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https://issues.apache.org/jira/browse/HADOOP-17975?focusedWorklogId=681239&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-681239
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ASF GitHub Bot logged work on HADOOP-17975:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 14/Nov/21 15:37
Start Date: 14/Nov/21 15:37
Worklog Time Spent: 10m
Work Description: fapifta opened a new pull request #3658:
URL: https://github.com/apache/hadoop/pull/3658
### Description of PR
In the JIRA there is a long description about the problem, the TLDR is that
if there are two DFSClient instance at the same time on the client side, the
second one can not properly fall back to SIMPLE auth due to how the
SaslRpcClient handles the fallback via an AtomicBoolean created by the
DfsClient, and set by the hadoop.ipc.Client.
The initial idea/solution was posted as #3579 where we had a long discussion
with @symious about this solution and that solution, and the tradeoffs. After a
while, I think I was convinced that this is a proper solution, and fits into
the current system, so I am adding this PR to finally fix the issue.
The solution is to add the AtomicBoolean fallbackToSimpleAuth which controls
how/if the SaslRpcClient falls back to simple auth or not, to the ConnectionId
class, and with that distinguish the connections of the two DfsClient based on
the fallbackToSimpleAuth AtomicBoolean instance. If that is different, from any
other connections' AtomicBoolean instance, then we will distinguish the
connection, and with that we will initialize the value of fallbackToSimpleAuth
properly.
### How was this patch tested?
JUnit test added.
The problem manifested itself as a failing HBase ExportSnapshot job, between
two small clusters, one using Kerberos auth one using Simple auth. With this
fix the ExportSnapshot job was able to run as well.
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Issue Time Tracking
-------------------
Worklog Id: (was: 681239)
Time Spent: 6h 20m (was: 6h 10m)
> Fallback to simple auth does not work for a secondary DistributedFileSystem
> instance
> ------------------------------------------------------------------------------------
>
> Key: HADOOP-17975
> URL: https://issues.apache.org/jira/browse/HADOOP-17975
> Project: Hadoop Common
> Issue Type: Bug
> Components: ipc
> Reporter: István Fajth
> Assignee: István Fajth
> Priority: Major
> Labels: pull-request-available
> Time Spent: 6h 20m
> Remaining Estimate: 0h
>
> The following code snippet demonstrates what is necessary to cause a failure
> in connection to a non secure cluster with fallback to SIMPLE auth allowed
> from a secure cluster.
> {code:java}
> Configuration conf = new Configuration();
> conf.setBoolean("ipc.client.fallback-to-simple-auth-allowed", true);
> URI fsUri = new URI("hdfs://<nn_uri>");
> conf.setBoolean("fs.hdfs.impl.disable.cache", true);
> FileSystem fs = FileSystem.get(fsUri, conf);
> FSDataInputStream src = fs.open(new Path("/path/to/a/file"));
> FileOutputStream dst = new FileOutputStream(File.createTempFile("foo",
> "bar"));
> IOUtils.copyBytes(src, dst, 1024);
> // The issue happens even if we re-enable cache at this point
> //conf.setBoolean("fs.hdfs.impl.disable.cache", false);
> // The issue does not happen when we close the first FileSystem object
> // before creating the second.
> //fs.close();
> FileSystem fs2 = FileSystem.get(fsUri, conf);
> FSDataInputStream src2 = fs2.open(new Path("/path/to/a/file"));
> FileOutputStream dst2 = new FileOutputStream(File.createTempFile("foo",
> "bar"));
> IOUtils.copyBytes(src2, dst2, 1024);
> {code}
> The problem is that when the DfsClient is created it creates an instance of
> AtomicBoolean, which is propagated down into the IPC layer, where the
> Client.Connection instance in setupIOStreams sets its value. This connection
> object is cached and re-used to multiplex requests against the same DataNode.
> In case of creating a second DfsClient, the AtomicBoolean reference in the
> client is a new AtomicBoolean, but the Client.Connection instance is the
> same, and as it has a socket already open to the DataNode, it returns
> immediatelly from setupIOStreams, leaving the fallbackToSimpleAuth
> AtomicBoolean false as it is created in the DfsClient.
> This AtomicBoolean on the other hand controls how the SaslDataTransferClient
> handles the connection in the above level, and with this value left on the
> default false, the SaslDataTransferClient of the second DfsClient will not
> fall back to SIMPLE authentication but will try to send a SASL handshake when
> connecting to the DataNode.
>
> The access to the FileSystem via the second DfsClient fails with exceptions
> like the following one, then fails the read with a BlockMissingException like
> below:
> {code}
> WARN hdfs.DFSClient: Failed to connect to /<dn_ip>:<dn_port> for file <file>
> for block BP-531773307-<nn_ip>-1634685133591:blk_1073741826_1002, add to
> deadNodes and continue.
> java.io.EOFException: Unexpected EOF while trying to read response from server
> at
> org.apache.hadoop.hdfs.protocolPB.PBHelperClient.vintPrefixed(PBHelperClient.java:552)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.DataTransferSaslUtil.readSaslMessage(DataTransferSaslUtil.java:215)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient.doSaslHandshake(SaslDataTransferClient.java:455)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient.getSaslStreams(SaslDataTransferClient.java:393)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient.send(SaslDataTransferClient.java:267)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient.checkTrustAndSend(SaslDataTransferClient.java:215)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferClient.peerSend(SaslDataTransferClient.java:160)
> at
> org.apache.hadoop.hdfs.DFSUtilClient.peerFromSocketAndKey(DFSUtilClient.java:648)
> at
> org.apache.hadoop.hdfs.DFSClient.newConnectedPeer(DFSClient.java:2980)
> at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.nextTcpPeer(BlockReaderFactory.java:822)
> at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:747)
> at
> org.apache.hadoop.hdfs.client.impl.BlockReaderFactory.build(BlockReaderFactory.java:380)
> at
> org.apache.hadoop.hdfs.DFSInputStream.getBlockReader(DFSInputStream.java:658)
> at
> org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:589)
> at
> org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:771)
> at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:840)
> at java.io.DataInputStream.read(DataInputStream.java:100)
> at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:94)
> at DfsClientTest3.main(DfsClientTest3.java:30)
> {code}
> {code}
> org.apache.hadoop.hdfs.BlockMissingException: Could not obtain block:
> BP-813026743-<nn_ip>-1495248833293:blk_1139767762_66027405 file=/path/to/file
> {code}
>
> The DataNode in the meantime logs the following:
> {code}
> ERROR org.apache.hadoop.hdfs.server.datanode.DataNode:
> <dn_host>:<dn_port>:DataXceiver error processing unknown operation src:
> /<client_ip>:<client_port> dst: /<dn_ip>:<dn_port>
> java.io.IOException: Version Mismatch (Expected: 28, Received: -8531 )
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.readOp(Receiver.java:70)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:222)
> at java.lang.Thread.run(Thread.java:748)
> {code}
> This happens only if the second client is connecting to the same DataNode as
> the first one did, so might seem intermittent in case the clients are reading
> different files, but happens always if the two client reads the same file
> with replication factor 1.
> We ran into this issue during running HBase ExportSnapshot tool to move a
> snapshot from a non-secure to a secure cluster, the issue is loosely related
> to HBASE-12819 and HBASE-20433 and similar problems, I am linking these so
> that HBase team will see how this is relevant for them.
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