(PUP-11897) Fix excessive cpu usage after EOF from an exec #9105
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When EOF is reached, calls to IO.select() will return immediately, resulting in puppet executing the loop without any internal blocking. This causes up to 100% usage of a CPU core until the child finishes. If the child does its own stdout/stderr redirection before a long operation, for example, this can result in much wasted CPU usage. There is no need to execute the body of the loop after EOF is reached, so switch the Process.waitpid2 flags to block.
This adds testing for 4f35fd2 which fixes excessive core usage when an exec has received an EOF.
With the change in 4f35fd2, the execution tests need to have mocked out the an addtional call to `waitpid2` that has the flag set to zero.
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joshcooper
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Sep 11, 2023
| @@ -235,6 +239,7 @@ def self.execute(command, options = NoOptionsSpecified) | |||
| output << reader.read_nonblock(4096) if ready | |||
| rescue Errno::EAGAIN | |||
| rescue EOFError | |||
| wait_flags &= ~Process::WNOHANG | |||
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Masking off WNOHANG would make sense if something modified the variable between the time it was initialized to wait_flags = Process::WNOHANG and here. For example, if wait_flags was an in-and-out parameter in the call to Process.waitpid2. But since the variable isn't modified and the default value for the flags parameter is 0 (i.e. Process.waitpid2(pid, flags = 0)), then I think it'd be clearer to set this to wait_flags = 0.
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Superseded by #9106 which will be merged up to main later. |
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