Network Management

Cannot create the HA pool. A pool must have both active and standby members

This article explains an issue with the HA pool setup wizard, which throws an error message: "Cannot create an HA pool. A pool must have both active and standby members". This symptom is due to bad or incomplete previous HA failover and must be manually cleaned up.

First published date

10/21/2018 11:52 PM

Last published date

2/18/2025 4:38 PM

Overview

When setting up a High Availability (HA) pool via web console, you can see the following error message:

Cannot create the HA pool. A pool must have both active and standby members.

update-screenshot.jpg

And upon checking the HA_PoolMembers table we see two Old Pool Member showing up as Main Poller still exists, but the same members to not exists in OrionServers Table.

Similar error pops up while Creating/Editing a HA Pool
image.png

Product section

Orion Platform

Cause

1. Case sensitive Hostnames for Pool Members
Hostname matching in earlier versions of HA is case-sensitive. If the Machine's Host Name is in lower case and HA picks up the machine name in upper case, then Orion Platform cannot match pool members to Orion Servers and engines. 

You can verify this in the Engines and HA_PoolMembers tables:

  1. Run the Database Manager and navigate to the Engines table. See Use Database Manager to view the SolarWinds database .
  2. Right-click the table, select Query table, and Execute the default query. Note the case for hostnames.engine table-2.jpg
  3. Right-click the HA_PoolMembers table, select Query table, and Execute the default query. Engine table 3.jpg
  4. Compare HostNames in both tables:
    • HA_PoolMembers stores the information in upper case
    • OrionServers and engines have the name in lower case
2. Both the Pool Members were showing as Active per HA_PoolMembers table because there are two entries i.e two active members in HA_ResourcesInstancesTable instead of just one(active member only).

3.  Registry and DB entry values for PoolMemberType do not match

 

Resolution

It is important to state that if the problem continues to occur, please gather diagnostics and file a support case with SolarWinds support to help root cause and prevent the problem from occurring in the future.

 

Scenario1: Due to Case Sensitive Hostnames of Pool Members
For customers using HA v2 and higher

  1. Ensure HA_PoolMembers table does not have reference to Old Orion Servers if you have recently migrated the Orion Servers with new Hostnames.
  2. If there are any reference to Orion hostname - verify the same in OrionServers table and make sure the data here matches the data in HA_PoolMembers after deleting the old Servers names.

NPM 12.1(deprecated) and below customers
To resolve this issue, upgrade NPM to version 12.2 or later, or follow the following steps:

  1. In Windows, change the Machine Name to correspond with the name in the HA_PoolMembers table. In this example, change the Machine Name to upper case. For more details, consult the documentation for your Windows version.
  2. Update Engines and Orion Servers.

You should be able to create the HA pool now.

If the same issue occurs consider a full rebuild of the SolarWinds High Availability by performing the easy to follow steps in the article, How to rebuild SolarWinds High Availability.

Learn more:


Scenario 2: Multiple Active Members entries from same pool in HA Tables exists
Before performing these steps, HA must be disabled and services on both pool members must be stopped.

1. Find out if the two pool members showing as active in registry and in HA_PoolMembers Table
2. Check if there is an extra entry for the two members in HA_ResourcesInstances table for example:
image.png
3. Remove the extra entry from HA_ResourcesInstances Table after stopping All services on both member servers. 
4. Fix the Registry on Standby Member server to have Standby for both Runtype and Installtype
5. Fix the HA_PoolMembers table for the two member. Active member should have AdditionalPoller and Standby Should have AdditonalPollerStandby entries in PoolMemberType Column.
6. Start the Services on both Member servers.
7. Verify Registry and DB entries still holding correctly in PoolMemberType Column
8. Go to My Deployment page and try creating the HA pool for these members server. The error message should not appear anymore.

Scenario 3: Registry and DB entry values for PoolMemberType do not match on one or more server in the pool
Follow the steps in How to rebuild SolarWinds High Availability