MongoDB Replica Set Lag and Oplog Window

Shows member state, lag behind the primary and the oplog window. Monitors replication health and resync risk.

#replica-set#lag#oplog

mongodb · javascript

const st = rs.status();
const primary = st.members.find(m => m.stateStr === "PRIMARY");
st.members.map(m => ({
  member: m.name, state: m.stateStr, health: m.health,
  lag_sec: primary ? (primary.optimeDate - m.optimeDate) / 1000 : null,
  ping_ms: m.pingMs
}));
rs.printSecondaryReplicationInfo();   // 4.4 öncesi: rs.printSlaveReplicationInfo()
rs.printReplicationInfo();            // oplog penceresi

Operational Notes & Remediation Guidance

Replica lag exceeding secondary oplog window risks falling off the oplog, requiring full initial sync.

Production Safety & Execution Standards

This script is designed for read-only diagnostics; it does not alter schema or modify data directly.
Prior to executing on production systems under high load, verify the target database version (Min. Version: 4.0).
Exercise caution with mutating actions (e.g., terminating sessions or dropping indexes) referenced in the notes section.

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