flink-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From StephanEwen <...@git.apache.org>
Subject [GitHub] flink pull request: [wip] [FLINK-2288] [FLINK-2302] Setup ZooKeepe...
Date Tue, 07 Jul 2015 12:55:50 GMT
Github user StephanEwen commented on a diff in the pull request:

    --- Diff: docs/setup/jobmanager_high_availability.md ---
    @@ -0,0 +1,121 @@
    +title: "JobManager High Availability (HA)"
    +Licensed to the Apache Software Foundation (ASF) under one
    +or more contributor license agreements.  See the NOTICE file
    +distributed with this work for additional information
    +regarding copyright ownership.  The ASF licenses this file
    +to you 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
    +KIND, either express or implied.  See the License for the
    +specific language governing permissions and limitations
    +under the License.
    +The JobManager is the coordinator of each Flink deployment. It is responsible for both
*scheduling* and *resource management*.
    +By default, there is a single JobManager instance per Flink cluster. This creates a *single
point of failure* (SPOF): if the JobManager crashes, no new programs can be submitted and
running programs fail.
    +With JobManager High Availability, you can run multiple JobManager instances per Flink
cluster and thereby circumvent the *SPOF*.
    +The general idea of JobManager high availability is that there is a **single leading
JobManager** at any time and **multiple standby JobManagers** to take over leadership in case
the leader fails. This guarantees that there is **no single point of failure** and programs
can make progress as soon as a standby JobManager has taken leadership. There is no explicit
distinction between standby and master JobManager instances. Each JobManager can take the
role of master or standby.
    +As an example, consider the following setup with three JobManager instances:
    +<img src="fig/jobmanager_ha_overview.png" class="center" />
    +## Configuration
    +To enable JobManager High Availability you have to configure a **ZooKeeper quorum** and
set up a **masters file** with all JobManagers hosts.
    +Flink leverages **[ZooKeeper](http://zookeeper.apache.org)** for  *distributed coordination*
between all running JobManager instances. ZooKeeper is a separate service from Flink, which
provides highly reliable distirbuted coordination via leader election and light-weight consistent
state storage. Check out [ZooKeeper's Getting Started Guide](http://zookeeper.apache.org/doc/trunk/zookeeperStarted.html)
for more information about ZooKeeper.
    +Configuring a ZooKeeper quorum in `conf/flink-conf.yaml` *enables* high availability
mode and all Flink components try to connect to a JobManager via coordination through ZooKeeper.
    +- **ZooKeeper quorum** (required): A *ZooKeeper quorum* is a replicated group of ZooKeeper
servers, which provide the distributed coordination service.
    +  <pre>ha.zookeeper.quorum: address1:2181[,...],addressX:2181</pre>
    +  Each *addressX:port* refers to a ZooKeeper server, which is reachable by Flink at the
given address and port.
    +- The following configuration keys are optional:
    +  - `ha.zookeeper.dir: /flink [default]`: ZooKeeper directory to use for coordination
    +  - TODO Add client configuration keys
    +## Starting an HA-cluster
    +In order to start an HA-cluster configure the *masters* file in `conf/masters`:
    +- **masters file**: The *masters file* contains all hosts, on which JobManagers are started.
    +  <pre>
    +  </pre>
    +After configuring the masters and the ZooKeeper quorum, you can use the provided cluster
startup scripts as usual. They will start a HA-cluster. **Keep in mind that the ZooKeeper
quorum has to be running when you call the scripts**.
    +## Running ZooKeeper
    +If you don't have a running ZooKeeper installation, you can use the helper scripts, which
ship with Flink.
    +There is a ZooKeeper configuration template in `conf/zoo.cfg`. You can configure the
hosts to run ZooKeeper on with the `server.X` entries, where X is a unique ID of each server:
    +The script `bin/start-zookeeper-quorum.sh` will start a ZooKeeper server on each of the
configured hosts. The started processes start ZooKeeper servers via a Flink wrapper, which
reads the configuration from `conf/zoo.cfg` and makes sure to set some rqeuired configuration
values for convenience. In production setups, it is recommended to manage your own ZooKeeper
    --- End diff --
    Typo: `rqeuired` -> `required`

If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastructure@apache.org or file a JIRA ticket
with INFRA.

View raw message