[ 
https://forge.continuent.org/jira/browse/SEQUOIA-1150?page=comments#action_15567
 ] 

Emmanuel Cecchet commented on SEQUOIA-1150:
-------------------------------------------

The LogCommitEvent code already takes care of read-only transactions, there is 
no need to do that in logCommit.
Replace:

  public long logCommit(TransactionMetaData tm)
  {
    if (tm.isReadOnly())
    {
      // don't log commit, if trx is read only
      return 0;
    }
    else
    {
      long id = incrementLogTableId();
      loggerThread.log(new LogCommitEvent(new LogEntry(id, tm.getLogin(),
          COMMIT, null, LogEntry.TRANSACTION, tm.getTransactionId())));
      tm.setLogId(id);
      return id;
    }
  }

with 

  public long logCommit(TransactionMetaData tm)
  {
      long id = incrementLogTableId();
      loggerThread.log(new LogCommitEvent(new LogEntry(id, tm.getLogin(),
          COMMIT, null, LogEntry.TRANSACTION, tm.getTransactionId())));
      tm.setLogId(id);
      return id;
  }

Keep me posted if that fixes the issue.

> SELECT  ... FOR UPDATE with no actual UPDATE prevents backend recovery
> ----------------------------------------------------------------------
>
>          Key: SEQUOIA-1150
>          URL: https://forge.continuent.org/jira/browse/SEQUOIA-1150
>      Project: Sequoia
>         Type: Bug

>   Components: Recovery Log
>     Versions: sequoia 2.10.10
>  Environment: Discovered on Centos 5 with MySQL 5.1 for backends and 
> Controller
> Single controller configuration
>     Reporter: Joel Kozikowski
>     Assignee: Emmanuel Cecchet
>     Priority: Critical
>  Attachments: TestSequoiaSelectForUpdate.java
>
>
> If the following sequence is issued to the database:
> 1) Start transaction
> 2) SELECT * WHERE ID = 1234 FOR UPDATE
> 3) End transaction
> 4) <zero or more other queries>
> 5) Start transaction
> 6) SELECT * WHERE ID = 1234 FOR UPDATE
> 7) End transaction
> The following gets written to the recovery log:
> 1) BEGIN (transaction n)
> 2) SELECT * WHERE ID = 1234 FOR UPDATE (transaction n)
> 3) BEGIN (transaction n+1)
> 4) SELECT * WHERE ID = 1234 FOR UPDATE (transaction n+1)
> The absense of a "COMMIT" in the recovery log causes ""Lock wait timeout 
> exceeded; try restarting transaction"
>  in MySQL when played back (because two seprate transactions are trying to 
> lock the same record, but never release the locks).

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