Configuring logging

Use the PrismaClient log parameter to configure log levels , including warnings, errors, and information about the queries sent to the database.

Prisma supports two types of logging:

• Logging to stdout (default)
• Event-based logging (use $on() method to subscribe to events)

Log to stdout

The simplest way to print all log levels to stdout is to pass in an array LogLevel objects:

const prisma = new PrismaClient({
  log: ['query', 'info', 'warn', 'error'],
})

This is the short form of passing in an array of LogDefinition objects where the value of emit is always stdout:

const prisma = new PrismaClient({
  log: [
    {
      emit: 'stdout',
      level: 'query',
    },
    {
      emit: 'stdout',
      level: 'error',
    },
    {
      emit: 'stdout',
      level: 'info',
    },
    {
      emit: 'stdout',
      level: 'warn',
    },
  ],
})

Event-based logging

To use event-based logging:

1. Set emit to event for a specific log level, such as query
2. Use the $on() method to subscribe to the event

The following example subscribes to all query events and write the duration and query to console:

const prisma = new PrismaClient({
  log: [
    {
      emit: 'event',
      level: 'query',
    },
    {
      emit: 'stdout',
      level: 'error',
    },
    {
      emit: 'stdout',
      level: 'info',
    },
    {
      emit: 'stdout',
      level: 'warn',
    },
  ],
})

prisma.$on('query', (e) => {
  console.log('Query: ' + e.query)
  console.log('Duration: ' + e.duration + 'ms')
})

Query: SELECT "public"."User"."id", "public"."User"."email", "public"."User"."name" FROM "public"."User" WHERE 1=1 OFFSET $1
Duration: 3ms
Query: SELECT "public"."Post"."id", "public"."Post"."title", "public"."Post"."authorId" FROM "public"."Post" WHERE "public"."Post"."authorId" IN ($1,$2,$3,$4) OFFSET $5
Duration: 2ms

The exact event (e) type and the properties available depends on the log level.