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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5485) Remove WebServer dependency on DrillClient
Date Wed, 24 May 2017 07:04:04 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16022417#comment-16022417
] 

ASF GitHub Bot commented on DRILL-5485:
---------------------------------------

Github user sohami commented on a diff in the pull request:

    https://github.com/apache/drill/pull/829#discussion_r118160625
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/rpc/AbstractUserClientConnectionWrapper.java
---
    @@ -0,0 +1,101 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *    http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.drill.exec.rpc;
    +
    +import com.google.common.base.Preconditions;
    +import org.apache.drill.common.exceptions.UserException;
    +import org.apache.drill.common.exceptions.UserRemoteException;
    +import org.apache.drill.exec.proto.GeneralRPCProtos;
    +import org.apache.drill.exec.proto.UserBitShared.DrillPBError;
    +import org.apache.drill.exec.proto.UserBitShared.QueryId;
    +import org.apache.drill.exec.proto.UserBitShared.QueryResult;
    +import org.apache.drill.exec.proto.helper.QueryIdHelper;
    +
    +import java.util.concurrent.CountDownLatch;
    +import java.util.concurrent.TimeUnit;
    +
    +public abstract class AbstractUserClientConnectionWrapper implements UserClientConnection
{
    +  private static final org.slf4j.Logger logger =
    +      org.slf4j.LoggerFactory.getLogger(AbstractUserClientConnectionWrapper.class);
    +
    +  protected final CountDownLatch latch = new CountDownLatch(1);
    +
    +  protected volatile DrillPBError error;
    +
    +  protected volatile UserException exception;
    +
    +  /**
    +   * Wait until the query has completed or timeout is passed.
    +   *
    +   * @throws InterruptedException
    +   */
    +  public boolean await(final long timeoutMillis) throws InterruptedException {
    +    return latch.await(timeoutMillis, TimeUnit.MILLISECONDS);
    +  }
    +
    +  /**
    +   * Wait indefinitely until the query is completed. Used only in case of WebUser
    +   *
    +   * @throws Exception
    +   */
    +  public void await() throws Exception {
    +    latch.await();
    +    if (exception != null) {
    +      throw exception;
    +    }
    +  }
    +
    +  @Override
    +  public void sendResult(RpcOutcomeListener<GeneralRPCProtos.Ack> listener, QueryResult
result) {
    +
    +    Preconditions.checkState(result.hasQueryState());
    +
    +    // Release the wait latch if the query is terminated.
    +    final QueryResult.QueryState state = result.getQueryState();
    +    final QueryId queryId = result.getQueryId();
    +
    +    if (logger.isDebugEnabled()) {
    +      logger.debug("Result arrived for QueryId: {} with QueryState: {}", QueryIdHelper.getQueryId(queryId),
state);
    +    }
    +
    +    switch (state) {
    +      case FAILED:
    +        error = result.getError(0);
    +        exception = new UserRemoteException(error);
    +        latch.countDown();
    +        break;
    +      case CANCELED:
    +      case COMPLETED:
    +        Preconditions.checkState(result.getErrorCount() == 0);
    +        latch.countDown();
    +        break;
    +      default:
    +        logger.error("Query with QueryId: {} is in unexpected state: {}", queryId, state);
    --- End diff --
    
    In [DrillClient](https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/rpc/user/QueryResultHandler.java#L134)
we just log and ignore any invalid QueryState. Looks like client always expect a valid state
to be reported for the query ?


> Remove WebServer dependency on DrillClient
> ------------------------------------------
>
>                 Key: DRILL-5485
>                 URL: https://issues.apache.org/jira/browse/DRILL-5485
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Web Server
>            Reporter: Sorabh Hamirwasia
>             Fix For: 1.11.0
>
>
> With encryption support using SASL, client's won't be able to authenticate using PLAIN
mechanism when encryption is enabled on the cluster. Today WebServer which is embedded inside
Drillbit creates a DrillClient instance for each WebClient session. And the WebUser is authenticated
as part of authentication between DrillClient instance and Drillbit using PLAIN mechanism.
But with encryption enabled this will fail since encryption doesn't support authentication
using PLAN mechanism, hence no WebClient can connect to a Drillbit. There are below issues
as well with this approach:
> 1) Since DrillClient is used per WebUser session this is expensive as it has heavyweight
RPC layer for DrillClient and all it's dependencies. 
> 2) If the Foreman for a WebUser is also selected to be a different node then there will
be extra hop of transferring data back to WebClient.
> To resolve all the above issue it would be better to authenticate the WebUser locally
using the Drillbit on which WebServer is running without creating DrillClient instance. We
can use the local PAMAuthenticator to authenticate the user. After authentication is successful
the local Drillbit can also serve as the Foreman for all the queries submitted by WebUser.
This can be achieved by submitting the query to the local Drillbit Foreman work queue. This
will also remove the requirement to encrypt the channel opened between WebServer (DrillClient)
and selected Drillbit since with this approach there won't be any physical channel opened
between them.



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