replacer: use RWMutex to protect static provider #6184
Merged
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I received a report of concurrent map-write crash. When the the executable was built with the race detector, the following stacktrace is produced.
It points at the
Replacer
. It might be the case on high traffic, theSet
on replacer in the reverse proxy handling here is accessed concurrently and upsets the runtime:caddy/modules/caddyhttp/reverseproxy/reverseproxy.go
Lines 430 to 434 in c37e16f
This might have risen due to reverse-proxy, cache, and probably other handler that spinoff goroutines may indeed cause concurrent map access. This might've slipped through the cracks because most other handlers don't spinoff goroutines and the concurrent request just didn't happen to cross this threshold.