A connection timeout has occurred while attempting to establish a connection to availability replica ‘Node’ with id []. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.

Environment

-> Below message can be seen in the SQL Server errorlog that has Always ON Availability group configured.

A connection timeout has occurred while attempting to establish a connection to availability replica ‘JBSAG3’ with id [322C3054-0352-4F45-A2C2-9328C354051F]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.

-> When a Session timeout occurs between two availability replicas, the availability replicas assume that a failure has occurred and declares a soft error.

-> Failure due to soft error that might cause timeouts are as below,

  • Network errors such as TCP link time-outs, dropped or corrupted packets, or packets that are in an incorrect order.
  • An operating system, server, or database that is not responding.
  • A Windows server timing out.
  • Insufficient computing resources, such as a CPU or disk overload, the transaction log filling up, or the system is running out of memory or threads. In these cases, you must increase the time-out period, reduce the workload, or change the hardware to handle the workload.

-> Above details with regards to soft error is copied from this article.

-> Session timeout value essentially protects SQL Server instance from soft errors by avoiding it to indefinitely wait for a response from other replicas. Always on Availability group uses session time out mechanism by sending out a ping to all connected replicas at a fixed interval. The Replicas ping each other to show that they are still active. If no ping is received from the other replica within the session timeout period, the connection times out and the replica enters the disconnected state.

-> Check the existing Session time out value. Right click Availability group and click properties,

-> The default value for Session timeout is 10 seconds.

-> This message below is logged in SQL Server Error log usually when no ping is received from other replica.

A connection timeout has occurred while attempting to establish a connection to availability replica ‘JBSAG3’ with id [322C3054-0352-4F45-A2C2-9328C354051F]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.

-> To identify the root cause of this issue we can start a continuous ping with a timestamp embedded into it till the issue occurs next time using below powershell command. 

From JBSAG1, ping JBSAG2, JBSAG3. 
From JBSAG2, ping JBSAG1, JBSAG2. 
From JBSAG3, ping JBSAG1, JBSAG2. 

ping.exe -t JBSAG1|Foreach{"{0} - {1}" -f (Get-Date),$_} > C:\temp\ping\JBSAG1.txt
ping.exe -t JBSAG2|Foreach{"{0} - {1}" -f (Get-Date),$_} > C:\temp\ping\JBSAG2.txt
ping.exe -t JBSAG3|Foreach{"{0} - {1}" -f (Get-Date),$_} > C:\temp\ping\JBSAG3.txt

-> When you check the output file after the issue occurred or message is evident in the SQL Server errorlog, you will be able to see a “request timed out” message in the output file.

-> With this details networking team can be contacted to understand the reason why there are ping drops.

-> It could be due to a temporary network issue or some VM level backups happening. Root cause and fix will be required from Networking team.

-> In the meantime, you can increase the session timeout value to a higher value. Increasing the value controls how many seconds that an availability replica waits for a ping response from a connected replica before considering the connection to have failed. By default it is 10 seconds.

-> I increased it to 60 till the network team came out with a solution. In my case it was a temporary ping drop, so 60 seconds value helped me.

-> How to change the session timeout value. Right click availability group and click properties,

-> Once the packet drop was identified (due to VM snapshot in my case) and fixed. I changed the session timeout value back to 10.

Thank You,
Vivek Janakiraman

Disclaimer:
The views expressed on this blog are mine alone and do not reflect the views of my company or anyone else. All postings on this blog are provided “AS IS” with no warranties, and confers no rights.

Always ON – Failed to join database to Availability group

Environment

-> Setting up Always ON,

-> It completed fine. Lets look at the Always ON dashboard,

-> Even though the wizard did not give any errors. The secondaries are not sync and databases are still in restoring mode.

-> Checking the status using below query,

select r.replica_server_name, r.endpoint_url,
rs.connected_state_desc, rs.last_connect_error_description, 
rs.last_connect_error_number, rs.last_connect_error_timestamp 
from sys.dm_hadr_availability_replica_states rs join sys.availability_replicas r
on rs.replica_id=r.replica_id
where rs.is_local=1
GO

Error Message,
Connection attempt failed with error: ‘10060(A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)’.

