WARN Executor: 2 block locks were not released by TID =
Lock release errors occur frequently in executor logs
原因：If there are any releasedLocks (after calling BlockManager.releaseAllLocksForTask earlier) and spark.storage.exceptionOnPinLeak is enabled (it is not by default) with no exception having been thrown while the task was running, a SparkException is thrown:
[releasedLocks] block locks were not released by TID = [taskId]:
[releasedLocks separated by comma]
Otherwise, if spark.storage.exceptionOnPinLeak is disabled or an exception was thrown by the task, the following WARN message is displayed in the logs instead:
WARN Executor: [releasedLocks] block locks were not released by TID = [taskId]:
[releasedLocks separated by comma]
Note If there are any releaseLocks, they lead to a SparkException or WARN message in the logs.
[jaceklaskowski/mastering-apache-spark-book/spark-executor-taskrunner.adoc]
mapWithState causes block lock warning?
The warning was added by: SPARK-12757 Add block-level read/write locks to BlockManager?
[connectedComponents() raises lots of warnings that say "block locks were not released by TID = ..."]
[Lock release errors occur frequently in executor logs]
解决：终于在调试log时候发现问题解决了
在简略Spark输出设置时[Spark安装和配置]修改过$SPARK_HOME/conf/log4j.properties.template文件只输出WARN信息，就算改成了ERROR，信息也还是会自动修改成WARN输出出来，不过多了一条提示：
Setting default log level to "WARN". To adjust logging level use sc.setLogLevel(newLevel).
就在这时发现了一个解决方案：
根据提示在代码中加入sc.setLogLevel('ERROR')就可以解决了！
from: http://blog.csdn.net/pipisorry/article/details/52916307
ref:
