AshHooks

Receive, verify, and deduplicate incoming webhooks. Sign, deliver, retry, and track outgoing webhooks with Ash Framework.

A ledger is a database table that records delivery identity, state, and outcome. Deduplication uses a unique index to retain one row per identity.

Inbound and outbound work independently. Inbound needs no queue. Outbound can use the generated Oban worker or your own scheduler calling AshHooks.Delivery.run/2.

Requires Elixir ~> 1.20, Erlang/OTP 28 or 29, and Ash >= 3.37.2 and < 4.0.0-0. Add {:ash_hooks, "~> 3.1"} to your dependencies. Oban ~> 2.20 is optional and required for the generated worker. Plug ~> 1.16 is optional for HTTP receipt. Every supported Ash version requires your application to set default_string_length_count; see UPGRADING.md.

The get-started tutorial includes migrations, resources, a provider, domain registration, and executable calls. The Livebook walks through both directions with real SQLite and a real request-capture receiver.

Receiving webhooks

A provider describes a signing contract. This application-defined example checks a lowercase hexadecimal HMAC-SHA256 signature over timestamp.body. HMAC means hash-based message authentication code. Any valid v1 signature in the structured header is accepted, allowing the sender to rotate keys. The timestamp must be within 300 seconds of the clock.

defmodule MyApp.Webhooks.Payments do
  use AshHooks.Provider,
    verify: [
      algorithm: :hmac_sha256,
      signature: {:structured_header, "x-payments-signature", signature_key: "v1"},
      timestamp: {:signature_field, "t"},
      signed_input: [:timestamp, ".", :body],
      tolerance_seconds: 300
    ]
end

Declare the provider explicitly on an inbound ledger; the source name does not select a module. Keep the name stable because it is part of the delivery identity. A secret source can be an {module, function, args} callback, {:app_env, path}, a zero-argument function, or a tenant-aware one-argument function. Literal secret strings are rejected. For public-key schemes the source returns the public key.

Providers support HMAC, RSA, ECDSA (elliptic curve digital signature algorithm), Ed25519, and JWS (JSON Web Signature) bodies. Headers can contain a single signature or several structured signatures. The verification guide explains encodings, signed input, timestamps, rotation, and custom callbacks. ash_hooks includes no vendor-specific verifiers; use the sender's signing documentation.

Mounting the plug

Configure the raw-body reader in your Phoenix endpoint before the router. This fragment is tested inside a complete endpoint and router with a real SQLite ledger.

plug Plug.Parsers,
  parsers: [:json],
  pass: ["*/*"],
  body_reader: {AshHooks.BodyReader, :read_body, []},
  json_decoder: Phoenix.json_library()

mix igniter.install ash_hooks attempts to add this reader. Review the result. Pass [only: ["/webhooks"]] as the reader's third element to cache only webhook routes. An existing body reader can call AshHooks.BodyReader.put_raw_body/2 with the complete bytes before parsing. Never reconstruct signed bytes from params.

The following endpoint/router fragments form one tested application example. Use a fixed source only for a single-tenant ledger without scope fields.

# MyAppWeb.Endpoint, before the router
plug Plug.Parsers,
  parsers: [:urlencoded, :multipart, :json],
  pass: ["*/*"],
  json_decoder: Jason,
  body_reader: {AshHooks.BodyReader, :read_body, [only: ["/webhooks"]]}

# MyAppWeb.Router
forward "/webhooks/payments", AshHooks.Plug,
  resource: MyApp.WebhookLedger,
  source: :payments,
  request_uri: "https://hooks.example.com"

The plug verifies, stores the decoded payload and signed-byte digest, deduplicates, claims the row under a time-limited ownership token, runs the handler, and records the result. Configure it outside browser/session/CSRF pipelines. Default responses:

Default 503s include retry-after: 60; configure retry_after: to change it. POST is the default method. Direct reads allow 8,000,000 bytes by default; preceding parsers have their own limits. Missing or repeated signature headers yield an unsigned-request error. With ingress_tracking :on, rejected requests may store one digest row per source, scope, and body, rather than one row per request.

