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vagrant @ ubuntu: ~ $ sudo docker run -d –restart = on-failure: 3 ubuntu sleep 10

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vagrant @ ubuntu: ~ $ sleep 10

vagrant @ ubuntu: ~ $ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

c3bc2d2e37a6 ubuntu "sleep 10" 9 minutes ago Up 2 seconds keen_sinoussi

vagrant @ ubuntu: ~ $ sleep 10

vagrant @ ubuntu: ~ $ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

c3bc2d2e37a6 ubuntu "sleep 10" 10 minutes ago Up 9 seconds keen_sinoussi

vagrant @ ubuntu: ~ $ sleep 10

vagrant @ ubuntu: ~ $ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

c3bc2d2e37a6 ubuntu "sleep 10" 10 minutes ago Up 2 seconds keen_sinoussi

Another aspect is when to consider the container dead. By default, this is a process crash. But, by far, the application does not always crash itself in case of an error in order to allow the container to be restarted. For example, a server may be designed incorrectly and try to download the necessary libraries during its startup, but it does not have this opportunity, for example, due to the blocking of requests by the firewall. In such a scenario, the server can wait a long time if an adequate timeout is not specified. In this case, we need to check the functionality. For a web server, this is a response to a specific url, for example:

docker run –rm -d \

–-name = elasticsearch \

–-health-cmd = "curl –silent –fail localhost: 9200 / _cluster / health || exit 1" \

–-health-interval = 5s \

–-health-retries = 12 \

–-health-timeout = 20s \

{image}

For demonstration, we will use the file creation command. If the application has not reached the working state within the allotted time limit (set to 0) (for example, creating a file), then it is marked as working, but before that the specified number of checks is done:

vagrant @ ubuntu: ~ $ sudo docker run \

–d –name healt \

–-health-timeout = 0s \

–-health-interval = 5s \

–-health-retries = 3 \

–-health-cmd = "ls / halth" \

ubuntu bash -c 'sleep 1000'

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vagrant @ ubuntu: ~ $ sudo docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

c0041a8d973e ubuntu "bash -c 'sleep 1000'" 4 seconds ago Up 3 seconds (health: starting) healt

vagrant @ ubuntu: ~ $ sleep 20

vagrant @ ubuntu: ~ $ sudo docker ps