Fall back to default behavior when deployed to a worker node (#593)

* Add test demonstrating failure when running on worker node

* Consider manager status when checking for swarm related features

* Update documentation

cmd/backup/stop_restart.go

@@ -89,7 +89,7 @@ func isSwarm(c interface {
 	if err != nil {
 		return false, errwrap.Wrap(err, "error getting docker info")
 	}
-	return info.Swarm.LocalNodeState != "" && info.Swarm.LocalNodeState != swarm.LocalNodeStateInactive, nil
+	return info.Swarm.LocalNodeState != "" && info.Swarm.LocalNodeState != swarm.LocalNodeStateInactive && info.Swarm.ControlAvailable, nil
 }
 
 // stopContainersAndServices stops all Docker containers that are marked as to being

cmd/backup/stop_restart_test.go

@@ -30,13 +30,26 @@ func TestIsSwarm(t *testing.T) {
 			&mockInfoClient{
 				result: system.Info{
 					Swarm: swarm.Info{
-						LocalNodeState: swarm.LocalNodeStateActive,
+						LocalNodeState:   swarm.LocalNodeStateActive,
+						ControlAvailable: true,
 					},
 				},
 			},
 			true,
 			false,
 		},
+		{
+			"worker",
+			&mockInfoClient{
+				result: system.Info{
+					Swarm: swarm.Info{
+						LocalNodeState: swarm.LocalNodeStateActive,
+					},
+				},
+			},
+			false,
+			false,
+		},
 		{
 			"compose",
 			&mockInfoClient{

docs/how-tos/use-with-docker-swarm.md

@@ -8,7 +8,8 @@ nav_order: 13
 # Use with Docker Swarm
 
 {: .note }
-The mechanisms described in this page __do only apply when Docker is running in [Swarm mode][swarm]__.
+The mechanisms described in this page __do only apply when Docker is running in [Swarm mode][swarm]__ and __when placing the `docker-volume-backup` container on a manager node__.
+Containers that are placed on worker nodes function as if the Docker engine is not running in Swarm mode, i.e. there is no access to services and there is no way to interact with resources that are running on different host nodes.
 
 [swarm]: https://docs.docker.com/engine/swarm/
 

test/README.md

@@ -67,3 +67,11 @@ A test case can signal it wants to run in swarm mode by placing an empty `.swarm
 In case the swarm setup should be compose of multiple nodes, a `.multinode` file can be used.
 
 A multinode setup will contain one manager (`manager`) and two worker nodes (`worker1` and `worker2`).
+
+If a test is expected to run in the context of a node other than the `manager`, the hostname can be put in the `.multinode` file.
+
+> [!IMPORTANT]
+> When running against a multi-node setup and targeting a non-manager node, the test script will automatically deploy a stack named `test_stack` based on the compose file in the test directory.
+> This is required because the non-manager node cannot deploy the stack itself from within the test script.
+> This also means, you cannot mount local directories created in your test script, as the containers are already created when the script runs.
+> You can work around this limitation by creating named volumes and then `docker cp`ing the contents your test needs to inspect.

test/docker-compose.yml

@@ -1,5 +1,6 @@
 services:
   manager: &node
+    hostname: manager
     privileged: true
     image: offen/docker-volume-backup:test-sandbox
     healthcheck:
@@ -8,17 +9,19 @@ services:
       timeout: 5s
       retries: 50
     volumes:
-      - $SOURCE:/code
-      - $TARBALL:/cache/image.tar.gz
+      - ./:/code
+      - ${TARBALL:-.}:/cache/image.tar.gz
       - docker_volume_backup_test_sandbox_image:/var/lib/docker/image
       - docker_volume_backup_test_sandbox_overlay2:/var/lib/docker/overlay2
 
   worker1:
     <<: *node
+    hostname: worker1
     profiles:
       - multinode
   worker2:
     <<: *node
+    hostname: worker2
     profiles:
       - multinode
 