-> Checking SQL Server errorlog,

Synchronous Secondary – JBSAG2

2020-07-12 16:16:30.730 spid31s Starting up database ‘JBDB’.
2020-07-12 16:16:30.730 spid31s The database ‘JBDB’ is marked RESTORING and is in a state that does not allow recovery to be run.
2020-07-12 16:16:30.750 spid48s The state of the local availability replica in availability group ‘JBSAG’ has changed from ‘RESOLVING_NORMAL’ to ‘NOT_AVAILABLE’. The state changed because either the associated availability group has been deleted, or the local availability replica has been removed from another SQL Server instance. For more information, see the SQL Server error log or cluster log. If this is a Windows Server Failover Clustering (WSFC) availability group, you can also see the WSFC management console.
2020-07-12 16:25:35.710 spid52 The state of the local availability replica in availability group ‘JBSAG’ has changed from ‘NOT_AVAILABLE’ to ‘RESOLVING_NORMAL’. The state changed because the local availability replica is joining the availability group. For more information, see the SQL Server error log or cluster log. If this is a Windows Server Failover Clustering (WSFC) availability group, you can also see the WSFC management console.
2020-07-12 16:25:35.920 spid35s The state of the local availability replica in availability group ‘JBSAG’ has changed from ‘RESOLVING_NORMAL’ to ‘SECONDARY_NORMAL’. The state changed because the availability group state has changed in Windows Server Failover Clustering (WSFC). For more information, see the SQL Server error log or cluster log. If this is a Windows Server Failover Clustering (WSFC) availability group, you can also see the WSFC management console.
2020-07-12 16:25:45.930 spid36s A connection timeout has occurred while attempting to establish a connection to availability replica ‘JBSAG1’ with id [850DE16E-2C2B-43B1-BF52-6D8C5E2046FF]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.
2020-07-12 16:26:12.480 spid52 Starting up database ‘JBDB’.
2020-07-12 16:26:12.490 spid52 The database ‘JBDB’ is marked RESTORING and is in a state that does not allow recovery to be run.

Asynchronous Secondary – JBSAG3

2020-07-12 16:25:47.000 spid57s A connection timeout has occurred while attempting to establish a connection to availability replica ‘JBSAG1’ with id [850DE16E-2C2B-43B1-BF52-6D8C5E2046FF]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.
2020-07-12 16:26:47.060 spid53 Starting up database ‘JBDB’.
2020-07-12 16:26:47.070 spid53 The database ‘JBDB’ is marked RESTORING and is in a state that does not allow recovery to be run.

-> The error message refers to a connection issue between the primary and secondaries.

-> Endpoint uses port 5022. Lets check if port 5022 is not blocked using telnet.

‘telnet’ is not recognized as an internal or external command,
operable program or batch file.

-> Execute below command in powershell to enable telnet.

Install-WindowsFeature -name Telnet-Client

-> Telnet is not working for port 5022. It proves that port 5022 is not open.

-> Let us create a firewall rule to open port 5022.

-> Open “Windows Firewall with Advanced Security” and open “Inbound Rules” on JBSAG1, JBSAG2 and JBSAG3.

-> Once the port 5022 is opened. Lets try joining the secondary database as below,

-> Checking the Status now,

-> Executing below query,

select r.replica_server_name, r.endpoint_url,
rs.connected_state_desc, rs.last_connect_error_description, 
rs.last_connect_error_number, rs.last_connect_error_timestamp 
from sys.dm_hadr_availability_replica_states rs join sys.availability_replicas r
on rs.replica_id=r.replica_id
where rs.is_local=1
GO

-> It works fine now.

Thank You,
Vivek Janakiraman

Disclaimer:
The views expressed on this blog are mine alone and do not reflect the views of my company or anyone else. All postings on this blog are provided “AS IS” with no warranties, and confers no rights.

Always ON – Availability group database is “Not Synchronizing”

Environment

-> Database in Alwayson availability group changed to “Not Synchronizing”.

