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[#27,#28] swarm: add init-eg-swarm,docker-compose.swarm.yml
Per discussions in: - #27 - #28
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‎README.md

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```
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## Clustering (Swarm; Automatically)
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If you're running on Docker Swarm, you can use the provided example
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`docker-compose.swarm.yml` as a starting point, deploying with
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`docker stack deploy`, along with the init script. Note that the example makes
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various assumptions, such as that the Swarm node is a manager, that it is tagged
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with `grp=dbxl`, and that `db_a` has a lower subnet than `db_b` (which might or
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might not happen automatically; create the networks manually, if you're having
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trouble).
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```sh
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bin/init-eg-swarm STACK_NAME
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```
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Note there are various caveats to using this, which you can read about in detail
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here:
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- https://github.com/pavouk-0/postgres-xl-docker/issues/27
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- https://github.com/pavouk-0/postgres-xl-docker/pull/28
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## Clustering (Manually)
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Prepare a clustering query, able to be executed on each node. Simplest is to use

‎bin/init-eg-swarm

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#!/bin/bash -u
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stack=$1
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nodes=(db_coord_1 db_coord_2 db_data_1 db_data_2)
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PG_USER_HEALTHCHECK=_healthcheck
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#-------------------------------------------------------------------------------
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function log() {
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local msg="$*"
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echo "$(date -Is), $msg"
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}
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function startup() {
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log "========================================"
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}
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function shutdown() {
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log "----------------------------------------"
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}
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function srv() {
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local node=$1
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shift
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docker exec "$node" "$@"
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}
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function cmd() {
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local node=$1
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shift
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log "$@"
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srv "$node" psql -c "$@"
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}
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function get_container() {
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local node=$1
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id=$(docker service ps -f 'desired-state=running' -q "${stack}_${node}" |
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head -n1)
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echo "${stack}_${node}.1.${id}"
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}
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function get_healthcheck() {
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local node=$1
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docker service inspect "${stack}_${node}" \
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-f '{{ index .Spec.TaskTemplate.ContainerSpec.Healthcheck.Test 1 }}'
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}
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trap shutdown EXIT
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#-------------------------------------------------------------------------------
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startup
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for node in "${nodes[@]}" ; do
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ctnr=$(get_container "$node")
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cmd "$ctnr" "CREATE NODE coord_1 WITH (TYPE = 'coordinator', HOST = 'db_coord_1', PORT = 5432);"
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cmd "$ctnr" "CREATE NODE coord_2 WITH (TYPE = 'coordinator', HOST = 'db_coord_2', PORT = 5432);"
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cmd "$ctnr" "CREATE NODE data_1 WITH (TYPE = 'datanode', HOST = 'db_data_1', PORT = 5432);"
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cmd "$ctnr" "CREATE NODE data_2 WITH (TYPE = 'datanode', HOST = 'db_data_2', PORT = 5432);"
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cmd "$ctnr" "ALTER NODE coord_1 WITH (TYPE = 'coordinator', HOST = 'db_coord_1', PORT = 5432);"
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cmd "$ctnr" "ALTER NODE coord_2 WITH (TYPE = 'coordinator', HOST = 'db_coord_2', PORT = 5432);"
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cmd "$ctnr" "ALTER NODE data_1 WITH (TYPE = 'datanode', HOST = 'db_data_1', PORT = 5432);"
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cmd "$ctnr" "ALTER NODE data_2 WITH (TYPE = 'datanode', HOST = 'db_data_2', PORT = 5432);"
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cmd "$ctnr" "SELECT pgxc_pool_reload();"
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cmd "$ctnr" "SELECT * FROM pgxc_node;"
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done
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for node in "${nodes[@]}" ; do
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healthcheck=$(get_healthcheck "$node")
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docker service update "${stack}_${node}" \
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--health-cmd "$healthcheck || true"
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done
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while true ; do
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log "WAITING"
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for node in "${nodes[@]}" ; do
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ctnr=$(get_container "$node")
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srv "$ctnr" psql -tc "SELECT 1 FROM pg_database
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WHERE datname = '${PG_USER_HEALTHCHECK}'" |
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grep -q 1 && break 2
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done
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sleep 1
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done
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log "REDEPLOY stack now !" # to reset healthchecks, and reboot

