MongoDB Log Storage

Kashvi can mirror all application logs to MongoDB in addition to stdout. The integration is:

Async — writes never block the request path
Batched — up to 50 documents per InsertMany
Graceful — remaining records are flushed before the server exits
Optional — leave MONGO_URI blank to stay stdout-only (zero overhead)

Configuration

.envgo

MONGO_URI=mongodb://localhost:27017   # required to enable; leave blank to disable
MONGO_LOG_DB=kashvi_logs              # default: kashvi_logs
MONGO_LOG_COLLECTION=app_logs         # default: app_logs

With a MongoDB Atlas cluster:

.envgo

MONGO_URI=mongodb+srv://user:pass@cluster.mongodb.net/?retryWrites=true

Document shape

Each log record in MongoDB:

gogo

{
  "time":       "2026-02-25T12:00:00Z",
  "level":      "INFO",
  "msg":        "user registered",
  "request_id": "a1b2c3d4",
  "attrs": {
    "email": "user@example.com",
    "plan":  "pro"
  }
}

A {time: -1} index is created on startup for efficient querying.

Querying logs

gogo

// mongosh — last 100 errors
db.app_logs.find({ level: "ERROR" }).sort({ time: -1 }).limit(100)

// All logs from a specific request
db.app_logs.find({ request_id: "a1b2c3d4" })

// Logs from the last hour
db.app_logs.find({ time: { $gt: new Date(Date.now() - 3600_000) } })

TTL (auto-delete old logs)

Add a TTL index in MongoDB to keep only N days of logs:

gogo

db.app_logs.createIndex(
  { time: 1 },
  { expireAfterSeconds: 30 * 24 * 3600 }  // 30 days
)

Graceful flush on shutdown

logger.CloseMongoHandler() is called automatically during kashvi run shutdown. If you start the server manually, call it yourself:

gogo

defer logger.CloseMongoHandler()

Internal design

Detail	Value
Channel buffer	4096 records
Batch size	50 documents per InsertMany
Flush ticker	Every 2 seconds
On queue full	Record silently dropped — logging never blocks
Connection pool	Max 10 MongoDB connections
Connect timeout	5 seconds (falls back to stdout if unreachable)

Unreachable MongoDB

If MongoDB is unreachable at startup, Kashvi logs a warning to stdout and continues without MongoDB — it never fails to start.