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Postfix Documentation
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Example 3: Congestion in the active queue

This example is taken from a Feb 2004 discussion on the Postfix Users list. Congestion was reported with the active and incoming queues large and not shrinking despite very large delivery agent process limits. The thread is archived at:

Using an older version of qshape(1) it was quickly determined that all the messages were for just a few destinations:

$ qshape        (show 
incoming and 
active queue status)

                           T   A   5  10  20  40  80 160 320 320+
                 TOTAL 11775 9996  0   0   1   1  42  94 221 1420  7678 7678  0   0   0   0   0   0   0    0  2313 2313  0   0   0   0   0   0   0    0   102    0  0   0   0   0   0   0   2  100

The "A" column showed the count of messages in the active queue, and the numbered columns showed totals for the deferred queue. At 10000 messages (Postfix 1.x active queue size limit) the active queue is full. The incoming was growing rapidly.

With the trouble destinations clearly identified, the administrator quickly found and fixed the problem. It is substantially harder to glean the same information from the logs. While a careful reading of mailq(1) output should yield similar results, it is much harder to gauge the magnitude of the problem by looking at the queue one message at a time.

Postfix Documentation
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