Using Zookeeper
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Using Zookeeper
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Available in VPC
Data Forest provides Apache Zookeeper servers. Zookeeper is a distributed coordination system that helps coordinating distributed application tasks. It contains zk-web to allow viewing and manipulating znodes via a web UI.
Check Zookeeper app details
When the app creation is completed, you can view the details. When the Status is Stable under the app's details, it means the app is running normally.
The following describes how to check the app details.
- From the NAVER Cloud Platform console, click the Services > Big Data & Analytics > Data Forest > App menus, in that order.
- Select the account that owns the app.
- Click the app whose details you want to view.
- View the app details.
- Quick links: endpoints shown by the components of the app
- AppMaster: URL where the container log can be viewed When creating apps, all apps are submitted to the YARN queue. YARN provides a web UI where each app's details can be viewed.
- zkweb-ui: After logging in to the web UI, you can set the Zookeeper path in the format of
zkserver-0.app name.service account.cluster domain:2181/.
- Components: The value specified by default is the recommended resource.
- zkweb: Run zk-web.
- zkserver: Run Zookeeper.
- Quick links: endpoints shown by the components of the app
Note
- When creating the Zookeeper app, the zkweb component is fixed at 1 and zkserver component is fixed at 3 under Configuration > Number of containers.
- Refer to Access quick links for information on how to log in to the AppMaster UI and view the logs of each container.
Example
The following is the zkweb UI screen after connection.
If the login is successful, then you can see the znode information as shown below.
Link Zookeeper with other apps
The Zookeeper app can be linked with the Apache HBase, Apache Kafka, and OpenTSDB apps. If you want to use the HBase, Kafka, or OpenTSDB app, then you must create the Zookeeper app first.
Check container's host name
When you create an app, the host names of its containers are automatically specified.
The number of containers for the zkserver component is specified to be 3, which is the default value.
If a user called "test" runs ZOOKEEPER-3.4.13 that has a zkserver component with the app name "zookeeper," then the 3 containers executed would have host names as follows.
- zkserver-0.zookeeper.test.kr.df.naverncp.com
- zkserver-1.zookeeper.test.kr.df.naverncp.com
- zkserver-2.zookeeper.test.kr.df.naverncp.com
Configure Zookeeper app from HBase app
If you want to run the Apache HBase app, then you must create the Zookeeper app first.
Set Zookeeper to be used in HBase as hbase-site's hbase.zookeeper.quorum. Set it as the container of the Zookeeper app created. For more detailed information, refer to the Apache HBase Reference Guide.
Precautions for using the Zookeeper app
Change the number of zkservers
The address of the server to be added has to be included in the settings of the server that is already running. It not easy to change the number of zkserver containers without stopping the server. It is recommended to start the app with an appropriate number of servers if possible. At the moment, the number of zkserver containers is fixed to 3. A feature for adjusting the number of zkserver containers is scheduled be added later.
Note
If you've changed Configuration > Number of containers, then you should add (or delete) the server.X configuration to /conf/zoo.cfg under Files, according to the number you changed it to. In addition, the env file's DNS_REGISTRY_CHECK_HOSTS settings need to be configured according to the number changed.
Zookeeper data retention
- The Zookeeper app's data (dataDir) created by the user is saved in Data Forest's local file system, and it is not deleted unless the user destroys the app.
- If the YARN queue has enough resources, then the container will run on the same node, even if the user stops and restarts the Zookeeper app, and be able to read the znode data from the previous session.
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