MongoDB¶

Overview¶

MongoDB is a document database used for storing application data with flexible schemas.

Deployment¶

Kubernetes Resources¶

Resource	Name	Namespace
Deployment	mongodb	databases
Service	mongodb	databases
PVC	mongodb-data	databases

Configuration¶

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mongodb
  namespace: databases
spec:
  replicas: 1
  template:
    spec:
      containers:
      - name: mongodb
        image: mongo:7
        ports:
        - containerPort: 27017
        volumeMounts:
        - name: data
          mountPath: /data/db

Access¶

Connection Details¶

Property	Value
Host	mongodb.databases.svc
Port	27017
Protocol	MongoDB Wire

Connection String¶

mongodb://username:[email protected]:27017/dbname?authSource=admin

Databases¶

Configured Databases¶

Database	Purpose
hub	Hub application data
admin	Administrative
local	Local operations

Collections¶

Hub Database¶

Collection	Description
users	User profiles
sessions	Active sessions
configurations	App settings

Queries¶

Basic Operations¶

// Find documents
db.collection.find({ field: "value" })

// Insert document
db.collection.insertOne({ field: "value" })

// Update document
db.collection.updateOne(
  { _id: ObjectId("...") },
  { $set: { field: "new value" } }
)

// Delete document
db.collection.deleteOne({ _id: ObjectId("...") })

Aggregation Pipeline¶

db.collection.aggregate([
  { $match: { status: "active" } },
  { $group: { _id: "$category", count: { $sum: 1 } } },
  { $sort: { count: -1 } }
])

Indexes¶

Creating Indexes¶

// Single field index
db.collection.createIndex({ field: 1 })

// Compound index
db.collection.createIndex({ field1: 1, field2: -1 })

// Text index for search
db.collection.createIndex({ content: "text" })

Index Recommendations¶

Collection	Fields	Type
users	email	Unique
sessions	userId, createdAt	Compound
logs	timestamp	TTL

Authentication¶

Users¶

User	Database	Roles
admin	admin	root
hubUser	hub	readWrite

Creating User¶

db.createUser({
  user: "appUser",
  pwd: "password",
  roles: [
    { role: "readWrite", db: "mydb" }
  ]
})

Backup¶

mongodump¶

mongodump \
  --uri="mongodb://user:pass@mongodb:27017" \
  --out=/backup/mongodb \
  --gzip

mongorestore¶

mongorestore \
  --uri="mongodb://user:pass@mongodb:27017" \
  --gzip \
  /backup/mongodb

Monitoring¶

Key Metrics¶

Metric	Description
connections.current	Active connections
opcounters.query	Queries/sec
opcounters.insert	Inserts/sec
mem.resident	Memory usage

Health Check¶

db.runCommand({ serverStatus: 1 })
db.runCommand({ dbStats: 1 })

Performance¶

Query Optimization¶

Use indexes for frequent queries
Limit returned fields with projection
Use explain() to analyze queries
Avoid large document arrays

Explain Plan¶

db.collection.find({ field: "value" }).explain("executionStats")

Troubleshooting¶

Common Issues¶

Issue	Cause	Resolution
Slow queries	Missing index	Add appropriate index
Connection refused	Auth failure	Check credentials
Out of memory	Large documents	Increase resources
Lock timeout	Write contention	Optimize writes

Logs¶

kubectl logs -n databases deployment/mongodb