|
|
@@ -0,0 +1,208 @@
|
|
|
+~~ 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,
|
|
|
+~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
|
+~~ See the License for the specific language governing permissions and
|
|
|
+~~ limitations under the License. See accompanying LICENSE file.
|
|
|
+
|
|
|
+ ---
|
|
|
+ ResourceManger Restart
|
|
|
+ ---
|
|
|
+ ---
|
|
|
+ ${maven.build.timestamp}
|
|
|
+
|
|
|
+ResourceManger Restart
|
|
|
+
|
|
|
+%{toc|section=1|fromDepth=0}
|
|
|
+
|
|
|
+* {Overview}
|
|
|
+
|
|
|
+ ResourceManager is the central authority that manages resources and schedules
|
|
|
+ applications running atop of YARN. Hence, it is potentially a single point of
|
|
|
+ failure in a Apache YARN cluster.
|
|
|
+
|
|
|
+ This document gives an overview of ResourceManager Restart, a feature that
|
|
|
+ enhances ResourceManager to keep functioning across restarts and also makes
|
|
|
+ ResourceManager down-time invisible to end-users.
|
|
|
+
|
|
|
+ ResourceManager Restart feature is divided into two phases:
|
|
|
+
|
|
|
+ ResourceManager Restart Phase 1: Enhance RM to persist application/attempt state
|
|
|
+ and other credentials information in a pluggable state-store. RM will reload
|
|
|
+ this information from state-store upon restart and re-kick the previously
|
|
|
+ running applications. Users are not required to re-submit the applications.
|
|
|
+
|
|
|
+ ResourceManager Restart Phase 2:
|
|
|
+ Focus on re-constructing the running state of ResourceManger by reading back
|
|
|
+ the container statuses from NodeMangers and container requests from ApplicationMasters
|
|
|
+ upon restart. The key difference from phase 1 is that previously running applications
|
|
|
+ will not be killed after RM restarts, and so applications won't lose its work
|
|
|
+ because of RM outage.
|
|
|
+
|
|
|
+ As of Hadoop 2.4.0 release, only ResourceManager Restart Phase 1 is implemented which
|
|
|
+ is described below.
|
|
|
+
|
|
|
+* {Feature}
|
|
|
+
|
|
|
+ The overall concept is that RM will persist the application metadata
|
|
|
+ (i.e. ApplicationSubmissionContext) in
|
|
|
+ a pluggable state-store when client submits an application and also saves the final status
|
|
|
+ of the application such as the completion state (failed, killed, finished)
|
|
|
+ and diagnostics when the application completes. Besides, RM also saves
|
|
|
+ the credentials like security keys, tokens to work in a secure environment.
|
|
|
+ Any time RM shuts down, as long as the required information (i.e.application metadata
|
|
|
+ and the alongside credentials if running in a secure environment) is available
|
|
|
+ in the state-store, when RM restarts, it can pick up the application metadata
|
|
|
+ from the state-store and re-submit the application. RM won't re-submit the
|
|
|
+ applications if they were already completed (i.e. failed, killed, finished)
|
|
|
+ before RM went down.
|
|
|
+
|
|
|
+ NodeMangers and clients during the down-time of RM will keep polling RM until
|
|
|
+ RM comes up. When RM becomes alive, it will send a re-sync command to
|
|
|
+ all the NodeMangers and ApplicationMasters it was talking to via heartbeats.
|
|
|
+ Today, the behaviors for NodeMangers and ApplicationMasters to handle this command
|
|
|
+ are: NMs will kill all its managed containers and re-register with RM. From the
|
|
|
+ RM's perspective, these re-registered NodeManagers are similar to the newly joining NMs.
|
|
|
+ AMs(e.g. MapReduce AM) today are expected to shutdown when they receive the re-sync command.
|
|
|
+ After RM restarts and loads all the application metadata, credentials from state-store
|
|
|
+ and populates them into memory, it will create a new
|
|
|
+ attempt (i.e. ApplicationMaster) for each application that was not yet completed
|
|
|
+ and re-kick that application as usual. As described before, the previously running
|
|
|
+ applications' work is lost in this manner since they are essentially killed by
|
|
|
+ RM via the re-sync command on restart.
|
|
|
+
|
|
|
+* {Configurations}
|
|
|
+
|
|
|
+ This section describes the configurations involved to enable RM Restart feature.
|
|
|
+
|
|
|
+ * Enable ResourceManager Restart functionality.
