[ZODB-Dev] "Transaction blocked waiting for storage"

[Jim Fulton]

On Jun 22, 2009, at 11:06 AM, Andreas Jung wrote:

> On 22.06.09 16:56, Pedro Ferreira wrote:
>> Hello all,
>> We occasionally get some messages like this in the logs:
>>
>> 2009-06-22T14:12:42 (30651/137.138.128.213:35787) Transaction blocked
>> waiting for storage. Clients waiting: 1.
>>
>> But today we eventually got to:
>>
>> 2009-06-22T16:00:11 (30651/137.138.4.153:53416) Transaction blocked
>> waiting for storage. Clients waiting: 204.
>>
>> Which lasted some minutes.  During that time, our system seemed to  
>> hang,
>> even if it was possible to connect to the db through the command  
>> line.
>> It eventually went back to normal by itself.
>> Any clue on what might have caused this?
> The reason is likely a long running transaction. Since the storage  
> server
> is single-threaded, a long running transaction will block pending  
> requests.


No, the storage server is only blocked in the very last stage of a two- 
phase commit, not for the entire duration of the transaction.

Jim

--
Jim Fulton
Zope Corporation