Avoid panic on concurrent writes to cached service config map #10647
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Alternatively we could use different cache keys for each requesting proxy: consul/agent/service_manager.go Line 205 in 832896e Rather than relying on the default: consul/agent/structs/config_entry.go Line 645 in 832896e This would lead to having a separate entry in the cache for each proxy. |
If multiple instances of a service are co-located on the same node then their proxies will all share a cache entry for their resolved service configuration. This is because the cache key contains the name of the watched service but does not take into account the ID of the watching proxies. This means that there will be multiple agent service manager watches that can wake up on the same cache update. These watchers then concurrently modified the value in the cache when merging the resolved config into the local proxy definitions. To avoid this concurrent map write we will only delete the key from opaque config from the local proxy definition after the merge, rather than from the cached value before the merge. Fixes #10636
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Nice! Change LGTM. Thinking about how to test this, I guess trying to reproduce the panic would be difficult. Maybe we could add a check to the two existing tests that call mergeServiceConfig to verify that the defaults are not modified after mergeServiceConfig returns?
The test copies the entire struct since there can be multiple opaque config maps in it.
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If multiple instances of a service are co-located on the same node then their proxies will all share a cache entry for their resolved service configuration. This is because the cache key contains the name of the watched service but does not take into account the ID of the watching proxies. This means that there will be multiple agent service manager watches that can wake up on the same cache update. These watchers then concurrently modify the value in the cache when merging the resolved config into the local proxy definitions. To avoid this concurrent map write we will only delete the key from opaque config in the local proxy definition after the merge, rather than from the cached value before the merge.
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…orp#10647) If multiple instances of a service are co-located on the same node then their proxies will all share a cache entry for their resolved service configuration. This is because the cache key contains the name of the watched service but does not take into account the ID of the watching proxies. This means that there will be multiple agent service manager watches that can wake up on the same cache update. These watchers then concurrently modify the value in the cache when merging the resolved config into the local proxy definitions. To avoid this concurrent map write we will only delete the key from opaque config in the local proxy definition after the merge, rather than from the cached value before the merge.
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If multiple instances of a service are co-located on the same node then
their proxies will all share a cache entry for their resolved service
configuration. This is because the cache key contains the name of the
watched service but does not take into account the ID of the watching
proxies.
This means that there will be multiple agent service manager watches
that can wake up on the same cache update. These watchers then
concurrently modify the value in the cache when merging the resolved
config into the local proxy definitions.
To avoid this concurrent map write we will only delete the key from
opaque config in the local proxy definition after the merge, rather
than from the cached value before the merge.
Fixes #10636