|
|
|
+
|
|
|
+ To enable RM Restart functionality, set the following property in <<conf/yarn-site.xml>> to true:
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Value |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.recovery.enabled>>> | |
|
|
|
+| | <<<true>>> |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+
|
|
|
+ * Configure the state-store that is used to persist the RM state.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.store.class>>> | |
|
|
|
+| | The class name of the state-store to be used for saving application/attempt |
|
|
|
+| | state and the credentials. The available state-store implementations are |
|
|
|
+| | <<<org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore>>> |
|
|
|
+| | , a ZooKeeper based state-store implementation and |
|
|
|
+| | <<<org.apache.hadoop.yarn.server.resourcemanager.recovery.FileSystemRMStateStore>>> |
|
|
|
+| | , a Hadoop FileSystem based state-store implementation like HDFS. |
|
|
|
+| | The default value is set to |
|
|
|
+| | <<<org.apache.hadoop.yarn.server.resourcemanager.recovery.FileSystemRMStateStore>>>. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ * Configurations when using Hadoop FileSystem based state-store implementation.
|
|
|
+
|
|
|
+ Configure the URI where the RM state will be saved in the Hadoop FileSystem state-store.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.fs.state-store.uri>>> | |
|
|
|
+| | URI pointing to the location of the FileSystem path where RM state will |
|
|
|
+| | be stored (e.g. hdfs://localhost:9000/rmstore). |
|
|
|
+| | Default value is <<<${hadoop.tmp.dir}/yarn/system/rmstore>>>. |
|
|
|
+| | If FileSystem name is not provided, <<<fs.default.name>>> specified in |
|
|
|
+| | <<conf/core-site.xml>> will be used. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ Configure the retry policy state-store client uses to connect with the Hadoop
|
|
|
+ FileSystem.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.fs.state-store.retry-policy-spec>>> | |
|
|
|
+| | Hadoop FileSystem client retry policy specification. Hadoop FileSystem client retry |
|
|
|
+| | is always enabled. Specified in pairs of sleep-time and number-of-retries |
|
|
|
+| | i.e. (t0, n0), (t1, n1), ..., the first n0 retries sleep t0 milliseconds on |
|
|
|
+| | average, the following n1 retries sleep t1 milliseconds on average, and so on. |
|
|
|
+| | Default value is (2000, 500) |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ * Configurations when using ZooKeeper based state-store implementation.
|
|
|
+
|
|
|
+ Configure the ZooKeeper server address and the root path where the RM state is stored.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-address>>> | |
|
|
|
+| | Comma separated list of Host:Port pairs. Each corresponds to a ZooKeeper server |
|
|
|
+| | (e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002") to be used by the RM |
|
|
|
+| | for storing RM state. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-state-store.parent-path>>> | |
|
|
|
+| | The full path of the root znode where RM state will be stored. |
|
|
|
+| | Default value is /rmstore. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ Configure the retry policy state-store client uses to connect with the ZooKeeper server.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-num-retries>>> | |
|
|
|
+| | Number of times RM tries to connect to ZooKeeper server if the connection is lost. |
|
|
|
+| | Default value is 500. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-retry-interval-ms>>> |
|
|
|
+| | The interval in milliseconds between retries when connecting to a ZooKeeper server. |
|
|
|
+| | Default value is 2 seconds. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-timeout-ms>>> | |
|
|
|
+| | ZooKeeper session timeout in milliseconds. This configuration is used by |
|
|
|
+| | the ZooKeeper server to determine when the session expires. Session expiration |
|
|
|
+| | happens when the server does not hear from the client (i.e. no heartbeat) within the session |
|
|
|
+| | timeout period specified by this configuration. Default |
|
|
|
+| | value is 10 seconds |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ Configure the ACLs to be used for setting permissions on ZooKeeper znodes.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.zk-acl>>> | |
|
|
|
+| | ACLs to be used for setting permissions on ZooKeeper znodes. Default value is <<<world:anyone:rwcda>>> |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ * Configure the max number of application attempt retries.
|
|
|
+
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+|| Property || Description |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+| <<<yarn.resourcemanager.am.max-attempts>>> | |
|
|
|
+| | The maximum number of application attempts. It's a global |
|
|
|
+| | setting for all application masters. Each application master can specify |
|
|
|
+| | its individual maximum number of application attempts via the API, but the |
|
|
|
+| | individual number cannot be more than the global upper bound. If it is, |
|
|
|
+| | the RM will override it. The default number is set to 2, to |
|
|
|
+| | allow at least one retry for AM. |
|
|
|
+*--------------------------------------+--------------------------------------+
|
|
|
+
|
|
|
+ This configuration's impact is in fact beyond RM restart scope. It controls
|
|
|
+ the max number of attempts an application can have. In RM Restart Phase 1,
|
|
|
+ this configuration is needed since as described earlier each time RM restarts,
|
|
|
+ it kills the previously running attempt (i.e. ApplicationMaster) and
|
|
|
+ creates a new attempt. Therefore, each occurrence of RM restart causes the
|
|
|
+ attempt count to increase by 1. In RM Restart phase 2, this configuration is not
|
|
|
+ needed since the previously running ApplicationMaster will
|
|
|
+ not be killed and the AM will just re-sync back with RM after RM restarts.
|
Jian He