mongodb-replication-sharding

name	mongodb-replication-sharding
version	2.1.0
description	Master MongoDB replication, replica sets, and sharding for distributed deployments. Learn failover, shard keys, and cluster management. Use when setting up high availability or scaling horizontally.
sasmp_version	1.3.0
bonded_agent	05-mongodb-replication-sharding
bond_type	PRIMARY_BOND
capabilities	["replica-set-setup","sharding-configuration","failover-management","shard-key-design","cluster-monitoring"]
input_validation	{"required_context":["deployment_type","availability_requirements"],"optional_context":["data_size","geographic_distribution","rpo_rto_targets"]}
output_format	{"topology_design":"object","configuration_steps":"array","monitoring_setup":"object","failover_procedure":"object"}
error_handling	{"common_errors":[{"code":"REP001","condition":"No primary in replica set","recovery":"Check member connectivity, verify election priority, review heartbeat"},{"code":"REP002","condition":"Replication lag too high","recovery":"Check oplog size, network latency, secondary hardware"},{"code":"REP003","condition":"Shard key causing hotspot","recovery":"Analyze chunk distribution, consider resharding with hashed key"}]}
prerequisites	{"mongodb_version":"4.0+","required_knowledge":["basic-administration","networking-basics"],"infrastructure_requirements":["Minimum 3 nodes for replica set","Minimum 3 config servers for sharding"]}
testing	{"unit_test_template":"// Verify replica set status\nconst status = await admin.command({ replSetGetStatus: 1 })\nexpect(status.members.filter(m => m.stateStr === 'PRIMARY')).toHaveLength(1)\nexpect(status.members.filter(m => m.stateStr === 'SECONDARY').length).toBeGreaterThanOrEqual(1)\n"}

MongoDB Replication & Sharding

Master distributed MongoDB architectures.

Quick Start

Replica Set Setup

# Start mongod instances with replica set config
mongod --replSet rs0 --port 27017
mongod --replSet rs0 --port 27018
mongod --replSet rs0 --port 27019

# Initiate replica set
mongo mongodb://localhost:27017
> rs.initiate({
    _id: 'rs0',
    members: [
      { _id: 0, host: 'localhost:27017', priority: 1 },
      { _id: 1, host: 'localhost:27018', priority: 0.5 },
      { _id: 2, host: 'localhost:27019', priority: 0 }
    ]
  })

# Check replica set status
> rs.status()

Replication Concepts

Primary: Accepts reads and writes
Secondary: Replicates from primary, serves reads only
Arbiter: Participates in elections, no data

Write Concerns

// Unacknowledged
await collection.insertOne(doc, { writeConcern: { w: 0 } })

// Acknowledged (single node)
await collection.insertOne(doc, { writeConcern: { w: 1 } })

// Majority
await collection.insertOne(doc, { writeConcern: { w: 'majority' } })

// Majority with timeout
await collection.insertOne(doc, {
  writeConcern: { w: 'majority', wtimeout: 5000 }
})

Read Preferences

// Read from primary only (default)
find().()


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