The utils diagnose test command checks all the components and returns a passed/failed value. The
components that are essential for the proper functioning of the database replication are:
Network Connectivity:
•
The validate_network command checks all aspects of the network connectivity with all the nodes in the
cluster. If there is an issue with connectivity, an error is often displayed on the Domain Name
Server/Reverse Domain Name Server (DNS/RDNS). The validate_network command completes the
operation in 300 seconds. The common error messages as seen in the network connectivity tests:
- Error "Intra-cluster communication is broken", as shown in this image.
Cause
•
This error is caused when one or more nodes in the cluster have a network connectivity problem. Ensure that
all the nodes have ping reachability.
Effect
•
If the intra-cluster communication is broken, database replication issues occur.
- Reverse DNS lookup failed.
Cause
•
This error is caused when the reverse DNS lookup fails on a node. However, you can verify whether the
DNS is configured and functions properly when you use these commands:
utils network eth0 all - Shows the DNS configuration (if present)
utils network host <ip address/Hostname> - Checks for resolution of ip address/Hostname
Effect
•
If the DNS does not function correctly, it can cause database replication issues when the servers are defined
and use the hostnames.
Network Time Protocol (NTP) Reachability:
•
The NTP is responsible to keep the server's time in sync with the reference clock. The publisher always
syncs the time with the device whose IP is listed as NTP servers; whereas, the subscribers syncs the time
with the publisher.
It is extremely important for the NTP to be fully functional in order to avoid any database replication issues.
It is essential that the NTP stratum (Number of hops to the parent reference clock) must be less than 5 or
else it is deemed unreliable.
Complete these steps in order to check NTP status:
Use the utils diagnose test command to check the output, as shown in this image.