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https://issues.apache.org/jira/browse/HDDS-1397?focusedWorklogId=225135&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-225135
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ASF GitHub Bot logged work on HDDS-1397:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 09/Apr/19 16:36
            Start Date: 09/Apr/19 16:36
    Worklog Time Spent: 10m 
      Work Description: hanishakoneru commented on issue #701: HDDS-1397. Avoid 
the usage of signal handlers in datanodes of the MiniOzoneClusters
URL: https://github.com/apache/hadoop/pull/701#issuecomment-481327506
 
 
   Thanks @elek for fixing this. LGTM. +1.
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 225135)
    Time Spent: 50m  (was: 40m)

> Avoid the usage of signal handlers in datanodes of the MiniOzoneClusters
> ------------------------------------------------------------------------
>
>                 Key: HDDS-1397
>                 URL: https://issues.apache.org/jira/browse/HDDS-1397
>             Project: Hadoop Distributed Data Store
>          Issue Type: Bug
>            Reporter: Elek, Marton
>            Assignee: Elek, Marton
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 50m
>  Remaining Estimate: 0h
>
> [~arpaga] showed me a problem that TestQueryNode.testHealthyNodesCount is 
> failed in the CI check of HDDS-1339.
> According to the logs the test is timed out because only 4 datanodes are 
> started out of the 5.
> The log also contained an exception from one datanode:
> {code}
> 2019-04-04 00:26:33,583 WARN  ozone.HddsDatanodeService 
> (LogAdapter.java:warn(59)) - failed to register any UNIX signal loggers: 
> java.lang.IllegalStateException: Can't re-install the signal handlers.
>     at org.apache.hadoop.util.SignalLogger.register(SignalLogger.java:77)
>     at 
> org.apache.hadoop.util.StringUtils.startupShutdownMessage(StringUtils.java:718)
>     at 
> org.apache.hadoop.util.StringUtils.startupShutdownMessage(StringUtils.java:707)
>     at 
> org.apache.hadoop.ozone.HddsDatanodeService.createHddsDatanodeService(HddsDatanodeService.java:126)
>     at 
> org.apache.hadoop.ozone.HddsDatanodeService.createHddsDatanodeService(HddsDatanodeService.java:108)
>     at 
> org.apache.hadoop.ozone.MiniOzoneClusterImpl$Builder.createHddsDatanodes(MiniOzoneClusterImpl.java:552)
> {code}
> The code which requires the signal handler is the following (signal handler 
> is registered in the startupShutdownMessage)
> {code}
>   /**
>    * Create an Datanode instance based on the supplied command-line arguments.
>    * <p>
>    * This method is intended for unit tests only. It suppresses the
>    * startup/shutdown message and skips registering Unix signal handlers.
>    *
>    * @param args        command line arguments.
>    * @param conf        HDDS configuration
>    * @param printBanner if true, then log a verbose startup message.
>    * @return Datanode instance
>    */
>   private static HddsDatanodeService createHddsDatanodeService(
>       String[] args, Configuration conf, boolean printBanner) {
>     if (args.length == 0 && printBanner) {
>       StringUtils
>           .startupShutdownMessage(HddsDatanodeService.class, args, LOG);
>       return new HddsDatanodeService(conf);
>     } else {
>       new HddsDatanodeService().run(args);
>       return null;
>    }
> {code}
> As you can read from the comment it's expected to be called with 
> printBanner=false to avoid the creation of the signal handler. 
> Note: In the startupShutdownMessage method a new signal handler is registered 
> and signal handlers can be registered only once:
> {code}
> //SignalLogger
>   void register(final LogAdapter LOG) {
>    if (registered) {
>       throw new IllegalStateException("Can't re-install the signal 
> handlers.");
>     }
>  ....
> {code}
> We have a dedicated method to create datanode service for the unit tests. The 
> only thing what we need is to turn OFF the signal handler registration here. 
> (The following code fragment shows the original state where the signal 
> handler creation is requested with the true parameter value)
> {code}
>   @VisibleForTesting
>   public static HddsDatanodeService createHddsDatanodeService(
>       String[] args, Configuration conf) {
>     return createHddsDatanodeService(args, conf, true);
>   }
> {code}



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