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 options are DATABASE_URL and ELECTRIC_SECRET.

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_QUERY_DATABASE_URL

Variable	ELECTRIC_QUERY_DATABASE_URL
Default	DATABASE_URL
Description	Postgres connection string. Used to connect to the Postgres database for anything but the replication, will default to the same as DATABASE_URL if not provided. 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. This can point to a connection pooler and does not need a REPLICATION role as it does not handle the replication. For a secure connection, set the sslmode query parameter to require.
Example	ELECTRIC_QUERY_DATABASE_URL=postgresql://user:password@example-pooled.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_DATABASE_CA_CERTIFICATE_FILE

Variable	ELECTRIC_DATABASE_CA_CERTIFICATE_FILEoptional
Description	The path on local disk to a file containing trusted certificate(s) that Electric will use to verify the database server identity. Trusted certificates are those that have been signed by trusted certificate authorities (CA); they are also known as root certificates. Every operating system and most web browsers include a bundle of well-known root certificates (aka CA store). You can instruct Electric to use the default bundle provided by your OS by specifying an absolute path to it. This page from Neon lists the typical locations for different operating systems. Some managed Postgres providers such as Supabase and DigitalOcean use a self-signed root certificate that won't be found in OS-specific CA stores. If you're using one of those, download the trusted certificate from the provider's website and put it somewhere on your local disk where Electric can access it. Certificate verification and sslmode Electric doesn't support sslmode=verify-ca or sslmode=verify-full query params in DATABASE_URL. Those values are specific to psql. When you configure Electric with a trusted certificate file, it will always try to verify the server identity and will refuse to open a database connection if the verification does not succeed. Note, however, that setting sslmode=disable in DATABASE_URL and enabling certificate verification at the same time will result in a startup error.
Example	ELECTRIC_DATABASE_CA_CERTIFICATE_FILE=/root/.postgresql/root.crt

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_SECRET

Variable	ELECTRIC_SECRETrequired
Description	Secret for shape requests to the HTTP API. This is required unless ELECTRIC_INSECURE is set to true. By default, the Electric API is public and authorises all shape requests against this secret. More details are available in the security guide.
Example	ELECTRIC_SECRET=1U6ItbhoQb4kGUU5wXBLbxvNf

ELECTRIC_INSECURE

Variable	ELECTRIC_INSECURE
Default	false
Description	When set to true, runs Electric in insecure mode and does not require an ELECTRIC_SECRET. Use with caution. API requests are unprotected and may risk exposing your database. Good for development environments. If used in production, make sure to lock down access to Electric.
Example	ELECTRIC_INSECURE=true

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 in 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_TCP_SEND_TIMEOUT

Variable	ELECTRIC_TCP_SEND_TIMEOUT
Default	30s
Description	Timeout for sending a response chunk back to the client. Defaults to 30 seconds. Slow response processing on the client or bandwidth restristrictions can cause TCP backpressure leading to the error message: Error while streaming response: :timeout This environment variable increases this timeout.
Example	ELECTRIC_TCP_SEND_TIMEOUT=60s

ELECTRIC_SHAPE_CHUNK_BYTES_THRESHOLD

Variable	ELECTRIC_SHAPE_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_SHAPE_CHUNK_BYTES_THRESHOLD=20971520

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

These environment variables allow configuration of metric and trace export for visibility into performance of the Electric instance.

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

Logging

ELECTRIC_LOG_LEVEL

Variable	ELECTRIC_LOG_LEVELoptional
Description	Verbosity of Electric's log output. Available levels, in the order of increasing verbosity: error warning info debug
Example	ELECTRIC_LOG_LEVEL=debug

ELECTRIC_LOG_COLORS

Variable	ELECTRIC_LOG_COLORSoptional
Description	Enable or disable ANSI coloring of Electric's log output. By default, coloring is enabled when Electric's stdout is connected to a terminal. This may be undesirable in certain runtime environments, such as AWS which displays ANSI color codes using escape sequences and may incorrectly split log entries into multiple lines.
Example	ELECTRIC_LOG_COLORS=false

ELECTRIC_LOG_OTP_REPORTS

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

Usage reporting

ELECTRIC_USAGE_REPORTING

These environment variables allow configuration of anonymous usage data reporting back to https://electric-sql.com

Variable	ELECTRIC_USAGE_REPORTING
Default	true
Description	Configure anonymous usage data about the instance being sent to a central checkpoint service. Collected information is anonymised and doesn't contain any information from the replicated data. You can read more about it in our telemetry docs.
Example	ELECTRIC_USAGE_REPORTING=true