Do not inherit open FDs to SQLite worker by overwriting and closing #7
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This somewhat obscure PR ensures that we do not inherit open file descriptors (FDs) to the SQLite child worker process. This can cause all sorts of errors in long running applications and really is not desired here. This is implemented by explicitly overwriting all superfluous FDs with dummy file handles and then closing all of these in the implicit `sh` child process before launching the actual php binary. PHP does not support `FD_CLOEXEC`, `O_CLOEXEC` or `SOCK_CLOEXEC` and this appears to be the best work around I could find (yes, I should probably write a lengthy, somewhat technical blog post about this). Additionally, this PR includes a test to verify this works on all supported platforms and this could perhaps be used as a starting point for other libraries (YMMV). This builds on top of clue/reactphp-ssh-proxy#2 and clue/reactphp-ssh-proxy#10
clue
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May 3, 2019
There's a very short race condition where the forked php process first has to `dup()` the file descriptor specs before invoking `exec()` to switch to the actual `ssh` child process. We don't need to wait for the child process to be ready, but only for the forked process to close the file descriptors. This happens ~80% of times on single core machines and almost never on multi core systems, so simply wait 5ms (plenty of time!) and retry again. Builds on top of clue#7
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This somewhat obscure PR ensures that we do not inherit open file
descriptors (FDs) to the SQLite child worker process. This can cause all
sorts of errors in long running applications and really is not desired
here.
This is implemented by explicitly overwriting all superfluous FDs with
dummy file handles and then closing all of these in the implicit
shchild process before launching the actual php binary. PHP does not
support
FD_CLOEXEC,O_CLOEXECorSOCK_CLOEXECand this appears tobe the best work around I could find (yes, I should probably write a
lengthy, somewhat technical blog post about this). Additionally, this PR
includes a test to verify this works on all supported platforms and this
could perhaps be used as a starting point for other libraries (YMMV).
This builds on top of clue/reactphp-ssh-proxy#2
and clue/reactphp-ssh-proxy#10
Refs reactphp/child-process#51