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From sohami <...@git.apache.org>
Subject [GitHub] drill pull request #679: DRILL-5098: Improving fault tolerance for connectio...
Date Wed, 14 Dec 2016 00:10:38 GMT
Github user sohami commented on a diff in the pull request:

    https://github.com/apache/drill/pull/679#discussion_r92296665
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/client/DrillClient.java ---
    @@ -357,10 +357,53 @@ protected void afterExecute(final Runnable r, final Throwable t)
{
             super.afterExecute(r, t);
           }
         };
    -    client = new UserClient(clientName, config, supportComplexTypes, allocator, eventLoopGroup,
executor);
    -    logger.debug("Connecting to server {}:{}", endpoint.getAddress(), endpoint.getUserPort());
    -    connect(endpoint);
    -    connected = true;
    +
    +    // "tries" is max number of unique drillbit to try connecting until successfully
connected to one of them
    +    final String connectTriesConf = (props != null) ? props.getProperty("tries", "5")
: "5";
    +
    +    int connectTriesVal;
    +    try {
    +      connectTriesVal = Math.min(endpoints.size(), Integer.parseInt(connectTriesConf));
    +    } catch (NumberFormatException e) {
    +      throw new InvalidConnectionInfoException("Invalid tries value: " + connectTriesConf
+ " specified in " +
    +                                               "connection string");
    +    }
    +
    +    // If the value provided in the connection string is <=0 then override with 1
since we want to try connecting
    +    // at least once
    +    connectTriesVal = Math.max(1, connectTriesVal);
    +
    +    int triedEndpointIndex = 0;
    +    DrillbitEndpoint endpoint;
    +
    +    while (triedEndpointIndex < connectTriesVal) {
    +      client = new UserClient(clientName, config, supportComplexTypes, allocator, eventLoopGroup,
executor);
    +      endpoint = endpoints.get(triedEndpointIndex);
    +      logger.debug("Connecting to server {}:{}", endpoint.getAddress(), endpoint.getUserPort());
    +
    +      try {
    +        connect(endpoint);
    +        connected = true;
    +        logger.info("Successfully connected to server {}:{}", endpoint.getAddress(),
endpoint.getUserPort());
    +        break;
    +      } catch (InvalidConnectionInfoException ex) {
    +        logger.error("Connection to {}:{} failed with error {}. Not retrying anymore",
endpoint.getAddress(),
    +                     endpoint.getUserPort(), ex.getMessage());
    +        throw ex;
    +      } catch (RpcException ex) {
    +        ++triedEndpointIndex;
    +        logger.error("Attempt {}: Failed to connect to server {}:{}", triedEndpointIndex,
endpoint.getAddress(),
    +                     endpoint.getUserPort());
    +
    +        // Close the connection
    +        client.close();
    --- End diff --
    
    I didn't found anywhere in documentation specifying the cause of calling close multiple
times. It just says that internally close is being called for each handler in the pipeline.
https://netty.io/4.0/api/io/netty/channel/Channel.html#close()
    
    Though I do have unit tests which will result in covering that code path where close will
be called twice. Didn't found any issue running the test. 


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