69 lines
1.4 KiB
Markdown
69 lines
1.4 KiB
Markdown
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## Docker Swarm health check example
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This example shows how health check works in Docker Swarm.
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### What does this container do?
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Container runs a nginx server and it also runs a script which writes a ``dead``
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status to ``/usr/share/nginx/html/status`` file on every odd run which is then
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picked by the health check that expects ``alive`` status from the nginx running
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in the container.
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So every odd run the container gets ``unhealthy`` status.
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Then you can observe that running this container in Docker Engine alone will
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not restart it. Hence we will run it as a service in the Docker Swarm which
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will ensure the container gets restarted until it gets ``healthy`` status.
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### Building image
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```
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docker build -t healthcheck-test .
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```
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### Setting up env
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Make sure you have recent Docker Engine installed.
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```
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docker swarm init
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```
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### Running the service
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```
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docker service create \
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--name test1 \
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--mount type=bind,src=/tmp,dst=/usr/share/nginx/html \
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--detach healtcheck-test
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```
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### Watching the healtcheck
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```
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docker ps |grep test1
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docker service ls
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```
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### Cleaning up
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```
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docker service rm test1
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docker swarm leave --force
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rm -rf -- /tmp/html
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```
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### Extra
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If you want to restart the container manually, you need to downscale it to 0
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first and then upscale it back again.
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```
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docker service scale test1=0
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docker service scale test1=1
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```
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### References
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- https://docs.docker.com/compose/compose-file/
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- https://docs.docker.com/engine/reference/builder/
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