Docs fix for restart issue with orchestrated minio stack (#6606) (#6613)

docs/orchestration/docker-swarm/README.md

@@ -34,6 +34,19 @@ echo "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY" | docker secret create secret_ke
 
 ## 4. Deploy distributed Minio services
 
+The example Minio stack uses 4 Docker volumes, which are created automatically by deploying the stack. We have to make sure that the services in the stack are always (re)started on the same node, where the service is deployed the first time. 
+Otherwise Docker will create a new volume upon restart of the service on another Docker node, which is not in sync with the other volumes and the stack will fail to start healthy. 
+Before deploying the stack, add labels to the Docker nodes where you want the minio services to run:
+
+```
+docker node update --label-add minio1=true <DOCKER-NODE1>
+docker node update --label-add minio2=true <DOCKER-NODE2>
+docker node update --label-add minio3=true <DOCKER-NODE3>
+docker node update --label-add minio4=true <DOCKER-NODE4>
+```
+
+It is possible to run more than one minio service on one Docker Node. Set the labels accordingly.
+
 Download the [Docker Compose file](https://github.com/minio/minio/blob/master/docs/orchestration/docker-swarm/docker-compose-secrets.yaml?raw=true) on your Swarm master. Then execute the command
 
 ```shell

docs/orchestration/docker-swarm/docker-compose-secrets.yaml

@@ -3,6 +3,7 @@ version: '3.1'
 services:
   minio1:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio1
     volumes:
       - minio1-data:/export
     ports:
@@ -14,6 +15,9 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio1==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
     secrets:
       - secret_key
@@ -21,6 +25,7 @@ services:
 
   minio2:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio2
     volumes:
       - minio2-data:/export
     ports:
@@ -32,6 +37,9 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio2==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
     secrets:
       - secret_key
@@ -39,6 +47,7 @@ services:
 
   minio3:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio3
     volumes:
       - minio3-data:/export
     ports:
@@ -50,6 +59,9 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio3==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
     secrets:
       - secret_key
@@ -57,6 +69,7 @@ services:
 
   minio4:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio4
     volumes:
       - minio4-data:/export
     ports:
@@ -68,6 +81,9 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio4==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
     secrets:
       - secret_key

docs/orchestration/docker-swarm/docker-compose.yaml

@@ -3,6 +3,7 @@ version: '3'
 services:
   minio1:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio1
     volumes:
       - minio1-data:/export
     ports:
@@ -17,10 +18,14 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio1==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
 
   minio2:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio2
     volumes:
       - minio2-data:/export
     ports:
@@ -35,10 +40,14 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio2==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
 
   minio3:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio3
     volumes:
       - minio3-data:/export
     ports:
@@ -53,10 +62,14 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio3==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
 
   minio4:
     image: minio/minio:RELEASE.2018-10-06T00-15-16Z
+    hostname: minio4
     volumes:
       - minio4-data:/export
     ports:
@@ -71,6 +84,9 @@ services:
         delay: 10s
         max_attempts: 10
         window: 60s
+      placement:
+        constraints:
+          - node.labels.minio4==true
     command: server http://minio1/export http://minio2/export http://minio3/export http://minio4/export
 
 volumes: