[Mailman-Users] Mail going to list archives but not to list!

[Barry Warsaw]

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On Sep 26, 2006, at 2:12 PM, Brad Knowles wrote:

> At 8:51 AM -0400 9/26/06, Elizabeth Schwartz wrote:
>
>>  Another question:  is there any parallelism of processing files  
>> in the out
>>  queue or are they done sequentially?
>
> By default, it's single-threaded -- but not really "sequential".  It
> has more to do with how the directory entries are written, and not
> what you or I would think of as "sequential".
>
> There are ways to get more than one Outgoing queue runner working,
> but that's a very non-standard configuration, and takes more work to
> maintain.  I would like to see Mailman move towards a hashed queue
> mechanism (like postfix), so that it would be a lot easier to have
> multiple Outgoing queue runners working at the same time.

Actually, Mailman does implement a hashed queue of sorts for its  
queue runners.  Every queue file is assigned a hash and a timestamp,  
encoded in the file name.  The timestamp is so that qrunners can  
handle the files in FIFO order.  The hash creates a "hash space" for  
when multiple qrunners are used per queue.  In that case, each  
qrunner is responsible for a slice of the hash space, so that they  
can run concurrently without having to deal with expensive and tricky  
locks.

Multiple qrunners are a supported configuration, although I believe  
their use is rare.  In fact, qrunners can contend for list locks  
which can reduce their concurrency, but the OutgoingRunner is one  
place where write access to the list data isn't necessary and care  
was taken so that multiple OutgoingRunners could maximize their  
concurrency.

(fyi: there is an end-case bug in the hash space algorithm in Mailman  
pre-2.1.9.  I don't think anyone's ever hit it, but Mark found it  
through visual inspection of the code.  Fixed in 2.1.9.)

Cheers,
- -Barry

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