docker swarm find hostname by container id or hostname using two methods

docker-swarm-find-container

#!/bin/bash

#
# Default settings block, change here if you need or put other defaults to your .bashrc
#

DSFC_USER="${DSFC_USER:-root}" # defaults to root
DSFC_HOSTS_GREP="${DSFC_HOSTS_GREP:-"swarm-"}" # what to grep in /etc/hosts
DSFC_HOSTS_LIST="${DSFC_HOSTS_LIST:-`(cat /etc/hosts | grep ${DSFC_HOSTS_GREP} | cut -f1 | xargs -L1 echo | uniq)`}" # change the default inside backticks to your way to get hosts list
DSFC_METHOD_SSH="${DSFC_METHOD_SSH:-1}" # whether to use the ssh and docker ps method
DSFC_METHOD_SSH_CONNECT_TIMEOUT="${DSFC_METHOD_SSH_CONNECT_TIMEOUT:-5}" # connection timeout for the ssh method
DSFC_METHOD_DSM="${DSFC_METHOD_DSM:-1}" # whether to fallback to the local docker swarm manager capabilities
DSCF_METHOD_DSM_SERVICE="${DSCF_METHOD_DSM_SERVICE:-.}" # sets a grep pattern for service name too look the container among - speeds up docker swarm manager method.

#
# Usage printing block
#

read -r -d '' usage << EOM
Finds container by id on a predefined hosts list, since swarm does not make it easy. Assuming you have ssh access to the swarm nodes list or running on a manager node.

   Usage:
        $(basename "$0") [-h|--help] - this message
        $(basename "$0") CONTAINER_ID_OR_NAME [SERVICE_NAME] - this is basically strings passed to grep on each host. Set SERVICE_NAME if known to speed up search in Docker Swarm Manager node mode.

   Environment variables:
   		DSFC_HOSTS_LIST=see-explanation
   			list of hosts to connect to for the "ssh docker ps" method. Defaults to all records from "/etc/hosts" having substring defined in DSFC_HOSTS_GREP.
   		DSFC_HOSTS_GREP=swarm-
   			if DSFC_HOSTS_LIST is not set, this variable will be used as the grep pattern to filter hosts from "/etc/hosts"
   		DSFC_USER=root
   			user to connect to the hosts on the list.
   		DSFC_METHOD_SSH_CONNECT_TIMEOUT=5
   			ssh connect timeout when using "ssh docker ps" method
   		DSFC_METHOD_SSH=1
   			whether to use the "ssh docker ps" method at all
   		DSFC_METHOD_DSM=1
   			whether to use the "docker swarm manager node" method at all
   		DSCF_METHOD_DSM_SERVICE=.
   			if defined, SERVICE_NAME is set to this var value if not implicitly set on command line

   Workflow:
   		Tries the "ssh docker ps" method first, since it's way faster. If the first method failed or disabled, tries "docker swarm manager node" method, that may take a while.


EOM

if [[ $# -eq 0 ]] ; then
    echo "$usage"
    exit 1
fi

case "$1" in
  -h|--help) printf "$usage"
     exit 0
     ;;
esac

if [ ! -z "$2" ]; then
	DSCF_METHOD_DSM_SERVICE="$2"
fi

#
# Trying using the "ssh and docker" ps method
#

DSFC_METHOD_SSH_RESULT=-1 # using unique simple numbers

if (( DSFC_METHOD_SSH == 1 )) ; then

	DSFC_METHOD_SSH_RESULT=0

	for DSFC_HOST in $DSFC_HOSTS_LIST ; do ssh -o ConnectTimeout=$DSFC_METHOD_SSH_CONNECT_TIMEOUT $DSFC_USER'@'$DSFC_HOST 'docker ps | grep '$1' | grep '$DSCF_METHOD_DSM_SERVICE' |sed "s/.*/$(hostname)/"|sort|uniq' || DSFC_METHOD_SSH_RESULT=$? ; done

	if [ -z "$DSFC_HOSTS_LIST" ]; then # if no hosts were found, consider error
		DSFC_METHOD_SSH_RESULT=-3 # using unique simple numbers
	fi

fi

#
# Trying using the slower "swarm manager method" if allowed and ssh method didn't work
#

DSFC_METHOD_DSM_RESULT=1 # if not trying - do not interfere with previous result
if ((DSFC_METHOD_DSM = 1 && DSFC_METHOD_SSH_RESULT != 0)) ; then

	RW_DSM="$(docker node ls)"
	if [[ $? -eq 0 ]] ; then

		SEARCHFOR="$(docker service list --format '{{.Name}}' | tr '\n' ' ' | grep $DSCF_METHOD_DSM_SERVICE )"; ((for f in $(docker service ps -q $SEARCHFOR); do docker inspect --format '{{.Status.ContainerStatus.ContainerID}} {{.NodeID}}' $f; done) | grep $1 | cut -f2 -d' ' | xargs docker node inspect --format "{{.Description.Hostname}}") | sort | uniq

		DSFC_METHOD_DSM_RESULT=$?

	else
		DSFC_METHOD_DSM_RESULT=1 # if not on a docker swarm node, use previous exit codes
	fi

fi

exit $(( DSFC_METHOD_DSM_RESULT * DSFC_METHOD_SSH_RESULT )) # we have simple numbers, so unique exit code, but maybe negative