1. docker
  2. Commit 14835b683453c27c3c324e8cc4cfb702cd968aba
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clarify update-delay and rolling update behavior

Signed-off-by: Charles Smith <charles.smith@docker.com>
(cherry picked from commit 68a9224bd42437e63972dc9c3374c065872363b3)
Signed-off-by: Tibor Vass <tibor@docker.com>

Charles Smith authored on 2016/07/12 12:06:56
Showing 1 changed files
docs/swarm/swarm-tutorial/rolling-update.md
History View file @ 14835b6
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@@ -22,24 +22,34 @@ Redis 3.0.7 container image using rolling updates.
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 run your manager node. For example, the tutorial uses a machine named
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 `manager1`.
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-2. Deploy Redis 3.0.6 to the swarm and configure the swarm to update one node
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-every 10 seconds:
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+2. Deploy Redis 3.0.6 to the swarm and configure the swarm with a 10 second
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+update delay:
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     ```bash
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-    $ docker service create --replicas 3 --name redis --update-delay 10s --update-parallelism 1 redis:3.0.6
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+    $ docker service create \
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+      --replicas 3 \
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+      --name redis \
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+      --update-delay 10s \
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+      --update-parallelism 1 \
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+      redis:3.0.6
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     0u6a4s31ybk7yw2wyvtikmu50
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     ```
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     You configure the rolling update policy at service deployment time.
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-    The `--update-parallelism` flag configures the number of service tasks
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-    to update simultaneously.
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+    The `--update-parallelism` flag configures the number of service tasks that
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+    the scheduler can update simultaneously. When updates to individual tasks
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+    return a state of `RUNNING` or `FAILED`, the scheduler schedules another
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+    task to update until all tasks are updated.
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     The `--update-delay` flag configures the time delay between updates to a
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-    service task or sets of tasks. You can describe the time `T` as a
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-    combination of the number of seconds `Ts`, minutes `Tm`, or hours `Th`. So
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-    `10m30s` indicates a 10 minute 30 second delay.
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+    service task or sets of tasks.
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+
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+    You can describe the time `T` as a combination of the number of seconds
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+    `Ts`, minutes `Tm`, or hours `Th`. So `10m30s` indicates a 10 minute 30
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+    second delay.
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+
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 3. Inspect the `redis` service:
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@@ -51,6 +61,7 @@ every 10 seconds:
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     Mode:           Replicated
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      Replicas:      3
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     Placement:
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+     Strategy:	    Spread
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     UpdateConfig:
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      Parallelism:   1
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      Delay:         10s
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@@ -67,6 +78,14 @@ applies the update to nodes according to the `UpdateConfig` policy:
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     redis
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     ```
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+    The scheduler applies rolling updates as follows:
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+
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+    * Stop the initial number of tasks according to `--update-parallelism`.
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+    * Schedule updates for the stopped tasks.
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+    * Start the containers for the updated tasks.
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+    * After an update to a task completes, wait for the specified delay
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+    period before stopping the next task.
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+
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 5. Run `docker service inspect --pretty redis` to see the new image in the
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 desired state:
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@@ -78,13 +97,14 @@ desired state:
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     Mode:           Replicated
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      Replicas:      3
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     Placement:
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+     Strategy:	    Spread
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     UpdateConfig:
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      Parallelism:   1
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      Delay:         10s
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     ContainerSpec:
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      Image:         redis:3.0.7
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     Resources:
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-   ```
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+    ```
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 6. Run `docker service tasks <TASK-ID>` to watch the rolling update:
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@@ -99,7 +119,6 @@ desired state:
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     Before Swarm updates all of the tasks, you can see that some are running
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     `redis:3.0.6` while others are running `redis:3.0.7`. The output above shows
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-    the state once the rolling updates are done. You can see that each instances
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-    entered the `RUNNING` state in approximately 10 second increments.
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+    the state once the rolling updates are done.
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 Next, learn about how to [drain a node](drain-node.md) in the Swarm.