internal/client: remove the lock for idle connection recycle #278
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Signed-off-by: tiancaiamao <tiancaiamao@gmail.com>
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Update: |
Signed-off-by: tiancaiamao <tiancaiamao@gmail.com>
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Signed-off-by: tiancaiamao <tiancaiamao@gmail.com>
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| // An idle connArray will not change to active again, this avoid the race condition | ||
| // that recycling idle connection close an active connection unexpectedly (idle -> active). | ||
| if array.batchConn != nil && array.isIdle() { |
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I confirmed return error will not make TiDB unavailable.
This error will be recognized as a RPC error, and TiDB will refresh the region cache ... and retry the request.
There was a problem hiding this comment.
I confirmed return error will not make TiDB unavailable.
This error will be recognized as a RPC error, and TiDB will refresh the region cache ... and retry the request.
This behavior is a magic, it's hard to figure out that tidb will retry the request while reading the source code. Could you add some notes here and file an issue? Also, we should do refactor to make sure we know when should return a "retry" error.
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do we need cherry-pick this to 5.0, 4.0? |
I'm not sure, the case is not so common. @lysu |
Signed-off-by: tiancaiamao <tiancaiamao@gmail.com>
Signed-off-by: tiancaiamao <tiancaiamao@gmail.com>
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TiDB issue traced in pingcap/tidb#32500 |
After mock testing, I find #270 is not sufficient to solve the problem.
To my surprise, RLock can block RLock in some case
The final decision is to reduce the granularity of the lock.
Just lock the modification of the
map...There is a risk that an idle connection become active again.
Since
recycleMuis removed to protect such case, in very rare cases, someone maybe using the connection and the connection is closed by the recycle operation.I think the outcome is acceptable, comparing to the recycle operation blocks the
SendRequest()function.Signed-off-by: tiancaiamao tiancaiamao@gmail.com