‎docker-compose.swarm.yml

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version: "3.7"
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services:
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#-----------------------------------------------------------------------------
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db_gtm_1:
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environment:
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- PG_HOST=0.0.0.0
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- PG_NODE=gtm_1
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- PG_PORT=6666
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image: pavouk0/postgres-xl:latest # pin for prod !
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command: docker-cmd-gtm
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entrypoint: docker-entrypoint-gtm
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volumes:
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- db_gtm_1:/var/lib/postgresql
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networks:
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- db_a
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healthcheck:
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test: ["CMD", "docker-healthcheck-gtm"]
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deploy:
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placement:
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constraints:
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- node.labels.grp == dbxl # assumes shared volume storage, or 1-node
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db_coord_1:
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environment:
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- PG_GTM_HOST=db_gtm_1
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- PG_GTM_PORT=6666
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- PG_HOST=0.0.0.0
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- PG_NODE=coord_1
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- PG_PORT=5432
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image: pavouk0/postgres-xl:latest # pin for prod !
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command: docker-cmd-coord
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entrypoint: docker-entrypoint-coord
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volumes:
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- db_coord_1:/var/lib/postgresql
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networks:
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- db_a
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- db_b
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healthcheck:
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test: ["CMD", "docker-healthcheck-coord"]
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deploy:
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placement:
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constraints:
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- node.labels.grp == dbxl # assumes shared volume storage, or 1-node
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db_coord_2:
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environment:
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- PG_GTM_HOST=db_gtm_1
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- PG_GTM_PORT=6666
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- PG_HOST=0.0.0.0
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- PG_NODE=coord_2
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- PG_PORT=5432
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image: pavouk0/postgres-xl:latest # pin for prod !
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command: docker-cmd-coord
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entrypoint: docker-entrypoint-coord
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volumes:
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- db_coord_2:/var/lib/postgresql
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networks:
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- db_a
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- db_b
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healthcheck:
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test: ["CMD", "docker-healthcheck-coord"]
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deploy:
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placement:
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constraints:
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- node.labels.grp == dbxl # assumes shared volume storage, or 1-node
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db_data_1:
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environment:
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- PG_GTM_HOST=db_gtm_1
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- PG_GTM_PORT=6666
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- PG_HOST=0.0.0.0
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- PG_NODE=data_1
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- PG_PORT=5432
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image: pavouk0/postgres-xl:latest # pin for prod !
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command: docker-cmd-data
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entrypoint: docker-entrypoint-data
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volumes:
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- db_data_1:/var/lib/postgresql
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networks:
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- db_a
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healthcheck:
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test: ["CMD", "docker-healthcheck-data"]
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deploy:
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placement:
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constraints:
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- node.labels.grp == dbxl # assumes shared volume storage, or 1-node
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db_data_2:
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environment:
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- PG_GTM_HOST=db_gtm_1
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- PG_GTM_PORT=6666
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- PG_HOST=0.0.0.0
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- PG_NODE=data_2
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- PG_PORT=5432
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image: pavouk0/postgres-xl:latest # pin for prod !
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command: docker-cmd-data
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entrypoint: docker-entrypoint-data
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volumes:
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- db_data_2:/var/lib/postgresql
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networks:
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- db_a
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healthcheck:
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test: ["CMD", "docker-healthcheck-data"]
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deploy:
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placement:
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constraints:
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- node.labels.grp == dbxl # assumes shared volume storage, or 1-node
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#-----------------------------------------------------------------------------
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volumes:
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db_gtm_1: {}
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db_coord_1: {}
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db_coord_2: {}
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db_data_1: {}
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db_data_2: {}
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networks:
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db_a:
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driver: overlay
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internal: true
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db_b:
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driver: overlay
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internal: true

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