# Trigger Workflow Run

> Start a new workflow run.

## Endpoint

`POST https://qstash-{region}.upstash.io/v2/trigger/{workflowUrl}`

## Parameters

- `workflowUrl` (path, string, required): The URL of the workflow to trigger.
- `Upstash-Workflow-RunId` (header, string): Optional custom run ID for the workflow run. A random ID will be generated if not provided.
- `Upstash-Forward-*` (header, string): You can send custom headers to your workflow.

To send a custom header, prefix the header name with `Upstash-Forward-`. We will strip prefix and send them to the destination.

| Header | Forwarded To Destination As |
|--------|--------------|
| Upstash-Forward-My-Header: my-value | My-Header: my-value |
| Upstash-Forward-Authorization: Bearer <token> | Authorization: Bearer <token> |

- `Upstash-Retries` (header, integer): Number of retries for the workflow steps in case of failure.
- `Upstash-Delay` (header, string): Delay the message delivery.

The format of this header is `<value><unit>` where value is a number and unit is one of:
- `s` for seconds
- `m` for minutes
- `h` for hours.
- `d` for days.

- `Upstash-Not-Before` (header, integer): Delay the message delivery until a certain timestamp in the future.

The format is a unix timestamp in seconds, based on the UTC timezone.

When both `Upstash-Not-Before` and `Upstash-Delay` headers are provided, `Upstash-Not-Before` will take precedence.

- `Upstash-Label` (header, string): Optional label(s) to attach to the workflow run for easier identification in logs and DLQ.

You can assign multiple labels by providing a comma-separated list.

Example: `label_1,label_2`

- `Upstash-Flow-Control-Key` (header, string): Flow control key to manage concurrency for the workflow run. Steps with the same key will respect the same concurrency limit.
Make sure you pass `Upstash-Flow-Control-Value` header as well to define the limits for the key.
- `Upstash-Flow-Control-Value` (header, string): Parallelism and rate limit configuration for the flow control key in the format:
 `parallelism=<value>, rate=<value>, period=<value>`.
See [flow control](/workflow/features/flow-control) for details.

- `Upstash-Failure-Callback` (header, string): Failure callback URL to be called if the workflow run fails after all retries. That is when all the defined retries are exhausted. To call the failure function defined on server, this options should be left empty. A url should be given with this header only to call a different endpoint on failure. See [failureUrl](https://upstash.com/docs/workflow/features/failureFunction/advanced).

- Failure callback URL must be prefixed with a valid protocol (http:// or https://)
- Failure callbacks are charged as a regular message.
- Failure callbacks will use the retry setting from the original request.

- `Upstash-Failure-Callback-Forward-*` (header, string): You can send custom headers along with your failure callback message.
To send a custom header, prefix the header name with `Upstash-Failure-Callback-Forward-`. We will strip prefix and them to the failure callback URL.

| Header | Forwarded To Callback Destination As |
|--------|--------------|
| Upstash-Failure-Callback-Forward-My-Header: my-value | My-Header: my-value |
| Upstash-Failure-Callback-Forward-Authorization: Bearer <token> | Authorization: Bearer <token> |

- `Upstash-Retry-Delay` (header, string): Customize the delay between retry attempts when step delivery fails.

By default, Upstash Workflow uses [exponential backoff](/qstash/features/retry). You can override this by providing a mathematical expressions to compute next delay. This expression is computed after each failed attempt.

You can use the special variable `retried`, which is how many times the message has been retried. The `retried` is 0 for the first retry.

Supported functions: 
| Function    | Description                          |
|-------------|--------------------------------------|
| `pow(x, y)`| Returns x raised to the power of y|
| `exp(x)`| Returns e raised to the power of x|
| `sqrt(x)`| Takes the square root of x|
| `abs(x)`| Returns the absolute value of x|
| `floor(x)`| Returns the largest integer less than or equal to x|
| `ceil(x)`| Returns the smallest integer greater than or equal to x|
| `round(x)`| Rounds x to the nearest integer|
| `min(x, y)`| Returns the smaller of x and y|
| `max(x, y)`| Returns the larger of x and y|

Examples:
- `1000`: Fixed 1 second delay
- `1000 * (1 + retried)`: Linear backoff
- `pow(2, retried) * 1000`: Exponential backoff
- `max(1000, pow(2, retried) * 100)`: Exponential with minimum 1s delay


## Request body


## Responses

### 200 - Workflow triggered successfully

- `workflowRunId` (string): The ID of the triggered workflow run.
- `workflowCreatedAt` (number): The timestamp when the workflow run was created.

### 400 - Bad Request

- `error` (string, required): Error message

### 401 - Unauthorized

- `error` (string, required): Error message

### 500 - Internal Server Error

- `error` (string, required): Error message

## cURL

```bash
curl --request POST \
  --url https://qstash-{region}.upstash.io/v2/trigger/{workflowUrl} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: text/plain' \
  --data '<string>'
```