Standalone模式下，通過Systemd管理Flink1.11.1的啟停及異常退出
Flink以Standalone模式運行時，可能會發生jobmanager（以下簡稱jm）或taskmanager（以下簡稱tm）異常退出的情況，我們可以使用Linux自帶的Systemd方式管理jm以及tm的啟停，並在jm或tm出現故障時，及時將jm以及tm拉起來。
Flink在1.11版本後，從發行版中移除了對Hadoop的依賴包，如果需要使用Hadoop的一些特性，有兩種解決方案：
【注】以下假設java、flink、hadoop都安裝在/opt目錄下，並且都建立了軟連接：
1.設置HADOOP_CLASSPATH環境變量（推薦方案）
在安裝了Flink的所有節點上，在/etc/profile中進行如下設置：
# Hadoop Env
export HADOOP_HOME=/opt/hadoop
export PATH=$PATH:$HADOOP_HOME/bin:$HADOOP_HOME/sbin
export HADOOP_CLASSPATH=`hadoop classpath`
然後通過以下命令使環境變量生效
sudo source /etc/profile
2.下載flink-shaded-hadoop-2-uber對應的jar包，並拷貝到Flink安裝路徑的lib目錄下
下載地址：//flink.apache.org/downloads.html#additional-components
由於以systemd方式啟動時，系統設置的環境變量，在.service文件中是不能使用的，所以需要在.service文件中單獨顯式設置環境變量：
1./usr/lib/systemd/system/flink-jobmanager.service
[Unit] Description=Flink Job Manager After=syslog.target network.target remote-fs.target nss-lookup.target network-online.target Requires=network-online.target [Service] User=teld Group=teld Type=forking Environment=PATH=/opt/java/bin:/opt/flink/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin Environment=JAVA_HOME=/opt/java Environment=FLINK_HOME=/opt/flink Environment=HADOOP_CLASSPATH=/opt/hadoop/etc/hadoop:/opt/hadoop/share/hadoop/common/lib/*:/opt/hadoop/share/hadoop/common/*:/opt/hadoop/ share/hadoop/hdfs:/opt/hadoop/share/hadoop/hdfs/lib/*:/opt/hadoop/share/hadoop/hdfs/*:/opt/hadoop/share/hadoop/yarn/lib/*:/opt/hadoop/sh are/hadoop/yarn/*:/opt/hadoop/share/hadoop/mapreduce/lib/*:/opt/hadoop/share/hadoop/mapreduce/*:/opt/hadoop/contrib/capacity-scheduler/* .jar ExecStart=/opt/flink/bin/jobmanager.sh start ExecStop=/opt/flink/bin/jobmanager.sh stop Restart=on-failure [Install] WantedBy=multi-user.target
【注】HADOOP_CLASSPATH對應的值，是通過執行以下命令獲得到的：
hadoop classpath
2./usr/lib/systemd/system/flink-taskmanager.service
[Unit] Description=Flink Task Manager After=syslog.target network.target remote-fs.target nss-lookup.target network-online.target Requires=network-online.target [Service] User=teld Group=teld Type=forking Environment=PATH=/opt/java/bin:/opt/flink/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin Environment=JAVA_HOME=/opt/java Environment=FLINK_HOME=/opt/flink Environment=HADOOP_CLASSPATH=/opt/hadoop/etc/hadoop:/opt/hadoop/share/hadoop/common/lib/*:/opt/hadoop/share/hadoop/common/*:/opt/hadoop/ share/hadoop/hdfs:/opt/hadoop/share/hadoop/hdfs/lib/*:/opt/hadoop/share/hadoop/hdfs/*:/opt/hadoop/share/hadoop/yarn/lib/*:/opt/hadoop/sh are/hadoop/yarn/*:/opt/hadoop/share/hadoop/mapreduce/lib/*:/opt/hadoop/share/hadoop/mapreduce/*:/opt/hadoop/contrib/capacity-scheduler/* .jar ExecStart=/opt/flink/bin/taskmanager.sh start ExecStop=/opt/flink/bin/taskmanager.sh stop Restart=on-failure [Install] WantedBy=multi-user.target
【注】HADOOP_CLASSPATH對應的值，是通過執行以下命令獲得到的：
hadoop classpath
通過sudo systemctl daemon-reload命令來加載上面針對jm以及tm的配置後，就可以使用Systemd的方式來管理jm以及tm了，並且能夠在jm以及tm異常退出時，及時將它們拉起來：
sudo systemctl start flink-jobmanager.service
sudo systemctl stop flink-jobmanager.service
