Introducing Replication cli Commands

status

rs.status();

• gives deets on each node in replication set
• data it gets is from the heartbeats between nodes
• gives THE MOST info on each node in the set: this contains the members array

status member stat highlights

• state: can show primary
• uptime: how long its been running for
• optime: last time it applied an operation from its opLog
• heartbeatIntervalMillis: default to 2s, how frequently the nodes talk to each other

WHICH node this rs.status() is run from impacts the output. Heartbeat stats will return for other nodes than the one that the status command was run from

isMaster

rs.isMaster();

• gives deets on the single node that it was run on
• output is shorter than status

isMaster stat highlights

• primary: the name of the primary node in the set, regardless of which node this was run on
• secondary
• isMaster

NOTE
rs.isMaster is a wrapper around db.isMaster()

serverStatus

• has LOTS of stuff
• can be scoped to a specific part of the output, which is the focus from here on

limiting serverStatus output

db.serverStatus()['repl'];

• similar to rs.isMaster
• rbid is NOT included in isMaster: counts how many rollbacks have been performed on the node

printReplicationInfo

• only has oplog data
• only returns current node's data
• contains timestamps for first + last events in the oplog
• contains MB size of the oplog
• does NOT contain the olpog statements: only this "metadata" of times and oplog size