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https://issues.apache.org/jira/browse/FLUME-1085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13259708#comment-13259708
 ] 

[email protected] commented on FLUME-1085:
------------------------------------------------------



bq.  On 2012-04-19 09:12:40, Arvind Prabhakar wrote:
bq.  > Thanks for the patch Brock. The implementation looks great to me! Some 
feedback follows:
bq.  > 
bq.  > Some convention nits:
bq.  > * Please make sure the line lengths are under 80 chars.
bq.  > * Please use all caps for variables that are static final.
bq.  > 
bq.  > One high-level consideration: Since it is possible to have multiple file 
channels within the same agent, we should either make file channel multi-tenant 
capable like the jdbc channel, or instead have the ability to associate 
directory locks for the file channel instance for checkpoint and data 
directories. Doing this will ensure that there is no corruption and the system 
exits cleanly in case of misconfiguration.
bq.  > 
bq.  > If you chose to implement the non-multitenant system, it will be 
preferable to use the channel name within the default paths for checkpoint and 
data directories. This will ensure minimum configuration necessary even when 
using multiple file channels within the same agent.
bq.  > 
bq.  >
bq.  
bq.  Brock Noland wrote:
bq.      I added locks to ensure only one channel has access to the directories 
at a given time.
bq.      
bq.      This is a concern I have a about JDBC Channel. I am not sold on using 
the channel name from the configuration as that is a symbolic name, users will 
likely think they can change it. However, if there are events stored in that 
channel and they change the name, all their events are gone. If we used the 
name this same thing would occur. Today with JDBC Channel and this 
implementation of FileChannel, it can be multi-tenant if configured to use 
different directories for each Channel. I feel like this is a better approach.
bq.      
bq.      Thoughts?
bq.  
bq.  Arvind Prabhakar wrote:
bq.      For JDBC channel, this is a necessary evil. If the channel was not 
multi-tenant capable, it would mean a new connection pool, statement caches, 
cursors, etc for every channel instance. In which case the agent would become 
extremely resource heavy and would require extensive configuration to work out 
of the box. So instead we chose to use the channel name to disambiguate. I 
agree that this needs to be clearly documented and that users should know that 
the events will be lost if they change the channel name. The good news is that 
this is recoverable and even manually fixable.
bq.      
bq.      Since the file channel does not suffer from similare heavy resource 
requirements, it is good to have locks to ensure there is no corruption; even 
though that means that for an agent only one channel instance can exist with 
default configuration.

Makes sense to me.


- Brock


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On 2012-04-19 20:10:53, Brock Noland wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/4661/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2012-04-19 20:10:53)
bq.  
bq.  
bq.  Review request for Flume.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  This patch implements a durable file channel. It does by writing all 
transaction events to disk and syncing to disk when a commit occurs. It does 
have a memory component in that pointers to the event on disk are kept in 
memory. This will consume 8 bytes of direct memory (non-heap) per event. Some 
basic calculations are in the FileChannel java docs.
bq.  
bq.  
bq.  This addresses bug FLUME-1085.
bq.      https://issues.apache.org/jira/browse/FLUME-1085
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    flume-ng-channels/flume-file-channel/pom.xml e8155be 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Checkpoint.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Commit.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/FileChannel.java
 a279453 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/FileChannelConfiguration.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/FlumeEvent.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/FlumeEventPointer.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/FlumeEventQueue.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Log.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/LogFile.java
 PRE-CREATION 
bq.    
flume-ng-sdk/src/test/java/org/apache/flume/api/TestNettyAvroRpcClient.java 
0b8a2c0 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/LogUtils.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Pair.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Put.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/ReplayHandler.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Rollback.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/Take.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/main/java/org/apache/flume/channel/file/TransactionEventRecord.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/CountingSinkRunner.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/CountingSourceRunner.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestCheckpoint.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestFileChannel.java
 ab66998 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestFlumeEvent.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestFlumeEventPointer.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestFlumeEventQueue.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestLog.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestLogFile.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestTransactionEventRecord.java
 PRE-CREATION 
bq.    
flume-ng-channels/flume-file-channel/src/test/java/org/apache/flume/channel/file/TestUtils.java
 PRE-CREATION 
bq.    flume-ng-channels/flume-file-channel/src/test/resources/log4j.properties 
739ecc8 
bq.    
flume-ng-channels/flume-recoverable-memory-channel/src/main/java/org/apache/flume/channel/recoverable/memory/RecoverableMemoryChannel.java
 0622f27 
bq.    
flume-ng-channels/flume-recoverable-memory-channel/src/main/java/org/apache/flume/channel/recoverable/memory/wal/SequenceIDBuffer.java
 fa63b73 
bq.    
flume-ng-core/src/main/java/org/apache/flume/channel/ChannelProcessor.java 
eb6460e 
bq.    flume-ng-core/src/main/java/org/apache/flume/channel/ChannelType.java 
d8419e8 
bq.    flume-ng-core/src/main/java/org/apache/flume/sink/NullSink.java c812851 
bq.    flume-ng-core/src/main/java/org/apache/flume/source/StressSource.java 
PRE-CREATION 
bq.    
flume-ng-core/src/main/java/org/apache/flume/tools/DirectMemoryUtils.java 
PRE-CREATION 
bq.    
flume-ng-sdk/src/test/java/org/apache/flume/api/TestFailoverRpcClient.java 
225cd34 
bq.  
bq.  Diff: https://reviews.apache.org/r/4661/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  Unit tests and integration tests added to cover obvious cases.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Brock
bq.  
bq.


                
> Implement a durable FileChannel
> -------------------------------
>
>                 Key: FLUME-1085
>                 URL: https://issues.apache.org/jira/browse/FLUME-1085
>             Project: Flume
>          Issue Type: New Feature
>          Components: Channel
>    Affects Versions: v1.2.0
>            Reporter: Brock Noland
>            Assignee: Brock Noland
>
> FLUME-896 turned into a durable Memory Channel, we need a durable File Channel

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