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HADR_ARCONTROLLER_NOTIFICATIONS_SUBSCRIBER_LIST

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Description:

This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of reading or updating the list of availability group event subscribers.

(Books Online description: “The publisher for an availability replica event (such as a state change or configuration change) is waiting for exclusive read/write access to the list of event subscribers.  Internal use only.”)

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Added in SQL Server version:

2012

Removed in SQL Server version:

N/A

Extended Events wait_type value:

Maps to the HADR_ARPROXY_NOTIFICATION_SUBSCRIBER_LIST map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here).

The map_key value in sys.dm_xe_map_values is 837 in 2012 and 856 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

I have not seen this wait type be a noticeable contention point.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for access to the event subscriber list (in this case, while doing routine sending of log blocks from the principal replica to secondary replicas)
  2. Waiting for access to the event subscriber list (in this case, while making some kind of change to the availability group, I think)

And other similar call stacks.

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+1f9
    SOS_RecursiveMutex::Wait+78
    CHadrPublisher::GetSubscriberInfoWithRef+5d
    CHadrPublisher::GetTransportWithRef+26
    CHadrArManager::GetTransportWithRef+9d
    HadrReplicaManagerWrapper::GetTransportWithRef+b8
    DbMgrPartner::SendNextMessage+55
    DbMgrPartner::BuildAndSendLogMsg+7b
    DbMgrPartner::StartScans+24b
    HadrWorkItem::Execute+151
    HadrWorkRoutine+1c5
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8
  2. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+1f9
    SOS_RecursiveMutex::Wait+78
    CHadrPublisher::GetSubscriberInfoWithRef+5d
    CHadrPublisher::GetTransportWithRef+26
    CHadrArManager::GetTransportWithRef+9d
    HadrReplicaManagerWrapper::GetTransportWithRef+b8
    CHadrRecvMsgData::Dispatch+961
    CSbTransportRecvMsg::Dispatch+6e
    CSbEndpointState::TriggerEvent+407
    CSbEndpointState::DispatchMessageW+3ac
    CConnectionEndpoint::DelimitOneRecvMessage+1e1
    CConnectionEndpoint::ReceiveTask_IdempotentInvoke+6dd
    CConnectionReceiveTask::IdempotentInvoke+15
    CSbTaskManager::HandleReusableTask+264
    CSbTask::TaskStart+14b
    CSbTask::BeginTaskStart+17
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8