#265: Failure when fetching a file with wget
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Reporter: toots | Owner: admin
Type: Bugs | Status: new
Priority: 8 | Milestone: NEAR FUTURE
Component: Liquidsoap | Version: 0.9.0+svn
Resolution: | Keywords:
Mac: 1 | Linux: 1
Netbsd: 1 | Other: 1
Freebsd: 1 |
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Comment(by mrpingouin):
I was responsible for that code, I should comment it. For now, let me
explain it here.
You want to wait for a process, but no longer than {{{timeout}}} seconds.
The solution uses {{{select}}} to wait no longer than expected. We create
a pipe {{{(xR,xW)}}}, don't do anything with the input end, and wait for
something to read on the output end: it never happens, except when the
pipe is closed, i.e. the process terminated. Indeed, the pipe {{{xW}}} is
still open in the child process, until it dies. If the select terminates
because of the timeout, we get empty lists, and we kill the process. Then
we can {{{wait}}} for it, it's almost instantaneous.
The other pipe is a fresh one created for the stdin of the new process,
just to avoid that it reads on liquidsoap's stdin.
I like the idea of that solution. It does requires some non-trivial
knowledge of unix, but it avoids a waiting loop.
Now, the error that you got is raised by the {{{Unix.close xW}}}, and it's
{{{EBADF}}}. The protocol resolvers are supposed to fail cleanly, without
raising, so we should catch it. Still, I'm a bit surprised that it
happened, we must be having an exotic situation here: as you said, this
code dates back before 0.3.0 and never caused any problem. It is typical
to close unused ends of a pipe, and I don't see how the descriptor freshly
created could be invalid and not closable...
--
Ticket URL: <http://savonet.rastageeks.org/ticket/265#comment:2>
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