Scatter-Gather Queries in a Sharded MongoDB Cluster

Measures queries fanning out to all shards via mongos. Used to evaluate shard key choice and query targeting.

#sharding#scatter-gather#mongos

mongodb · javascript

db.serverStatus().metrics.queryExecutor;

// mongos üzerinde hedefleme oranı: scannedObjects / returned ne kadar yüksekse,
// sorgu o kadar çok shard'a dağılıyor demektir.
db.getSiblingDB("admin").runCommand({ serverStatus: 1 }).metrics.query;

Operational Notes & Remediation Guidance

Queries without shard key predicates target all shards (scatter-gather), causing network overhead and latency spikes.

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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