rpc: tighter shutdown synchronization in client subscription #22597
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This fixes a rare issue where the client subscription forwarding loop
would attempt send on the subscription's channel after Unsubscribe has
returned, leading to a panic if the subscription channel was already
closed by the user. Example:
sub, _ := client.Subscribe(..., channel, ...)
sub.Unsubscribe()
close(channel)
The race occurred because Unsubscribe called quitWithServer to tell the
forwarding loop to stop sending, but did not wait for the loop to
actually stop. This is fixed by adding an additional channel to track
the shutdown, on which Unsubscribe now waits.
Not sure why this was there, but it's useless: when forward exits, the list is no longer referenced and doesn't need to be cleared.
The mockup server in this test can't handle the method call.
holiman
approved these changes
Mar 30, 2021
|
Amazing, thank you! |
atif-konasl
pushed a commit
to frozeman/pandora-execution-engine
that referenced
this pull request
Oct 15, 2021
…m#22597) This fixes a rare issue where the client subscription forwarding loop would attempt send on the subscription's channel after Unsubscribe has returned, leading to a panic if the subscription channel was already closed by the user. Example: sub, _ := client.Subscribe(..., channel, ...) sub.Unsubscribe() close(channel) The race occurred because Unsubscribe called quitWithServer to tell the forwarding loop to stop sending on sub.channel, but did not wait for the loop to actually come down. This is fixed by adding an additional channel to track the shutdown, on which Unsubscribe now waits. Fixes ethereum#22322
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This was referenced Sep 23, 2022
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This fixes a rare issue where the client subscription forwarding loop
would attempt send on the subscription's channel after Unsubscribe has
returned, leading to a panic if the subscription channel was already
closed by the user. Example:
The race occurred because Unsubscribe called quitWithServer to tell the
forwarding loop to stop sending on sub.channel, but did not wait for the
loop to actually come down. This is fixed by adding an additional channel
to track the shutdown, on which Unsubscribe now waits.
Fixes #22322