sudo systemctl status flink-jobmanager.service
sudo systemctl start flink-taskmanager.service
sudo systemctl stop flink-taskmanager.service
sudo systemctl status flink-jobmanager.service
遇到的坑：
1.如果Flink設置了啟用Checkpoint，但是沒有設置HADOOP_CLASSPATH環境變量，則提交job的時候，會報如下異常：
Caused by: org.apache.flink.util.FlinkRuntimeException: Failed to create checkpoint storage at checkpoint coordinator side. at org.apache.flink.runtime.checkpoint.CheckpointCoordinator.<init>(CheckpointCoordinator.java:304) at org.apache.flink.runtime.checkpoint.CheckpointCoordinator.<init>(CheckpointCoordinator.java:223) at org.apache.flink.runtime.executiongraph.ExecutionGraph.enableCheckpointing(ExecutionGraph.java:483) at org.apache.flink.runtime.executiongraph.ExecutionGraphBuilder.buildGraph(ExecutionGraphBuilder.java:338) at org.apache.flink.runtime.scheduler.SchedulerBase.createExecutionGraph(SchedulerBase.java:269) at org.apache.flink.runtime.scheduler.SchedulerBase.createAndRestoreExecutionGraph(SchedulerBase.java:242) at org.apache.flink.runtime.scheduler.SchedulerBase.<init>(SchedulerBase.java:229) at org.apache.flink.runtime.scheduler.DefaultScheduler.<init>(DefaultScheduler.java:119) at org.apache.flink.runtime.scheduler.DefaultSchedulerFactory.createInstance(DefaultSchedulerFactory.java:103) at org.apache.flink.runtime.jobmaster.JobMaster.createScheduler(JobMaster.java:284) at org.apache.flink.runtime.jobmaster.JobMaster.<init>(JobMaster.java:272) at org.apache.flink.runtime.jobmaster.factories.DefaultJobMasterServiceFactory.createJobMasterService(DefaultJobMasterServiceFac tory.java:98) at org.apache.flink.runtime.jobmaster.factories.DefaultJobMasterServiceFactory.createJobMasterService(DefaultJobMasterServiceFac tory.java:40) at org.apache.flink.runtime.jobmaster.JobManagerRunnerImpl.<init>(JobManagerRunnerImpl.java:140) at org.apache.flink.runtime.dispatcher.DefaultJobManagerRunnerFactory.createJobManagerRunner(DefaultJobManagerRunnerFactory.java :84) at org.apache.flink.runtime.dispatcher.Dispatcher.lambda$createJobManagerRunner$6(Dispatcher.java:388) ... 7 more Caused by: org.apache.flink.core.fs.UnsupportedFileSystemSchemeException: Could not find a file system implementation for scheme 'hdfs'. The scheme is not directly supported by Flink and no Hadoop file system to support this scheme could be loaded. For a full list of supp
2.在為flink-jobmanager.service以及flink-taskmanager.service中的HADOOP_CLASSPATH環境變量賦值時，嘗試使用過反引號，期望將反引號內的Linux命令執行結果賦予變量，但實際上並不會執行反引號中的內容：
Environment=HADOOP_CLASSPATH=`/opt/hadoop/bin/hadoop classpath`
最後只得將直接執行hadoop classpath獲得的結果，粘貼到.service文件中
Environment=HADOOP_CLASSPATH=/opt/hadoop/etc/hadoop:/opt/hadoop/share/hadoop/common/lib/*:/opt/hadoop/share/hadoop/common/*:/opt/hadoop/ share/hadoop/hdfs:/opt/hadoop/share/hadoop/hdfs/lib/*:/opt/hadoop/share/hadoop/hdfs/*:/opt/hadoop/share/hadoop/yarn/lib/*:/opt/hadoop/sh are/hadoop/yarn/*:/opt/hadoop/share/hadoop/mapreduce/lib/*:/opt/hadoop/share/hadoop/mapreduce/*:/opt/hadoop/contrib/capacity-scheduler/* .jar
