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https://issues.apache.org/jira/browse/BOOKKEEPER-101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13150621#comment-13150621
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[email protected] commented on BOOKKEEPER-101:
----------------------------------------------------------



bq.  On 2011-11-15 07:18:20, Dhruba Borthakur wrote:
bq.  > 
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/Bookie.java, line 
583
bq.  > <https://reviews.apache.org/r/2594/diff/4/?file=57330#file57330line583>
bq.  >
bq.  >     Just a minor nit: maybe rename addEntryToLedger to 
addEntryInternal() just to distinguish public methods from private methods. No 
big deal anyways!

Changed.


bq.  On 2011-11-15 07:18:20, Dhruba Borthakur wrote:
bq.  > 
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/Bookie.java, line 
602
bq.  > <https://reviews.apache.org/r/2594/diff/4/?file=57330#file57330line602>
bq.  >
bq.  >     This is called when a client is trying to do recovery. In this case, 
should this call first assert that the fenced flag is already set in the 
handle? something like:
bq.  >     
bq.  >     if (!handle.isFeenced()) {
bq.  >       throw Exception()
bq.  >     }

we don't always fence the ledger before recovery. In the case of bookie 
recovery, we want to replicate all active ledgers to ensure full replication. 
Some may be open, some may be. In this case we use a recovery add, to ensure we 
can add. All adds will be of entries read from the same ledger, on another 
bookie.


bq.  On 2011-11-15 07:18:20, Dhruba Borthakur wrote:
bq.  > 
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/Bookie.java, line 
639
bq.  > <https://reviews.apache.org/r/2594/diff/4/?file=57330#file57330line639>
bq.  >
bq.  >     I like this simple api to fence. Maybe the javadoc can specify that 
even if the handle is already fenced, invoking this api is ok and keeps the 
fencing flag still set.

Added.


bq.  On 2011-11-15 07:18:20, Dhruba Borthakur wrote:
bq.  > 
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/Bookie.java, line 
642
bq.  > <https://reviews.apache.org/r/2594/diff/4/?file=57330#file57330line642>
bq.  >
bq.  >     A handle, once fenced, can never be set to an 'unfenced' state, am I 
correct?

Yes, fencing is permanent.  


- Ivan


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On 2011-11-10 11:14:47, Ivan Kelly wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/2594/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-11-10 11:14:47)
bq.  
bq.  
bq.  Review request for bookkeeper.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  BookKeeper is designed for use as a Write ahead log. In systems with a 
primary/backup architecture, the primary will write state updates to the WAL. 
If the primary dies the backup comes online, reads the WAL to get the latest 
state and starts serving requests. However, if the primary was only partitioned 
from the network, or stuck in a long GC, a split brain occurs. Both primary and 
backup can service client requests.
bq.  
bq.  Fencing(http://en.wikipedia.org/wiki/Fencing_%28computing%29) ensures that 
this cannot happen. With fencing, the backup can close the WAL of the primary, 
and cause any subsequent attempt by the primary to write to the WAL to give an 
error.
bq.  
bq.  
bq.  This addresses bug BOOKKEEPER-101.
bq.      https://issues.apache.org/jira/browse/BOOKKEEPER-101
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/Bookie.java 
d651894 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieException.java
 292617e 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/LedgerDescriptor.java
 024cac3 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/BKException.java 
d7c8f67 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/BookKeeper.java 
a1fbab7 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/BookKeeperAdmin.java
 b3eb5b9 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerCreateOp.java
 6f72e47 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandle.java 
8c2a54f 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadata.java
 328c7ca 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerOpenOp.java 
a68856c 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerRecoveryOp.java
 7465c52 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingAddOp.java 
eddd760 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingReadOp.java 
385b16c 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadLastConfirmedOp.java
 c2d4cee 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadOnlyLedgerHandle.java
 PRE-CREATION 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieClient.java 
d70ae27 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieProtocol.java 
873dafe 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieServer.java 
f1b3ad9 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/NIOServerFactory.java
 e0743bb 
bq.    
bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java
 2cd4de8 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestFencing.java 
PRE-CREATION 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/proto/TestProtoVersions.java
 f6cd8c9 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/test/BaseTestCase.java 
6bac569 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/test/BookieClientTest.java
 97dc2ab 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/test/BookieRecoveryTest.java
 ac54d9a 
bq.    
bookkeeper-server/src/test/java/org/apache/bookkeeper/test/LoopbackClient.java 
85822bf 
bq.    
hedwig-server/src/main/java/org/apache/hedwig/server/benchmark/BookieBenchmark.java
 18319d7 
bq.  
bq.  Diff: https://reviews.apache.org/r/2594/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Ivan
bq.  
bq.


                
> Add Fencing to Bookkeeper
> -------------------------
>
>                 Key: BOOKKEEPER-101
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-101
>             Project: Bookkeeper
>          Issue Type: New Feature
>            Reporter: Ivan Kelly
>            Assignee: Ivan Kelly
>             Fix For: 4.0.0
>
>         Attachments: BOOKKEEPER-101.diff, BOOKKEEPER-101.diff, 
> BOOKKEEPER-101.diff, BOOKKEEPER-101.diff
>
>
> BookKeeper is designed for use as a Write ahead log. In systems with a 
> primary/backup architecture, the primary will write state updates to the WAL. 
> If the primary dies the backup comes online, reads the WAL to get the latest 
> state and starts serving requests. However, if the primary was only 
> partitioned from the network, or stuck in a long GC, a split brain occurs. 
> Both primary and backup can service client requests. 
> Fencing(http://en.wikipedia.org/wiki/Fencing_%28computing%29) ensures that 
> this cannot happen. With fencing, the backup can close the WAL of the 
> primary, and cause any subsequent attempt by the primary to write to the WAL 
> to give an error. 
> We fence a ledger whenever it is opened by another client using 
> BookKeeper#openLedger. BookKeeper#openLedgerNoRecovery will not fence.
> The opening client marks the ledger as fenced in zookeeper, and then sends a 
> readEntry message to a all of bookies with the DO_FENCING flag set. Once at 
> least 1 bookie in each possible quorum of bookies have responded, we can 
> proceed with opening the ledger. Any subsequent attempt to write to the 
> ledger will fail as it will not be able to write to a quorum without one of 
> the bookie in the quorum responding with a ledger fenced error. The client 
> will also be unable to change the quorum without seeing that the ledger has 
> been marked as fenced in zookeeper.

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