For a scoped or multitenant ledger, use resolve: {module, function, args} to look up a stored endpoint and return source, tenant, scope, and connection. Never trust path strings as tenants or convert them into module names. The scope keys must match scope_identity; include them in the database unique index.

request_uri: accepts a configured public base URL or a callback returning the full public URI. It never trusts the connection's internal host, scheme, or port. A provider reading ctx.signature needs signature_header: on the plug or resolver. Configured providers read their own headers and need no such option.

Provider handshake/1 can answer challenges before method and signature checks. Response precedence is provider response/1, then the plug's respond: callback, then AshHooks.Plug.default_response/2. A refuse: callback can customize refusal headers and body while preserving the status and required headers.

Handling and identity

Configured providers return a :webhook event. Override parse_event_type/1 and handle_event/2 to run application actions. Use a fixed event-name table; never turn request data into new atoms. Return {:ok, result}, {:error, :retry, reason}, or {:error, :permanent, reason}. Exceptions, exits, and throws are contained and recorded as retryable failures with error class "handler_crashed".

Handlers run at least once. A crash after a business effect and before recording success can repeat the handler. Make the business effect idempotent, keyed on the logical event identity. Terminal rows are never processed again.

An explicit event_id extractor takes precedence. Invalid extractor results use the raw-body digest. Otherwise event_identity/1 is used when implemented; invalid provider identities fail ingestion. With neither callback, identity is the SHA-256 of the raw body. JWS providers hash canonical JSON of the verified payload.

JSON is the default. body_format :form opts a route into flat URL-encoded form decoding. Verification always sees exact raw bytes first. previous_secret allows both inbound keys until you remove it; paused refuses ingestion before verification. AshHooks.Ingress.list/2 and counts/2 expose inbound state.

For HTTP Message Signatures (RFC 9421), use RequestSeal with {:request_seal, "~> 1.0"}. Its adapter integrates verification with a provider. Configure a nonce replay store when signatures must be accepted only once; ledger deduplication alone is a different guarantee. See the verification guide.

Sending webhooks

Declare an outbound event, endpoint resource, subscription resource, and delivery resource. Dispatch stores exact payload bytes once per endpoint and event ID. Without an enqueue callback, deliveries stay pending. The tutorial shows a generated worker; set oban: to the supervised instance name or omit it for the default Oban.

Delivery succeeds on 2xx, retries 408/429/5xx and transport failures, refuses redirects, and permanently fails other client errors. Retry-After is bounded; otherwise retries use exponential backoff with random delay. A 410 stores a pending disable obligation, conditionally disables the matching endpoint configuration, and completes the delivery. Subscribe to disable telemetry so operators can act. A hostname that stops resolving retries as nxdomain or resolve_timeout; a validated private or loopback address fails permanently.

The delivery row controls retry counts and timing. Oban provides a durable trigger. Set all budgets to positive integers. Compilation checks positive integer attempt, finalization, delivery-attempt, backoff, and Retry-After budgets, backoff ordering, timeout relationships, and the Oban attempt ceiling. Runtime settings are validated before delivery; invalid settings fail the job without changing the row.

Schedule AshHooks.reconcile_pending/3 per declaration and tenant with the same queue callback used at dispatch. It recovers enqueue gaps, due retries, expired send leases, and pending disables while preserving retry timing and attempt counts. Anonymous callbacks need a stable enqueue_key for recovery. Synchronize node clocks because leases use application UTC time. Network delivery remains at least once; receivers deduplicate using the stable webhook-id.

