Prisma Migration Engine

This directory contains the crates that belong to the migration engine behind prisma-migrate.

The code and documentation for the executable binary are in the cli directory.

The core logic shared across connectors is in the core directory.

The connector interface and the built-in connectors are in the connectors directory.

API

The TypeScript CLI in prisma/prisma interacts with the binary compiled from the cli crate. Some commands are exposed through the CLI directly, like create-database, but most of them through the JSON-RPC API, which is the default command if you just run the migration-engine binary. These two sets of commands are separated because previously, you needed a valid database connection to the database referenced in the Prisma schema to start a migration engine instance, but we did not have that requirement in commands like migration-engine cli create-database. This is legacy, as the JSON-RPC API now connects lazily.

The reason why we have a JSON-RPC API in the first place is so the TypeScript CLI can issue multiple commands on the same connection, get results back and act on them.

Logging and crash reporting happens through JSON logs on the Migration Engine's stderr. Every line contains a single JSON object conforming to the following interface:

interface StdErrLine {
  timestamp: string;
  level: LogLevel;
  fields: LogFields;
}

interface LogFields {
  message: string;

  /// Only for ERROR level messages
  is_panic?: boolean;
  error_code?: string;

  [key: string]: any;
}

type LogLevel = "INFO" | "ERROR" | "DEBUG" | "WARN";

Exit codes

0: normal exit
1: abnormal (error) exit
101: panic

Non-zero exit codes should always be accompanied by a log message on stderr with the ERROR level.