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From vvasu...@apache.org
Subject [12/50] [abbrv] hadoop git commit: YARN-5311. Document graceful decommission CLI and usage. Contributed by Elek, Marton.
Date Mon, 03 Jul 2017 08:54:22 GMT
YARN-5311. Document graceful decommission CLI and usage. Contributed by Elek, Marton.

Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/4e3eebc9
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/4e3eebc9
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/4e3eebc9

Branch: refs/heads/YARN-3926
Commit: 4e3eebc943835077e3dd0df9e0b9239ae604cb89
Parents: 990aa34
Author: Junping Du <junping_du@apache.org>
Authored: Wed Jun 28 15:32:04 2017 -0700
Committer: Junping Du <junping_du@apache.org>
Committed: Wed Jun 28 15:32:04 2017 -0700

 .../hadoop/yarn/conf/YarnConfiguration.java     |   4 +
 .../src/site/markdown/GracefulDecommission.md   | 168 +++++++++++++++++++
 .../src/site/markdown/ResourceManagerRest.md    |   2 +-
 3 files changed, 173 insertions(+), 1 deletion(-)

diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java
index ca71d35..a6d3360 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java
@@ -831,6 +831,10 @@ public class YarnConfiguration extends Configuration {
       RM_PREFIX + "nodemanager-graceful-decommission-timeout-secs";
   public static final int DEFAULT_RM_NODE_GRACEFUL_DECOMMISSION_TIMEOUT = 3600;
+  /**
+   * Period in seconds of the poll timer task inside DecommissioningNodesWatcher
+   * to identify and take care of DECOMMISSIONING nodes missing regular heart beat.
+   */
       RM_PREFIX + "decommissioning-nodes-watcher.poll-interval-secs";
   public static final int

diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/GracefulDecommission.md
new file mode 100644
index 0000000..2acb3d2
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/GracefulDecommission.md
@@ -0,0 +1,168 @@
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+   http://www.apache.org/licenses/LICENSE-2.0
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  See the License for the specific language governing permissions and
+  limitations under the License. See accompanying LICENSE file.
+Graceful Decommission of Yarn Nodes
+* [Overview](#overview)
+* [Features](#features)
+  * [NodesListManager detects and handles include and exclude list changes](#nodeslistmanager-detects-and-handles-include-and-exclude-list-changes)
+  * [RMNode handles decommission events](#rmnode-handles-decommission-events)
+  * [Automatic and asynchronous tracking of decommissioning nodes status](#automatic-and-asynchronous-tracking-of-decommissioning-nodes-status)
+  * [Per-Node decommission timeout support](#per-node-decommission-timeout-support)
+* [Configuration](#configuration)
+Yarn is scalable very easily: any new NodeManager could join to the configured ResourceManager
and start to execute jobs. But to achieve full elasticity we need a decommissioning process
which helps to remove existing nodes and down-scale the cluster.
+Yarn Nodes could be decommissioned NORMAL or GRACEFUL.
+Normal Decommission of Yarn Nodes means an immediate shutdown.
+Graceful Decommission of Yarn Nodes is the mechanism to decommission NMs while minimize the
impact to running applications. Once a node is in DECOMMISSIONING state, RM won't schedule
new containers on it and will wait for running containers and applications to complete (or
until decommissioning timeout exceeded) before transition the node into DECOMMISSIONED.
+## Quick start
+To do a normal decommissioning:
+1. Start a Yarn cluster (with NodeManageres and ResourceManager)
+2. Start a yarn job (for example with `yarn jar...` )
+3. Add `yarn.resourcemanager.nodes.exclude-path` property to your `yarn-site.xml` (Note:
you don't need to restart the ResourceManager)
+4. Create a text file (the location is defined in the previous step) with one line which
contains the name of a selected NodeManager 
+5. Call `./bin/yarn rmadmin  -refreshNodes`
+6. Result: The nodemanager is decommissioned *immediately*
+In the next sections we will cover some more detailed usage (for example: using graceful
decommissioning with timeout).
+###Trigger decommission/recommission based on exclude/include lists
+`yarn rmadmin -refreshNodes [-g [timeout in seconds] -client|server]` notifies NodesListManager
to detect and handle include and exclude hosts changes. NodesListManager loads excluded hosts
from the exclude file as specified through the `yarn.resourcemanager.nodes.exclude-path` configuration
in yarn-site.xml. (Note:  It is unnecessary to restart RM in case of changing the exclude-path

