Running Sync Services

A Sync service is responsible for monitoring changes in data stores, applying necessary transformations, and propagating these changes to consumers as mutation events.

When starting a Sync service, you can supply any number of manifests. The service will be responsible for all Public schemas defined in those manifests. Consumer schemas that reference Public schemas in other manifests can be retrieved over the network from other Sync services.

Prerequisites

• You need to have your manifest(s) ready. For more information, see the Managing Manifests guide.
• You need to have an Event Store deployed and configured in your manifest.

Single Sync Service

If you’re deploying a single Sync service, you can start the service from the rejot-cli and pass all your manifests:

rejot-cli manifest sync rejot-manifest.json another-rejot-manifest.json

Upon startup, the Sync service will verify connections to all data stores and open replication slots to begin monitoring for changes.

Multiple Sync Services

It can be beneficial to set up separate Sync services in cases where you expect high load or you prefer to split service by domain. If you have data dependencies between Sync services, they can exchange data over the network. For this purpose, each Sync service exposes a web server that other Sync services can communicate with.

You can configure the endpoint that a Sync service exposes through the rejot-cli arguments.

To enable external Sync service discovery, you must specify a Resolver that helps the Sync service locate manifest slugs on the network. The simplest resolver is the environment resolver, where you supply a mapping of manifest to hostname through environment variables:

EXPORT REJOT_SYNC_SERVICE_slug-a=sync-service-a:3000

rejot-cli manifest sync rejot-manifest.json \
    --hostname 0.0.0.0 \
    --port 3000 \
    --resolver env

See Composing Manifests for guidance on how to split up your manifests.