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specs/039-wait.md

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# Spec: Wait Actions

## Status

Implemented.

This spec defines conformance behavior for the built-in `wait.duration`,
`wait.until`, `wait.file`, and `wait.http` actions.

## Scope

This spec defines four actions that block a step until a condition becomes
true, then succeed:

- `wait.duration`: waits for a fixed length of time.
- `wait.until`: waits until an absolute point in time.
- `wait.file`: polls a filesystem path until it exists or stops existing.
- `wait.http`: polls an HTTP URL until it returns an expected status.

This spec covers:

- the `with` fields each action accepts, and their defaults
- how each action determines the condition is satisfied
- validation and runtime errors
- how these actions interact with a step's own `timeout_sec`

This spec does not define:

- signal delivery and abort behavior beyond what already applies to any step
  (see [Spec 017: Built-In Run Context](017-built-in-run-context.md))
- retry or `precondition` behavior
- authentication for `wait.http` requests

## Goal

Workflow authors pause a DAG-run until an external condition holds --
a fixed delay, a wall-clock deadline, a file appearing or disappearing, or
an HTTP endpoint becoming ready -- without writing a polling script by hand.

## Behavior

### wait.duration

`with.duration` (required) is a Go-style duration string (for example
`30s`, `5m`) and must be greater than zero. The step blocks for that long,
then succeeds.

### wait.until

`with.until` (required) is either an RFC3339 timestamp or a `HH:MM[:SS]`
clock time. The step blocks until the resolved deadline, then succeeds.

A clock time resolves on the run's logical day, in `with.timezone` when
set, otherwise in the run-configured zone. The logical day is the date of
`context.run.scheduled_at` when the run has one, and retries of that run
keep it; otherwise it is the date of `context.attempt.started_at`, so a
retry of a manual run that starts on a later day resolves on that day. A
clock time never rolls over to the next day. As in RFC 5545, a clock time
that a daylight-saving transition skips is read with the UTC offset in
effect before the gap, so `02:30` on the night `America/New_York` springs
forward resolves to `03:30` EDT, and a clock time that a transition repeats
resolves to its first occurrence. `with.timezone` applies only to clock
times and is ignored for RFC3339 timestamps. `with.offset` (a duration,
may be negative) shifts the resolved deadline.

`with.if_past` selects behavior, for both forms, when the deadline is
already past as the step starts: `continue` (default) succeeds
immediately, `fail` errors, and `window` succeeds when the deadline passed
no more than `with.window` ago and otherwise errors. `with.offset`,
`with.timezone`, `with.if_past`, and `with.window` are only valid on
`wait.until`.

### wait.file

`with.path` (required) is a file or directory path, resolved relative to
the step's working directory when not absolute. `with.state` selects the
condition:

- `exists` (default): succeeds once something exists at that path.
- `missing`: succeeds once nothing exists at that path.

The action polls at `with.poll_interval` (default `1s`).

### wait.http

`with.url` (required) must be an absolute `http://` or `https://` URL.
`with.method` defaults to `GET`. `with.headers` and `with.body` set the
request's headers and body. The action polls at `with.poll_interval`
(default `1s`), giving each individual request `with.request_timeout`
(default `10s`) to complete. A request that fails outright (connection
refused, timeout, and similar) counts as a non-matching poll rather than an
error and is retried on the next interval. The step succeeds once a
response's status code equals `with.status` (default `200`).

Config-schema validation for `with.url` (and `with.status`) accepts a value
that holds a `${...}` or `$VAR` reference anywhere in it, such as
`${BASE_URL}/health`, and leaves its strict check to run time, once the
reference has resolved; a literal (non-reference) value is still validated
strictly at build time.

`with.headers` and `with.body` are sent exactly as given, with no scheme
enforcement: a `with.url` using `http://` sends them in cleartext the same
as any other `http://` request. A workflow author who puts a credential in
`with.headers` is responsible for using an `https://` URL.

### Interaction with timeout_sec

All four actions poll or sleep against the step's own context, so a step
`timeout_sec` set on any of them cancels the wait once it elapses, the same
way it cancels any other step.

## Errors

### Validation

All of the following are rejected by DAG-build-time validation, before the
DAG starts running. A `with` value that holds an unescaped `${...}` or `$VAR`
reference anywhere in it defers its strict check to run time, once the
reference has resolved; only literal values, including those whose `$` is
escaped as `\$`, are rejected here. A value that still holds a reference at
run time and fails its check is reported as holding an unresolved reference:

- `wait.duration`: `with.duration` is empty, is not a parseable duration, or
  is not greater than zero.
- `wait.until`: `with.until` is empty or is neither a valid RFC3339 timestamp
  nor a valid `HH:MM[:SS]` clock time; `with.timezone` is not an IANA name;
  `with.offset` is not a duration; `with.if_past` is not `continue`, `fail`,
  or `window`; `with.window` is not a duration greater than zero, is set
  without `if_past: window`, or is missing with `if_past: window`.
  `with.offset`, `with.timezone`, `with.if_past`, or `with.window` set on
  any other action.
- `wait.file`: `with.path` is empty, or `with.state` is a value other than
  `exists` or `missing`.
- `wait.http`: `with.url` is empty or is not an absolute `http://`/`https://`
  URL, or `with.status` is outside `100`-`599`.

### Timeout and abort

All four actions block by sleeping or polling against the step's own
context (see "Interaction with timeout_sec" above), so a step `timeout_sec`
elapsing, or the DAG-run being stopped (`dagu stop` or an equivalent
cancellation), cancels the wait immediately with the same step-timeout or
abort result any other step gets; none of these actions has its own
distinct timeout or abort error shape.

### Cleanup

None of the four actions creates an external resource (a container, a job,
a connection held open past the request) that needs cleanup on completion,
failure, timeout, or abort. A `wait.http` request in flight when the step
is cancelled is simply abandoned; the action does not need to release
anything afterward.

## Related Specs

- Run context: [Spec 017: Built-In Run Context](017-built-in-run-context.md)
- Value resolution: [Spec 003: Value Resolution and Field Evaluation](003-value-resolution.md)

## Examples

Wait for a fixed delay:

```yaml
steps:
  - action: wait.duration
    with:
      duration: 30s
```

Wait for a file to appear, polling every 500ms:

```yaml
steps:
  - action: wait.file
    with:
      path: ready.flag
      poll_interval: 500ms
```

Wait for an HTTP health check to return 200:

```yaml
steps:
  - action: wait.http
    with:
      url: http://localhost:8080/healthz
      poll_interval: 1s
```