在Flink上启动 yarn-session.sh时出现 The number of requested virtual cores for application master 1 exceeds the maximum number of virtual cores 0 available in the Yarn Cluster.错误。

版本说明：

Hadoop： 3.3.4

Flink：1.17.1

问题

在Flink On Yarn上启动yarn-session.sh时出现如下错误：

ERROR org.apache.flink.yarn.cli.FlinkYarnSessionCli        [] - Error while running the Flink session.org.apache.flink.client.deployment.ClusterDeploymentException: Couldn't deploy Yarn session cluster
​	at org.apache.flink.yarn.YarnClusterDescriptor.deploySessionCluster(YarnClusterDescriptor.java:437) ~[flink-dist-1.17.1.jar:1.17.1]
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.run(FlinkYarnSessionCli.java:608) ~[flink-dist-1.17.1.jar:1.17.1]
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.lambda$main$4(FlinkYarnSessionCli.java:869) ~[flink-dist-1.17.1.jar:1.17.1]
​	at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_231]
​	at javax.security.auth.Subject.doAs(Subject.java:422) ~[?:1.8.0_231]
​	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1878) ~[hadoop-common-3.3.4.jar:?]
​	at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41) ~[flink-dist-1.17.1.jar:1.17.1]
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.main(FlinkYarnSessionCli.java:869) [flink-dist-1.17.1.jar:1.17.1]
Caused by: org.apache.flink.configuration.IllegalConfigurationException: The number of requested virtual cores for application master 1 exceeds the maximum number of virtual cores 0 available in the Yarn Cluster.
​	at org.apache.flink.yarn.YarnClusterDescriptor.isReadyForDeployment(YarnClusterDescriptor.java:338) ~[flink-dist-1.17.1.jar:1.17.1]
​	at org.apache.flink.yarn.YarnClusterDescriptor.deployInternal(YarnClusterDescriptor.java:567) ~[flink-dist-1.17.1.jar:1.17.1]
​	at org.apache.flink.yarn.YarnClusterDescriptor.deploySessionCluster(YarnClusterDescriptor.java:430) ~[flink-dist-1.17.1.jar:1.17.1]
​	... 7 more
------------------------------------------------------------The program finished with the following exception:
org.apache.flink.client.deployment.ClusterDeploymentException: Couldn't deploy Yarn session cluster
​	at org.apache.flink.yarn.YarnClusterDescriptor.deploySessionCluster(YarnClusterDescriptor.java:437)
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.run(FlinkYarnSessionCli.java:608)
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.lambda$main$4(FlinkYarnSessionCli.java:869)
​	at java.security.AccessController.doPrivileged(Native Method)
​	at javax.security.auth.Subject.doAs(Subject.java:422)
​	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1878)
​	at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41)
​	at org.apache.flink.yarn.cli.FlinkYarnSessionCli.main(FlinkYarnSessionCli.java:869)
Caused by: org.apache.flink.configuration.IllegalConfigurationException: The number of requested virtual cores for application master 1 exceeds the maximum number of virtual cores 0 available in the Yarn Cluster.
​	at org.apache.flink.yarn.YarnClusterDescriptor.isReadyForDeployment(YarnClusterDescriptor.java:338)
​	at org.apache.flink.yarn.YarnClusterDescriptor.deployInternal(YarnClusterDescriptor.java:567)
​	at org.apache.flink.yarn.YarnClusterDescriptor.deploySessionCluster(YarnClusterDescriptor.java:430)
​	... 7 more

原因

在yarn-site.xml文件中配置了所有可能相关的参数，重启yarn服务，执行yarn-session.sh错误依旧：

	<property><name>yarn.containers.vcores</name><value>8</value></property><property><name>yarn.nodemanager.resource.cpu-vcores</name><value>4</value></property><property><name>yarn.scheduler.maximum-allocation-vcores</name><value>2</value></property>

在看yarn cluster上的信息时突然发现Unhealth Nodes，然后查看了具体信息：

具体原因就是磁盘使用空间占比超过了90了（yarn默认为90），则认为不健康，不健康相当于这个节点不可用，由于本地只有一个节点，所以相当于整个集群不可用，于是就出现了开头的错误信息。

解决

根据Health-report的提示，在yarn-site.xml中添加了如下参数：

	<property><name>yarn.nodemanager.disk-health-checker.max-disk-utilization-per-disk-percentage</name><value>99</value></property>

重启yarn，再查看节点状态为正常了，再执行flink的yarn-session.sh就可以正常启动了。

总结

在Flink中使用yarn-session时，如果出现yarn相关的错误，可以到Yarn的WebUI上查看可能的Unhealth-report和具体的错误信息，再根据具体信息调整配置后不断调试，直到解决问题。