+as this config will be read again for every `refreshNodes` command)
+The format of the file could be plain text or XML depending the extension of the file. Only
the XML format supports per node timout for graceful decommissioning.
+NodesListManager inspects and compares status of RMNodes in resource manager and the exclude
list, and apply necessary actions based on following rules:
+* Recommission DECOMMISSIONED or DECOMMISSIONING nodes that are no longer excluded;
+* Gracefully decommission excluded nodes that are not already in DECOMMISSIONED nor
+* _Immediately_ decommission excluded nodes that are not already in DECOMMISSIONED state
if `-g` flag is not specified.
to the RMNode.
+###Per-Node decommission timeout support
+To support flexible graceful decommission of nodes using different timeout through
+single or multiple refreshNodes requests, HostsFileReader supports optional timeout value
+after each hostname (or ip) in the exclude host file. 
+The effective decommissioning timeout to use for a particular host is based on following
+In case of server side timeout:
+1. Use the timeout for the particular host if specified in exclude host file;
+2. Use the timeout in `yarn rmadmin -refreshNodes -g [timeout in seconds] -server|client`
if specified;
+3. Use the default timeout specified through *"yarn.resourcemanager.nodemanager-graceful-decommission-timeout-secs"*
+In case of client side timout (see bellow):
+1. Only the command line parameter defined by the `-g` flag will be used. 
+NodesListManager decides the effective timeout to use and set it on individual RMNode.
+The timeout could also be dynamically adjusted through `yarn rmadmin -refreshNodes -g [timeout
in seconds]` command. NodesListManager will resolve the effective timeout to use and update
RMNode as necessary of the new timeout. Change of timeout does not reset the ongoing decommissioning
but only affect the evaluation of whether the node has reached decommissioning timeout.
+Here is a sample excludes file in xml format.
+<?xml version="1.0"?>
+  <host><name>host1</name></host>
+  <host><name>host2</name><timeout>123</timeout></host>
+  <host><name>host3</name><timeout>-1</timeout></host>
+  <host><name>host4, host5,host6</name><timeout>1800</timeout></host>
+If the file extension of the exclude file is not xml, standard one-line-per-host format is
used without timeout support.
+Note: In the future more file formats are planned with timeout support. Follow the [YARN-5536](https://issues.apache.org/jira/browse/YARN-5536)
if you are interested. 
+Important to mention, that the timeout is not persited. In case of a RM restart/failover
the node will be immediatelly decommission. (Follow the [YARN-5464](https://issues.apache.org/jira/browse/YARN-5464)
for changes in this behavior).
+### Client or server side timeout
+Timeout of Graceful decommissioning could be tracked on server or client side. The `-client|server`
indicates if the timeout tracking should be handled by the client or the ResourceManager.
The client side tracking is blocking, while the server-side tracking is not.
+###RMNode handles decommission events
+Upon receiving GRACEFUL_DECOMMISSION event, the RMNode will save the decommissioning timeout
if specified, update metrics for graceful decommission and preserve its original total capacity,
and transition into DECOMMISSIONING state.
+Resources will be dynamically and periodically updated on DECOMMISSIONING RMNode so that
scheduler won't be scheduling new containers on them due to no available resources.
+###Automatic and asynchronous tracking of decommissioning nodes status
+**DecommissioningNodeWatcher** is the YARN component that tracks DECOMMISSIONING nodes
+status automatically and asynchronously after client/admin made the graceful decommission
+request. NM periodically send RM heart beat with it latest container status.
+DecommissioningNodeWatcher tracks heartbeat updates on all DECOMMISSIONING nodes to decide
+after all running containers on the node have completed, will be transitioned into DECOMMISSIONED
+after which NodeManager will be told to shutdown.
+Under MR application, a node, after completes all its containers, may still serve it map
output data
+during the duration of the application for reducers. The YARN graceful decommission
+mechanism keeps such DECOMMISSIONING nodes until all involved applications complete.
+It could be however undesirable under long-running applications scenario where a bunch of
+"idle" nodes might stay around for long period of time. DecommissioningNodeWatcher
+balances such concern with a timeout --- a DECOMMISSIONING node will be DECOMMISSIONED
+no later than decommissioning timeout regardless of running containers or applications.
+If running containers finished earlier, it continues waiting for applications to finish
+until the decommissioning timeout. When decommissioning timeout reaches, the node
+will be decommissioned regardless. The node will be deactivated and owning tasks will
+be rescheduled as necessary.
+Status of all decommissioning node are logged periodically (every 20 seconds) in resource
manager logs.
+Following are the sub-status of a decommissioning node:
+* NONE --- Node is not in DECOMMISSIONING state.
+* WAIT_CONTAINER --- Wait for running containers to complete.
+* WAIT_APP --- Wait for running application to complete (after all containers complete)
+* TIMEOUT --- Timeout waiting for either containers or applications to complete
+* READY --- Nothing to wait, ready to be decommissioned
+* DECOMMISSIONED --- The node has already been decommissioned
+| Property                                 | Value                                    |
+| ---------------------------------------- | ---------------------------------------- |
+| yarn.resourcemanager.nodemanager-graceful-decommission-timeout-secs | Timeout in seconds
for YARN node graceful decommission. This is the maximal time to wait for running containers
and applications to complete before transition a DECOMMISSIONING node into DECOMMISSIONED.
The default value is 3600 seconds. Negative value (like -1) is handled as infinite timeout.
+| yarn.resourcemanager.decommissioning-nodes-watcher.poll-interval-secs | Period in seconds
of the poll timer task inside DecommissioningNodesWatcher to identify and take care of DECOMMISSIONING
nodes missing regular heart beat. The default value is 20 seconds. |
+| yarn.resourcemanager.nodes.exclude-path  | Path to file with nodes to exclude.      |
+| yarn.resourcemanager.nodes.include-path  | Path to file with nodes to include.      |

diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/ResourceManagerRest.md
index 48dea5a..c119651 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/ResourceManagerRest.md
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/ResourceManagerRest.md
@@ -2112,7 +2112,7 @@ Use the following URI to obtain a Node Object, from a node identified
by the nod
 | Item | Data Type | Description |
 |:---- |:---- |:---- |
 | rack | string | The rack location of this node |
-| state | string | State of the node - valid values are: NEW, RUNNING, UNHEALTHY, DECOMMISSIONED,
+| state | string | State of the node - valid values are: NEW, RUNNING, UNHEALTHY, DECOMMISSIONING,
 | id | string | The node id |
 | nodeHostName | string | The host name of the node |
 | nodeHTTPAddress | string | The nodes HTTP address |

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