-> Checking SQL Server errorlog,

Primary – JBSAG1

2020-07-12 14:44:18.530 spid60s A connection timeout has occurred on a previously established connection to availability replica ‘JBSAG2’ with id [24CD3A43-55C6-4352-AA13-0B8B1283BA4D]. Either a networking or a firewall issue exists or the availability replica has transitioned to the resolving role.
2020-07-12 14:44:18.530 spid60s Always On Availability Groups connection with secondary database terminated for primary database ‘JBDB’ on the availability replica ‘JBSAG2’ with Replica ID: {24cd3a43-55c6-4352-aa13-0b8b1283ba4d}. This is an informational message only. No user action is required.
2020-07-12 14:44:18.530 spid67s DbMgrPartnerCommitPolicy::SetSyncAndRecoveryPoint: 24CD3A43-55C6-4352-AA13-0B8B1283BA4D:4
2020-07-12 14:44:18.720 spid67s DbMgrPartnerCommitPolicy::SetSyncAndRecoveryPoint: 24CD3A43-55C6-4352-AA13-0B8B1283BA4D:1
2020-07-12 14:44:18.720 spid67s DbMgrPartnerCommitPolicy::SetSyncAndRecoveryPoint: 24CD3A43-55C6-4352-AA13-0B8B1283BA4D:1
2020-07-12 14:44:18.720 spid67s DbMgrPartnerCommitPolicy::SetSyncState: 24CD3A43-55C6-4352-AA13-0B8B1283BA4D:1
2020-07-12 14:44:19.240 spid43s A connection timeout has occurred on a previously established connection to availability replica ‘JBSAG3’ with id [79FF3186-DF81-45FB-A24B-966BC6EE56EA]. Either a networking or a firewall issue exists or the availability replica has transitioned to the resolving role.
2020-07-12 14:44:19.240 spid43s Always On Availability Groups connection with secondary database terminated for primary database ‘JBDB’ on the availability replica ‘JBSAG3’ with Replica ID: {79ff3186-df81-45fb-a24b-966bc6ee56ea}. This is an informational message only. No user action is required.

Synchronous Secondary – JBSAG2

2020-07-12 14:44:18.530 spid37s Always On Availability Groups connection with primary database terminated for secondary database ‘JBDB’ on the availability replica ‘JBSAG1’ with Replica ID: {208c4c88-7468-4656-97df-4087c5443a74}. This is an informational message only. No user action is required.

Asynchronous Secondary – JBSAG3

2020-07-12 14:44:19.330 spid79s Always On Availability Groups connection with primary database terminated for secondary database ‘JBDB’ on the availability replica ‘JBSAG1’ with Replica ID: {208c4c88-7468-4656-97df-4087c5443a74}. This is an informational message only. No user action is required.
2020-07-12 14:44:29.350 spid28s A connection timeout has occurred while attempting to establish a connection to availability replica ‘JBSAG1’ with id [208C4C88-7468-4656-97DF-4087C5443A74]. Either a networking or firewall issue exists, or the endpoint address provided for the replica is not the database mirroring endpoint of the host server instance.

-> Executing below query,

select r.replica_server_name, r.endpoint_url,
rs.connected_state_desc, rs.last_connect_error_description,
rs.last_connect_error_number, rs.last_connect_error_timestamp
from sys.dm_hadr_availability_replica_states rs join sys.availability_replicas r
on rs.replica_id=r.replica_id
where rs.is_local=1

Primary – JBSAG1

Synchronous Secondary – JBSAG2

Error Message,
Connection attempt failed with error: ‘10060(A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)’.

Asynchronous Secondary – JBSAG3

Error Message,
Connection attempt failed with error: ‘10060(A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)’.

-> The error message refers to a connection issue between the primary and secondaries.

-> Endpoint uses port 5022. Lets check if port 5022 is not blocked using telnet.

‘telnet’ is not recognized as an internal or external command,
operable program or batch file.

-> Execute below command in powershell to enable telnet.

Install-WindowsFeature -name Telnet-Client

-> Telnet is not working for port 5022. It proves that port 5022 is not open.

-> Let us create a firewall rule to open port 5022.

-> Open “Windows Firewall with Advanced Security” and open “Inbound Rules” on JBSAG1, JBSAG2 and JBSAG3.

-> Wait for 5 mins and check the status now by executing below query,

select r.replica_server_name, r.endpoint_url,
rs.connected_state_desc, rs.last_connect_error_description,
rs.last_connect_error_number, rs.last_connect_error_timestamp
from sys.dm_hadr_availability_replica_states rs join sys.availability_replicas r
on rs.replica_id=r.replica_id
where rs.is_local=1

-> After opening port 5022, everything seems to be working fine.

Thank You,
Vivek Janakiraman

Disclaimer:
The views expressed on this blog are mine alone and do not reflect the views of my company or anyone else. All postings on this blog are provided “AS IS” with no warranties, and confers no rights.