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DISCLAIMER: APPC has been moved to maria db since Casablanca Release. This page is just for your reference. It's not going to apply for APPC after Casablanca. (Takamune Cho 2/21/2019)
Note, this page is based on the SDNC DB (MySQL) Clustered Deployment Wiki page as created by Rahul Sharma.
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- StatefulSet:
- Used to manage Stateful applications.
- Guarantees fixed numbering for a POD.
- Using headless service, PODs were registered with their own unique FQDN in DNS; this makes it possible for other PODs to find a POD even after a restart (albeit with a different IPAddress).
- Since we were using a single Kubernetes VM, hosting a volume dynamically on the local-store VM for newly spun slaves was not straight-forward (support wasn't inbuilt). However, Kubernetes does support writing external provisioners which did the job for us. This provisioner actually created a virtual NFS Server on top of a local store. The instance of nfs-provisioner will watch for
PersistentVolumeClaimsthat ask for theStorageClassand automatically create NFS-backedPersistentVolumesfor them.
We used this Kubernetes example to replicate MySQL server; this was modified to suit the needs for APPC DB.
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Unfortunately, if a master fails, then we need to write a script (or an application) to promote one of the slaves to be the master and instruct the other slaves and applications to change to the new master. You can see more details here.
The other option is to use GTID-based replication.
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