Configuration flags

FerretDB provides numerous configuration flags you can customize to suit your needs and environment. You can always see the complete list by using --help flag. To make user experience cloud native, every flag has its environment variable equivalent. There is no configuration file.

info

Some default values are overridden in our Docker image.

General

Flag	Description	Environment Variable	Default Value
-h, --help	Show context-sensitive help		false
--version	Print version to stdout and exit		false
--handler	Backend handler	FERRETDB_HANDLER	pg (PostgreSQL)
--mode	Operation mode	FERRETDB_MODE	normal
--state-dir	Path to the FerretDB state directory (set to - to disable)	FERRETDB_STATE_DIR	. (/state for Docker)
--repl-set-name	Replica set name (should be set for OpLog to work correctly)	FERRETDB_REPL_SET_NAME	empty

Interfaces

Flag	Description	Environment Variable	Default Value
--listen-addr	Listen TCP address	FERRETDB_LISTEN_ADDR	127.0.0.1:27017 (:27017 for Docker)
--listen-unix	Listen Unix domain socket path	FERRETDB_LISTEN_UNIX
--listen-tls	Listen TLS address (see here)	FERRETDB_LISTEN_TLS
--listen-tls-cert-file	TLS cert file path	FERRETDB_LISTEN_TLS_CERT_FILE
--listen-tls-key-file	TLS key file path	FERRETDB_LISTEN_TLS_KEY_FILE
--listen-tls-ca-file	TLS CA file path	FERRETDB_LISTEN_TLS_CA_FILE
--proxy-addr	Proxy address	FERRETDB_PROXY_ADDR
--proxy-tls-cert-file	Proxy TLS cert file path	FERRETDB_PROXY_TLS_CERT_FILE
--proxy-tls-key-file	Proxy TLS key file path	FERRETDB_PROXY_TLS_KEY_FILE
--proxy-tls-ca-file	Proxy TLS CA file path	FERRETDB_PROXY_TLS_CA_FILE
--debug-addr	Listen address for HTTP handlers for metrics, profiling, etc (set to - to disable)	FERRETDB_DEBUG_ADDR	127.0.0.1:8088 (:8088 for Docker)

Backend handlers

PostgreSQL

PostgreSQL backend can be enabled by --handler=pg flag or FERRETDB_HANDLER=pg environment variable.

Flag	Description	Environment Variable	Default Value
--postgresql-url	PostgreSQL URL for 'pg' handler	FERRETDB_POSTGRESQL_URL	postgres://127.0.0.1:5432/ferretdb

FerretDB uses pgx v5 library for connecting to PostgreSQL. Supported URL parameters are documented there:

• https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#ParseConfig
• https://pkg.go.dev/github.com/jackc/pgx/v5#ParseConfig
• https://pkg.go.dev/github.com/jackc/pgx/v5/pgxpool#ParseConfig

Additionally:

• pool_max_conns parameter is set to 50 if it is unset in the URL;
• application_name is always set to "FerretDB";
• timezone is always set to "UTC".

SQLite

SQLite backend can be enabled by --handler=sqlite flag or FERRETDB_HANDLER=sqlite environment variable.

Flag	Description	Environment Variable	Default Value
--sqlite-url	SQLite URI (directory) for 'sqlite' handler	FERRETDB_SQLITE_URL	file:data/ . (file:/state/ for Docker)

FerretDB uses modernc.org/sqlite library for accessing SQLite database files. Supported URL parameters are documented there:

• https://www.sqlite.org/uri.html
• https://pkg.go.dev/modernc.org/sqlite#Driver.Open
• https://www.sqlite.org/pragma.html

Additionally:

• _pragma=auto_vacuum(none) parameter is set if that PRAGMA is not present;
• _pragma=busy_timeout(10000) parameter is set if that PRAGMA is not present;
• _pragma=journal_mode(wal) parameter is set if that PRAGMA is not present.

One difference is that URI should point to the existing directory (with absolute or relative path), not to a single database file. That allows FerretDB to work with multiple databases.

In-memory SQLite databases are fully supported. In that case, the URI should still point to the existing directory (that will be unused). For example: file:./?mode=memory.

Miscellaneous

Flag	Description	Environment Variable	Default Value
--log-level	Log level: 'debug', 'info', 'warn', 'error'	FERRETDB_LOG_LEVEL	info
--[no-]log-uuid	Add instance UUID to all log messages	FERRETDB_LOG_UUID
--[no-]metrics-uuid	Add instance UUID to all metrics	FERRETDB_METRICS_UUID
--otel-traces-url	OpenTelemetry OTLP/HTTP traces endpoint URL (e.g. http://host:4318/v1/traces)	FERRETDB_OTEL_TRACES_URL	empty (disabled)
--telemetry	Enable or disable basic telemetry	FERRETDB_TELEMETRY	undecided