Sync service configuration

This page documents the config options for self-hosting the Electric sync engine.

Advanced only

You don't need to worry about this if you're using Electric Cloud.

Also, the only required configuration is DATABASE_URL.

Configuration

The sync engine is an Elixir application developed at packages/sync-service and published as a Docker image at electricsql/electric.

Configuration options can be provided as environment variables, e.g.:

docker run \
    -e "DATABASE_URL=postgresql://..." \
    -e "ELECTRIC_DB_POOL_SIZE=10" \
    -p 3000:3000 \
    electricsql/electric

These are passed into the application via config/runtime.exs.

Database

DATABASE_URL

Variable	DATABASE_URLrequired
Description	Postgres connection string. Used to connect to the Postgres database. The connection string must be in the libpg Connection URI format of postgresql://[userspec@][hostspec][/dbname][?sslmode=<sslmode>]. The userspec section of the connection string specifies the database user that Electric connects to Postgres as. They must have the REPLICATION role. For a secure connection, set the sslmode query parameter to require.
Example	DATABASE_URL=postgresql://user:password@example.com:54321/electric

ELECTRIC_DATABASE_USE_IPV6

Variable	ELECTRIC_DATABASE_USE_IPV6
Default	false
Description	Set to true to prioritise connecting to the database over IPv6. Electric will fall back to an IPv4 DNS lookup if the IPv6 lookup fails.
Example	ELECTRIC_DATABASE_USE_IPV6=true

ELECTRIC_DB_POOL_SIZE

Variable	ELECTRIC_DB_POOL_SIZE
Default	20
Description	How many connections Electric opens as a pool for handling shape queries.
Example	ELECTRIC_DB_POOL_SIZE=10

ELECTRIC_REPLICATION_STREAM_ID

Variable	ELECTRIC_REPLICATION_STREAM_ID
Default	default
Description	Suffix for the logical replication publication and slot name.
Example	ELECTRIC_REPLICATION_STREAM_ID=my-app

Electric

ELECTRIC_INSTANCE_ID

Variable	ELECTRIC_INSTANCE_ID
Default	Electric.Utils.uuid4()
Description	A unique identifier for the Electric instance. Defaults to a randomly generated UUID.
Example	ELECTRIC_INSTANCE_ID=some-unique-instance-identifier

ELECTRIC_SERVICE_NAME

Variable	ELECTRIC_SERVICE_NAME
Default	electric
Description	Name of the electric service. Used as a resource identifier and namespace.
Example	ELECTRIC_SERVICE_NAME=my-electric-service

ELECTRIC_ENABLE_INTEGRATION_TESTING

Variable	ELECTRIC_ENABLE_INTEGRATION_TESTING
Default	false
Description	Expose some unsafe operations that faciliate integration testing. Do not enable this production.
Example	ELECTRIC_ENABLE_INTEGRATION_TESTING=true

ELECTRIC_LISTEN_ON_IPV6

Variable	ELECTRIC_LISTEN_ON_IPV6
Default	false
Description	By default, Electric binds to IPv4. Enable this to listen on IPv6 addresses as well.
Example	ELECTRIC_LISTEN_ON_IPV6=true

ELECTRIC_LOG_CHUNK_BYTES_THRESHOLD

Variable	ELECTRIC_LOG_CHUNK_BYTES_THRESHOLD
Default	10485760
Description	Limit the maximum size of a shape log response, to ensure they are cached by upstream caches. Defaults to 10MB (10 * 1024 * 1024). See #1581 for context.
Example	ELECTRIC_LOG_CHUNK_BYTES_THRESHOLD=20971520

ELECTRIC_LOG_OTP_REPORTS

Variable	ELECTRIC_LOG_OTP_REPORTS
Default	false
Description	Enable OTP SASL reporting at runtime.
Example	ELECTRIC_LOG_OTP_REPORTS=true

ELECTRIC_PORT

Variable	ELECTRIC_PORT
Default	3000
Description	Port that the HTTP API is exposed on.
Example	ELECTRIC_PORT=8080

Caching

ELECTRIC_CACHE_MAX_AGE

Variable	ELECTRIC_CACHE_MAX_AGE
Default	60
Description	Default max-age for the cache headers of the HTTP API.
Example	ELECTRIC_CACHE_MAX_AGE=5

ElECTRIC_CACHE_STALE_AGE

Variable	ELECTRIC_CACHE_STALE_AGE
Default	300
Description	Default stale-age for the cache headers of the HTTP API.
Example	ELECTRIC_CACHE_STALE_AGE=5

Storage

ELECTRIC_PERSISTENT_STATE

Variable	ELECTRIC_PERSISTENT_STATE
Default	FILE
Description	Where to store shape metadata. Defaults to storing on the filesystem. If provided must be one of MEMORY or FILE.
Example	ELECTRIC_PERSISTENT_STATE=MEMORY

ELECTRIC_STORAGE

Variable	ELECTRIC_STORAGE
Default	FILE
Description	Where to store shape logs. Defaults to storing on the filesystem. If provided must be one of MEMORY or FILE.
Example	ELECTRIC_STORAGE=MEMORY

ELECTRIC_STORAGE_DIR

Variable	ELECTRIC_STORAGE_DIR
Default	./persistent
Description	Path to root folder for storing data on the filesystem.
Example	ELECTRIC_STORAGE_DIR=/var/example

Telemetry

ELECTRIC_OTLP_ENDPOINT

Variable	ELECTRIC_OTLP_ENDPOINToptional
Description	Set an OpenTelemetry endpoint URL to enable telemetry.
Example	ELECTRIC_OTLP_ENDPOINT=https://example.com

ELECTRIC_OTEL_DEBUG

Variable	ELECTRIC_OTEL_DEBUG
Default	false
Description	Debug tracing by printing spans to stdout, without batching.
Example	ELECTRIC_OTEL_DEBUG=true

ELECTRIC_HNY_API_KEY

Variable	ELECTRIC_HNY_API_KEYoptional
Description	Honeycomb.io api key. Specify along with HNY_DATASET to export traces directly to Honeycomb, without the need to run an OpenTelemetry Collector.
Example	ELECTRIC_HNY_API_KEY=your-api-key

ELECTRIC_HNY_DATASET

Variable	ELECTRIC_HNY_DATASEToptional
Description	Name of your Honeycomb Dataset.
Example	ELECTRIC_HNY_DATASET=your-dataset-name

ELECTRIC_PROMETHEUS_PORT

Variable	ELECTRIC_PROMETHEUS_PORToptional
Description	Expose a prometheus reporter for telemetry data on the specified port.
Example	ELECTRIC_PROMETHEUS_PORT=9090

ELECTRIC_STATSD_HOST

Variable	ELECTRIC_STATSD_HOSToptional
Description	Enable sending telemetry data to a StatsD reporting endpoint.
Example	ELECTRIC_STATSD_HOST=https://example.com