We track the number of messages in each postfix queue on our mailservers using a program I've written. For most queues, it simply does a readdir() and counts all files whose names don't begin with ".", which is quick and efficient. For the deferred queue, it does a find-style walk through the directory tree. Unfortunately, on our fallback relays the deferred queues can get very large, and walking the tree becomes a long and expensive endeavor.
By far the largest amount of time and I/O is spent calling stat() on hundreds of thousands of queue files to determing that they're simple files rather than directories to descend into. I could avoid that two ways: 1. If I could tell simply from the filename whether it's a queue file or a subdirectory: for example, if the name is 3 characters or longer it's a queue file, shorter than 3 it's a directory. 2. If the tree structure were static enough that I could make assumptions about it: for example, every file in the top level is a subdirectory, every file in a subdirectory is a queue file. I can look at what I've got and extrapolate rules like the above, but I don't know whether postfix *might* do something differently later on that I just haven't seen, and I don't know whether the "rule" I'm using will apply to other versions of postfix. Are there any solid rules I can use to avoid calling stat on everything when counting the deferred queue and any other hierarchical queues postfix may have in current and future versions? -- Cos
