm, IT administrators and developers can establish and manage a cluster of Docker nodes as a single virtual system. Swarm mode also exists natively for Docker Engine, the layer between the OS and container images.
2. Docker Compose depends_on. depends_on is a Docker Compose keyword to set the order in which services must start and stop. For example, suppose we want our web application, which we'll build as a web-app image, to start after our Postgres container.
The following seems to be the equivalent:
HEALTHCHECK --interval=5m --timeout=3s \
CMD wget --no-verbose --tries=1 --spider http://localhost/ || exit 1
Dennis Hoer's answer is great, but I prefer -nv (--no-verbose) instead of --quiet, then if an error occurs, the reason is available from Docker:
HEALTHCHECK --interval=5s --timeout=5s --retries=3 \
CMD wget -nv -t1 --spider 'http://localhost:8000/' || exit 1
Example output captured by Docker:
% docker inspect $container --format "{{ (index (.State.Health.Log) 0).Output }}"
Connecting to localhost:8000 (127.0.0.1:8000)
wget: server returned error: HTTP/1.1 404 Not Found
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