MongoDB vs Couchbase

Audits WiredTiger cache dirty bytes, checkpoint durations, oplog retention windows, and active write tickets.

# 1. Inspect WiredTiger cache utilization, dirty page thresholds, and checkpoint times
mongosh --eval '
const wt = db.serverStatus().wiredTiger.cache;
print("WT Cache Used (MB):    " + (wt["bytes currently in the cache"] / 1024 / 1024).toFixed(2));
print("WT Dirty Bytes (MB):   " + (wt["tracked dirty bytes in the cache"] / 1024 / 1024).toFixed(2));
print("WT Max Cache Size (MB):" + (wt["maximum bytes configured"] / 1024 / 1024).toFixed(2));
print("Checkpoint Duration:   " + wt["last checkpoint elapsed time (ms)"] + " ms");
'

# 2. Check replica set oplog window and secondary replication lag
mongosh --eval 'rs.printReplicationInfo(); rs.printSecondaryReplicationInfo();'

# 3. Identify unindexed operations holding concurrent write tickets
mongosh --eval 'db.currentOp({"secs_running": {"$gt": 3}, "waitingForLock": true})'

Audits ep-engine memory usage, OOM drops, active vBucket partition count, and XDCR replication stream lag.

# 1. Audit ep-engine memory usage, OOM drops, and active vBucket partition count
cbstats localhost:11210 all | 
grep -E "(ep_oom_errors|ep_tmp_oom_errors|mem_used|ep_max_size|vb_active_num|curr_items)"

# 2. Inspect online cluster rebalance progress and active data migrations
curl -s -u Admin:$CB_PASSWORD http://localhost:8091/pools/default/rebalanceProgress | jq .

# 3. Monitor XDCR replication pipeline latency and queue backlog size
curl -s -u Admin:$CB_PASSWORD http://localhost:8091/pools/default/tasks | 
jq '.[] | select(.type=="xdcr") | {source: .source, target: .target, changesLeft: .changesLeft, status: .status}'