mirror of
https://github.com/matrix-org/dendrite
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f8d3a762c4
* Add a per-room mutex to federationapi when processing transactions This has numerous benefits: - Prevents us doing lots of state resolutions in busy rooms. Previously, room forks would always result in a state resolution being performed immediately, without checking if we were already doing this in a different transaction. Now they will queue up, resulting in fewer calls to `/state_ids`, `/g_m_e`, etc. - Prevents memory usage from growing too large as a result and potentially OOMing. And costs: - High traffic rooms will be slightly slower due to head-of-line blocking from other servers, though this has always been an issue as roomserver has a per-room mutex already. * Fix unit tests * Correct mutex lock ordering
38 lines
706 B
Go
38 lines
706 B
Go
package internal
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import "sync"
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type MutexByRoom struct {
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mu *sync.Mutex // protects the map
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roomToMu map[string]*sync.Mutex
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}
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func NewMutexByRoom() *MutexByRoom {
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return &MutexByRoom{
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mu: &sync.Mutex{},
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roomToMu: make(map[string]*sync.Mutex),
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}
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}
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func (m *MutexByRoom) Lock(roomID string) {
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m.mu.Lock()
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roomMu := m.roomToMu[roomID]
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if roomMu == nil {
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roomMu = &sync.Mutex{}
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}
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m.roomToMu[roomID] = roomMu
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m.mu.Unlock()
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// don't lock inside m.mu else we can deadlock
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roomMu.Lock()
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}
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func (m *MutexByRoom) Unlock(roomID string) {
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m.mu.Lock()
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roomMu := m.roomToMu[roomID]
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if roomMu == nil {
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panic("MutexByRoom: Unlock before Lock")
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}
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m.mu.Unlock()
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roomMu.Unlock()
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}
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