Optional outbound features

• retryable_statuses replaces the ordinary retry set. Success, redirects, and the 410 rule stay fixed. delivery_headers adds checked metadata headers; signing, content type, and framing headers cannot be overridden.
• certificate_pin adds a certificate or public-key digest check to HTTPS using the bounded adapter. AshHooks.DestinationPolicy can allow or deny destinations. AshHooks.Transport supplies another transport with the same signing and retries.
• AshHooks.OutboundAttempt records attempt history, including the real request duration and signing-key reference for HTTP 410 responses. History-write failures emit telemetry without undoing the delivery's completed result transition.
• Response snippets contain status and content-type summaries by default. Endpoint opt-in captures bounded, redacted history bodies. A direct diagnostic run with snippet_capture: true can capture on the delivery row. For retryable failures, wait until due; for terminal rows, call resend/2 before running again.
• test_send/2 sends outside subscriptions, using :signing_mode (default :standard). resend/2 re-arms terminal deliveries. Bulk replay counts a limited batch in dry run; repeated calls can select skipped rows again and return no cursor.
• :standard signing uses secret_ref. :legacy and :dual also need legacy_secret_ref. References resolve through your secret store.
• Key rolling keeps both keys signing until previous_secret_ref is cleared. Schedule AshHooks.Endpoint.expire_previous_secrets/2. The retirement timestamp records the actual removal time, including early retirement.
• Endpoint health uses recorded durations, including failed attempts. Eventual successes include first-attempt successes. Explicit time bounds need :from. Supplying :to without :from returns {:error, :from_required}. Health sweeps enforce warning_interval_seconds (default 60) from the stored warning time, including overlapping sweeps. Counts and telemetry confirm successful writes.
• Catalog metadata and payload versions describe events. Subscription attribute filters match event metadata. An event log preserves events even with no enabled endpoints. Replay takes declaration: {Emitter, :event_name} and binds each new delivery to that declaration and enqueue callback. Enable resend_tracking :on to store the requester and request time. Enqueue receives (delivery, event), matching the generated worker and recovery contracts. Terminal replay forwards the tenant to resend.

Fitting the extensions to your domain

payload_attribute renames a ledger's byte column. prune_action :none prevents injection of the :prune destroy action; it leaves application-defined destroy actions intact. Endpoint status mapping can use an existing enable switch. Subscription event types may be constrained atoms or strings; both match the same names. An application declaration replaces the generated attribute and its defaults.

Ledger state transitions use the complete primary key, including custom or composite keys. Paginated queries additionally require an :id attribute. Endpoint and subscription references require a single UUID-compatible key, including UUIDv7. A full last page still carries a cursor; a shorter page carries nil.

Multi-tenancy

Declare consistent attribute multitenancy on every enabled resource, including attempt history and the event log. Pass the tenant to every entry point and include the tenant in unique indexes. AshHooks.Tenancy.resolve/2 validates only the modules supplied by each caller. Entry points include every resource they touch, including optional history and event logs, and reject mismatches before data access.

The generated worker carries the tenant in job args. String tenants are supported; custom parsing must have a matching tenant_from_attribute inverse. Tenant-aware secret resolvers receive both reference and tenant. When adopting tenancy on populated tables, backfill every tenant value, rebuild identities, and only then enable tenant traffic. The checklist gives the ordered transition for every tenant.

Retention and security

Your application schedules retention and controls read access. Inbound pruning deletes :processed, :failed_permanent, and :superseded rows; it excludes tracked :failed_verification rows, which need a separate policy. Delivery pruning deletes terminal deliveries and their history in one transaction when attempts: is provided. History-deletion errors roll back the batch and are returned. Both resources must support transactions; for SQLite, enable write_transactions?/0 on the repo. Add inserted_at and a matching migration. Deletion reopens deduplication identities, so retain rows beyond the sender's replay period.

HMAC comparisons use constant time after a length check; public-key verification uses OTP cryptographic functions. Destination checks defend against server-side request forgery. Default adapters connect to validated addresses, and the bounded adapter limits reads and elapsed time. Built-in capture redaction recognizes specific secret patterns; add rules for application-sensitive values.

The package injects machine write actions and no read policies. Restrict exposed actions and define read policies for payload-bearing resources. Internal operations bypass authorization and must only be called by trusted application code. Report vulnerabilities privately through SECURITY.md.

Observability and stability

AshHooks.Telemetry lists all event names and metadata. Attach exact names using attach_many; events omit payloads, bodies, and signing secrets. The tutorial's handler shows the basic lifecycle; the module reference includes optional events.

The public contract includes the DSL, public functions, injected attributes and actions, telemetry, and error classes. Breaking changes next ship in 4.0.0; deprecations run at least two minor releases. Safety corrections can change defective behavior in patch releases and are described in the CHANGELOG. Development supports macOS and Linux; use WSL2 on Windows.

Upgrading from before 3.0.0 removes built-in vendor providers and requires explicit providers. UPGRADING.md explains names, identities, schemas, and versions. See CONTRIBUTING.md, the DSL reference, and the API reference for more.

License

MIT.