test/test.sh

@@ -45,6 +45,12 @@ for dir in $(find $find_args | sort); do
   fi
 
   docker compose --profile $compose_profile up -d --wait
+  test_context=manager
+  if [ -f "${dir}/.multinode" ] && [ -s "${dir}/.multinode" ]; then
+    test_context=$(cat $dir/.multinode)
+    echo "Running tests on $test_context instead of manager"
+  fi
+  docker compose exec $test_context /bin/sh -c "docker load -i /cache/image.tar.gz"
 
   if [ -f "${dir}/.swarm" ]; then
     docker compose exec manager docker swarm init
@@ -54,10 +60,13 @@ for dir in $(find $find_args | sort); do
     token=$(docker compose exec manager docker swarm join-token -q worker)
     docker compose exec worker1 docker swarm join --token $token $manager_ip:2377
     docker compose exec worker2 docker swarm join --token $token $manager_ip:2377
+
+    if [ "$test_context" != "manager" ]; then
+      docker compose exec -w "/code/$dir" manager docker stack deploy --compose-file="docker-compose.yml" test_stack
+    fi
   fi
 
-  docker compose exec manager /bin/sh -c "docker load -i /cache/image.tar.gz"
-  docker compose exec -e TEST_VERSION=$IMAGE_TAG manager /bin/sh -c "/code/test/$test"
+  docker compose exec -e TEST_VERSION=$IMAGE_TAG $test_context /bin/sh -c "/code/$test"
 
   docker compose --profile $compose_profile down
   echo ""

test/worker-node/.multinode

@@ -0,0 +1 @@
+worker1

test/worker-node/docker-compose.yml

@@ -0,0 +1,56 @@
+services:
+  database:
+    image: mariadb:10.7
+    deploy:
+      restart_policy:
+        condition: on-failure
+      placement:
+        constraints:
+          - node.hostname == worker1
+    environment:
+      MARIADB_ROOT_PASSWORD: test
+      MARIADB_DATABASE: backup
+    labels:
+      - docker-volume-backup.archive-pre=/bin/sh -c 'mysqldump -ptest --all-databases > /tmp/volume/dump.sql'
+      - docker-volume-backup.copy-post=/bin/sh -c 'echo "post" > /tmp/volume/post.txt'
+      - docker-volume-backup.stop-during-backup=true
+    volumes:
+      - app_data:/tmp/volume
+
+  other_database:
+    image: mariadb:10.7
+    deploy:
+      placement:
+        constraints:
+          - node.hostname == manager
+      restart_policy:
+        condition: on-failure
+    environment:
+      MARIADB_ROOT_PASSWORD: test
+      MARIADB_DATABASE: backup
+    labels:
+      - docker-volume-backup.archive-pre=touch /tmp/volume/not-relevant.txt
+      - docker-volume-backup.exec-label=not-relevant
+    volumes:
+      - app_data:/tmp/volume
+
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    deploy:
+      restart_policy:
+        condition: on-failure
+      placement:
+        constraints:
+          - node.hostname == worker1
+    environment:
+      BACKUP_FILENAME: test.tar.gz
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      EXEC_FORWARD_OUTPUT: "true"
+    volumes:
+      - backup_archive:/archive
+      - app_data:/backup/data:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+
+volumes:
+  app_data:
+  backup_archive:

test/worker-node/run.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+export TMP_DIR=$(mktemp -d)
+export LOCAL_DIR=$(mktemp -d)
+
+while [ -z $(docker ps -q -f name=backup) ]; do
+  info "Backup container not ready yet. Retrying."
+  sleep 1
+done
+
+sleep 20
+
+docker exec $(docker ps -q -f name=backup) backup
+
+mkdir -p /archive
+docker cp $(docker ps -q -f name=backup):/archive $LOCAL_DIR
+
+tar -xvf "$LOCAL_DIR/archive/test.tar.gz" -C $TMP_DIR
+if [ ! -f "$TMP_DIR/backup/data/dump.sql" ]; then
+  fail "Could not find file written by pre command."
+fi
+pass "Found expected file."
+
+if [ -f "$TMP_DIR/backup/data/post.txt" ]; then
+  fail "File created in post command was present in backup."
+fi
+pass "Did not find unexpected file."