Supermetal Documentation

Push data changes to HTTP endpoints in Debezium or Supermetal format.

Batching: Combine rows into JSON arrays
Compression: Gzip, Zstandard, or Brotli
Rate limiting: Limit requests/second and bytes/second
Idempotency: Deterministic keys for exactly-once delivery

Message Formats

Debezium or Supermetal. See Kafka Message Formats.

Request Format

POST /webhooks/public/orders HTTP/1.1
Content-Type: application/json
Content-Encoding: gzip
Idempotency-Key: 019c4ab1-473b-783c-af83-b22a9aa26cff
X-Source-Schema: public
X-Source-Table: orders

[
    {"id": 1, "name": "Alice", "_sm_version": 1234, "_sm_deleted": false},
    {"id": 2, "name": "Bob", "_sm_version": 1235, "_sm_deleted": false}
]

Prerequisites

HTTP endpoint that accepts POST with application/json
Authentication credentials (if required)

Setup

Endpoint

URL: Base endpoint (e.g., https://api.example.com/events)
Path Template: Append path with {schema} and {table} placeholders

Example: https://api.example.com + webhooks/{schema}/{table} → https://api.example.com/webhooks/public/users

Authentication (optional)

Method	Header
Bearer	`Authorization: Bearer <token>`
Basic	`Authorization: Basic <base64(user:pass)>`
Header	Custom name/value (e.g., `X-API-Key: secret`)

Message Format

Debezium or Supermetal — see Kafka Message Formats.

Headers

Header	Default	Description
`Idempotency-Key`	on	Deterministic deduplication key
`X-Source-Schema`	on	Source schema name
`X-Source-Table`	on	Source table name

Configure header names or disable individually.

Idempotency Key

Derived from source table, row identity, and commit timestamp. Retrying the same batch produces the same key. Keys are time-sortable.

For predictable idempotency, keep batch configuration stable. Disable batching (Max Batch Size = 1) for per-row keys.

Static Headers

Add custom headers to every request.

Batching

Option	Default	Description
Max Batch Size	`0` (unlimited)	Rows per request
Max Payload Bytes	`1 MB`	Request body size

Flushes when either limit triggers. Set Max Batch Size = 1 to disable batching.

Compression

Value	Content-Encoding
None	—
Gzip	`gzip`
Zstd	`zstd`
Br	`br`

Rate Limiting

Option	Default	Description
Max Requests/Second	`0` (unlimited)	Request rate
Max Bytes/Second	`0` (unlimited)	Bandwidth

Retry

Exponential backoff with jitter.

Option	Default	Description
Max Retries	`1024`	Attempts (`0` = unlimited)
Max Retry Duration	`1 hour`	Total time (`0` = unlimited)
Initial Backoff	`1s`	First delay
Max Backoff	`3 min`	Maximum delay

Timeouts

Option	Default
Request Timeout	`30s`

Webhook