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72 lines
3.3 KiB
Plaintext
72 lines
3.3 KiB
Plaintext
These are a list of recurrent bugs in Supybot, and ways to notice
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them. It just might come in useful for people maintaining code.
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1. Using == or != when you mean ircutils.strEqual. Nicks, prefixes,
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and channels should be compared for equality not by == or !=, but
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by ircutils.strEqual. This does a case-normalized check. Don't
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just use lower() because that doesn't use the rfc1459 casemapping.
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To find:
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grep == plugins/*.py | egrep "nick|channel"
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grep "!=" plugins/*.py | egrep "nick|channel"
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2. Using a warning log when it really should be an info log. Users
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don't like to see warnings. If we have warning logs, they'll
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complain. So let's try to make them complain as little as
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possible, and only use warnings when you've encountered a *very*
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odd situation, or when you need more information before
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determining if something is correct.
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An example: The Services plugin has two methods, doNickservNotice
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and doChanservNotice, which doNotice dispatches to appropriately.
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Now, we can't possibly predict all the possible messages that
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ChanServ or NickServ might send to us. So I put a default clause
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in there that just says, "Hey, this is an unexpected message from
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ChanServ/NickServ: ..." I log this at warning level because I
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want to know when there's a NickServ/ChanServ message I haven't
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seen before. This works: the warning makes users report it.
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Another example: We used to log failures in snarfers at the
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warning level. But do the users really want to be warned when a
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given "url" isn't valid? No! So now we just make it an info log,
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so that users who care can still see why a snarfer didn't snarf,
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but no one complains to us about it.
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To find:
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grep log.warning plugins/*.py
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3. Spelling errors. They plague almost every large piece of
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software. Supybot is no different, but we have a weapon against
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them: find-strings.py. Give find-strings.py a set of files, and
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it'll extract all the non-raw literal strings from the source code
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and output them to a file, with the originating file, line number,
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and string. Spell-checking Supybot is just a matter of taking
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this 10,000 line file and an hour and running aspell over it,
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correcting the errors in the original file as you find them.
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To find:
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find-strings.py src/*.py plugins/*.py scripts/supybot*
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4. Pegging the CPU. It has happened in the past that bugs in Supybot
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have caused 100% CPU usage. These are insidious, and generally
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hard to track down. Here are our tools against them; we assuming
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that the bug is reproducible.
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First, I load the Debug plugin and settrace to a file, then I
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quickly reproduce the bug, and let the CPU spin for awhile. Then
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I kill the bot and check the trace file (which should be large).
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I look for patterns that would indicate an infinite loop of some
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sort.
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Second, I strace the bot when it's looping. If I see output, it's
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making syscalls; if I don't see any output, it's not. If it's
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making syscalls, that might mean it's looping in the network
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drivers somehow; if not, it's somewhere else.
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Third, I check that no regexps could be causing it. They're
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notorious for appearing safe, but actually hiding exponential
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complexity code (the kind of code that strong cryptography is
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based on).
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After that, I pray harder :)
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