ZooKeeper High availability ZooKeeper is the foundation of the HDFS automatic

Zookeeper high availability zookeeper is the

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ZooKeeper High availability ZooKeeper is the foundation of the HDFS automatic failover feature. ZooKeeper provides a highly available service for maintaining coordination data, notifying clients of changes in that data, and monitoring clients for failures. For more information, see HDFS Automatic Failover . To run the following applications in an EMR cluster with multiple master nodes, you must configure an external database. The external database exists outside the cluster and makes data persistent during the master node failover process. For the following applications, the service components will automatically recover during the master node failover process, but active jobs may fail and need to be retried. Application Availability during master node failover Notes Hive High availability for service components only An external metastore for Hive is required. For more information, see Configuring an External Metastore for Hive . Hue High availability for service components only An external database for Hue is required. For more information, see Using Hue with a Remote Database in Amazon RDS . Oozie High availability for service components only An external database for Oozie is required. For more information, see Using Oozie with a Remote Database in Amazon RDS . Oozie-server is installed on only one master node, while oozie-client is installed on all three master nodes. The oozie-clients are configured to connect to the correct oozie-server by default. You can find the private DNS name of the master node where oozie-server is installed by checking the variable OOZIE_URL on any master node in the file /etc/oozie/conf.dist/oozie-client- env.sh . Presto High availability for service components only An external Hive metastore for Presto is required. You can use Presto with the AWS Gule Data Catalog or use an External MySQL Database for Hive . 57
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Amazon EMR Management Guide Supported Applications and Features Note When a master node fails, your Java Database Connectivity (JDBC) or Open Database Connectivity (ODBC) terminates its connection to the master node. You can connect to any of the remaining master nodes to continue your work because the Hive metastore daemon runs on all master nodes. Or you can wait for the failed master node to be replaced. How EMR Features work in a Cluster with Multiple Master Nodes Connecting to Master Nodes Using SSH You can connect to any of the three master nodes in an EMR cluster using SSH in the same way you connect to a single master node. For more information, see Connect to the Master Node Using SSH . If a master node fails, your SSH connection to that master node ends. To continue your work, you can connect to one of the other two master nodes. Alternatively, you can access the new master node after EMR replaces the failed one with a new one.
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  • Spring '12
  • LauraParker
  • Amazon Web Services, Amazon Elastic Compute Cloud

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