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Chapter 8. Troubleshooting resource problems
In case of resource failure, you must investigate the cause and location of the problem, fix the failed resource, and optionally clean up the resource. There are many possible causes of resource failures depending on your deployment, and you must investigate the resource to determine how to fix the problem.
For example, you can check the resource constraints to ensure that the resources are not interrupting each other, and that the resources can connect to each other. You can also examine a Controller node that is fenced more often than other Controller nodes to identify possible communication problems.
8.1. Viewing resource constraints
You can view constraints on how services are launched, including constraints related to where each resource is located, the order in which the resource starts, and whether the resource must be colocated with another resource.
View all resource constraints
On any Controller node, run the pcs constraint show command.
sudo pcs constraint show
$ sudo pcs constraint show
The following example shows a truncated output from the pcs constraint show command on a Controller node:
This output displays the following main constraint types:
- Location Constraints
Lists the locations to which resources can be assigned:
-
The first constraint defines a rule that sets the galera-bundle resource to run on nodes with the
galera-roleattribute set totrue. -
The second location constraint specifies that the IP resource ip-192.168.24.15 runs only on nodes with the
haproxy-roleattribute set totrue. This means that the cluster associates the IP address with thehaproxyservice, which is necessary to make the services reachable. - The third location constraint shows that the ipmilan resource is disabled on each of the Controller nodes.
-
The first constraint defines a rule that sets the galera-bundle resource to run on nodes with the
- Ordering Constraints
Lists the order in which resources can launch. This example shows a constraint that sets the virtual IP address resources IPaddr2 to start before the HAProxy service.
NoteOrdering constraints only apply to IP address resources and to HAproxy. Systemd manages all other resources, because services such as Compute are expected to withstand an interruption of a dependent service, such as Galera.
- Colocation Constraints
- Lists which resources must be located together. All virtual IP addresses are linked to the haproxy-bundle resource.
View Galera location constraints
On any Controller node, run the pcs property show command.
sudo pcs property show
$ sudo pcs property showExample output:
In this output, you can verify that the galera-role attribute is true for all Controller nodes. This means that the galera-bundle resource runs only on these nodes. The same concept applies to the other attributes associated with the other location constraints.
8.2. Investigating Controller node resource problems
Depending on the type and location of the problem, there are different approaches you can take to investigate and fix the resource.
- Investigating Controller node problems
- If health checks to a Controller node are failing, this can indicate a communication problem between Controller nodes. To investigate, log in to the Controller node and check if the services can start correctly.
- Investigating individual resource problems
-
If most services on a Controller are running correctly, you can run the
pcs statuscommand and check the output for information about a specific service failure. You can also log in to the Controller where the resource is failing and investigate the resource behavior on the Controller node.
Procedure
The following procedure shows how to investigate the openstack-cinder-volume resource.
- Locate and log in to the Controller node on which the resource is failing.
Run the
systemctl statuscommand to show the resource status and recent log events:Copy to Clipboard Copied! Toggle word wrap Toggle overflow - Correct the failed resource based on the information from the output.
Run the
pcs resource cleanupcommand to reset the status and the fail count of the resource.sudo pcs resource cleanup openstack-cinder-volume
$ sudo pcs resource cleanup openstack-cinder-volume Resource: openstack-cinder-volume successfully cleaned upCopy to Clipboard Copied! Toggle word wrap Toggle overflow
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