如何修改Namenode侦测错误Datanode的时间

最新推荐文章于 2023-07-31 22:34:27 发布

矮胖挫

最新推荐文章于 2023-07-31 22:34:27 发布

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分类专栏： hadoop 文章标签： extension constants hadoop testing socket

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本文介绍了如何在Hadoop 0.19版本中通过调整心跳参数来更快地检测失败的DataNode节点，包括heartbeat.recheck.interval等关键配置，并解释了这些参数对集群稳定性的影响。

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A question was asked of me recently, on how to force the namenode to detect failed datanodes more quickly.

This is very useful when testing, and can be quite risky on busy clusters.
In hadoop 19, the parameter heartbeat.recheck.interval is the primary control.
This value, in msec, is just under 1/2 of the timeout period for a Datanode.

In hadoop 0.19, in FSNamesystem.java:

long heartbeatInterval = conf.getLong("dfs.heartbeat.interval", 3) * 1000; / 3 seconds
this.heartbeatRecheckInterval = conf.getInt( "heartbeat.recheck.interval", 5 * 60 * 1000); // 5 minutes
this.heartbeatExpireInterval = 2 * heartbeatRecheckInterval + 10 * heartbeatInterval;

To change the timeout at your client/application level, the parameter
this.socketTimeout = conf.getInt(" dfs.socket.timeout ",
HdfsConstants.READ_TIMEOUT);
this.datanodeWriteTimeout = conf.getInt(" dfs.datanode.socket.write.timeout ",
HdfsConstants.WRITE_TIMEOUT);

dfs.socket.timeout controls the base timeout for read/connect operations against a datanode.

The constants are:
// Timeouts for communicating with DataNode for streaming writes/reads
public static int READ_TIMEOUT = 60 * 1000;
public static int WRITE_TIMEOUT = 8 * 60 * 1000;
public static int WRITE_TIMEOUT_EXTENSION = 5 * 1000; //for write pipeline

The write timeout for an individual dfs write operation is defined as
long writeTimeout = HdfsConstants.WRITE_TIMEOUT_EXTENSION * nodes.length +
datanodeWriteTimeout;
or 40 minutes times the replication factor.

The socket timeout for a dfs operation is defined as:
int timeoutValue = 3000 * nodes.length + socketTimeout;
which is roughly the replication factor times 3 minutes.