fix: deadlock when reloading configs #398
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This manifested in k8s because we get double notified about config changes. Previously, onChange would acquire a read lock, and then each callback would also acquire a read lock when reading whatever config value they care about. onChange also acquires a write lock when unmarshalling. With additional goroutines calling onChange (e.g. in k8s), we were almost guaranteed to have a write lock in between two recursive read locks. From Go RLock docs: // It should not be used for recursive read locking; a blocked Lock // call excludes new readers from acquiring the lock. See the // documentation on the RWMutex type. Removing the read lock around callbacks - every config accessor function already has a read lock.
vreynolds
added
type: bug
MikeGoldsmith
approved these changes
Feb 10, 2022
seh
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Feb 10, 2022
ghost
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Jul 5, 2024
This manifested in k8s because we get double notified about config changes. Previously, onChange would acquire a read lock, and then each callback would also acquire a read lock when reading whatever config value they care about. onChange also acquires a write lock when unmarshalling. With additional goroutines calling onChange (e.g. in k8s), we were almost guaranteed to have a write lock in between two recursive read locks. From Go RLock docs: // It should not be used for recursive read locking; a blocked Lock // call excludes new readers from acquiring the lock. See the // documentation on the RWMutex type. Removing the read lock around callbacks - every config accessor function already has a read lock.
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Which problem is this PR solving?
This manifested in k8s because we get double notified about config changes.
Previously, onChange would acquire a read lock, and then each callback would also acquire a read lock
when reading whatever config value they care about. onChange also acquires a write lock when unmarshalling.
With additional goroutines calling onChange (e.g. in k8s), we were almost guaranteed to have a write lock in
between two recursive read locks.
From Go RLock docs:
A helpful answer from StackOverflow: https://stackoverflow.com/a/30549188
Fixes #380
Short description of the changes
Removing the read lock around callbacks. Every config accessor function already has a read lock, and we don't care about locking config if a callback doesn't read config values.