- Interacting with REST APIs which assign each record its own resource path
- Using different HTTP methods based on the change action
- Implementing custom routing logic based on record contents
- Customizing message routing for various messaging systems
How routing functions work
When you create a routing function, you define an Elixir function that returns routing information. Sequin will use this information to determine the destination for each message. For each message, your routing function receives the same parameters as a transform function and must return a map containing the sink-specific routing information:Sinks
Each sink type has different fields that can be routed:Kafka sink
For Kafka, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
topic | String | The topic to publish to | "users.created" |
message_key | String | The message key to publish to | "users:123" |
HTTP Webhook sink
For HTTP webhooks, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
method | String | The HTTP method to use | "POST" , "PUT" , "DELETE" |
endpoint_path | String | The path to append to your webhook base URL | "/users/123" |
endpoint_path
you specify will be appended to the base URL of your webhook endpoint. For example, if your webhook endpoint is https://api.example.com
and your routing function returns endpoint_path: "/users/123"
, the message will be sent to https://api.example.com/users/123
.
Redis String sink
For Redis String, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
key | String | The key to use for the message | "users:123" |
key
is used to determine the key in Redis where the message will be stored in the SET
operation:
Redis Stream sink
For Redis Stream, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
stream_key | String | The stream key to publish to | "users" |
NATS sink
For NATS, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
subject | String | The subject to publish to | "users.created" |
GCP PubSub sink
For GCP PubSub, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
topic_id | String | The topic ID to publish to | "users.created" |
Elasticsearch sink
For Elasticsearch, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
index_name | String | The index to publish to | "users" |
Typesense sink
For Typesense, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
action | String | The action to perform on the collection | "index" , "delete" |
collection_name | String | The collection name to index into | "users" |
Meilisearch sink
For Meilisearch, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
action | String | The action to perform on the collection | "index" , "delete" |
index_name | String | The index to publish to | "users" |
AWS SQS sink
For AWS SQS, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
queue_url | String | The queue URL to publish to | "https://sqs.us-east-1.amazonaws.com/123456789012/users" |
AWS Kinesis sink
For AWS Kinesis, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
stream_arn | String | The Kinesis stream ARN to publish to | "arn:aws:kinesis:us-east-1:123456789012:stream/my-stream" |
S2 sink
For S2, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
basin | String | The S2 basin to publish to | "my-basin" |
stream | String | The S2 stream to append records to | "users" |
RabbitMQ sink
For RabbitMQ, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
exchange | String | The exchange to publish to | "sequin" |
routing_key | String | The routing key to publish to | "sequin.users.insert" |
headers | Map | AMQP headers to include | %{"x-key" => "value"} |
Azure Event Hub sink
For Azure Event Hubs, your routing function must return a map with these keys:Key | Type | Description | Example |
---|---|---|---|
event_hub_name | String | The Event Hub name to publish to | "sequin.db.public.users" |
Common routing patterns
Routing to REST APIs
Route messages to RESTful endpoints based on record ID and action:Content-based routing
Route messages based on their content:Testing routing functions
When creating or editing a routing function, you can test it with real data from your database. Sequin will capture recent events and show you the effective routing parameters for each message. “Effective” means that Sequin will show the routing parameters that will actually be used downstream, inclusive of any defaulting or validation which happens after your routing function runs.Limitations and considerations
- Routing can impact batching if your routing function generates different destinations for each message.
Related
Function Transforms
Learn about function transforms and how to use them to modify your message content.
Messages reference
Learn about the different fields you can use in routing functions.
Sequin YAML config
Learn about configuring functions in your sequin.yaml file.
HTTP Webhooks
Learn more about configuring HTTP webhook destinations.