Some tips to upgrade SAFR Cluster

When you upgrade (version up) SAFR cluster, you shoud plan the procedure carefully.

1. You must upgrade SAFR Primary first. After that, you can upgrade SAFR Secondary servers one by one.
2. If the new version needs mongo db schema change, or face signature update, you will need to have maintenance window. Please consult to the release note and SAFR support.
3. After upgrading SAFR Primary, before upgrading SAFR Secondaries, you must verify the mongoDB config is synced between the member nodes. Verify the replica set config on all nodes using rs.conf() command. Pay special attention to the ""version"" field. If you find discrepancies in the configuration, try to manually re-sync the configuration using the rs.reconfig() command. Be careful, though, as this operation can cause downtime.
4. If a secondary doesn't sync to existing mongo cluster by config version discrepancies, you may need to run mongo db  ""initial sync"" procedure.