SEQUENTIAL_EXECUTOR

When to use

A SEQUENTIAL_EXECUTOR runs a series of functions one at a time, in order. Each step can use the results of the steps before it.

Use SEQUENTIAL_EXECUTOR when your logic requires multiple steps that depend on each other's results. Common use cases include fetching identity data and then using it to retrieve audience segments, running a classification step and then conditionally calling different external services based on the result, and building complex ad request URLs from multiple data sources.

Configuration fields

A SEQUENTIAL_EXECUTOR function has the following fields:

Ordered execution and data flow

MediaTailor runs each step in the sequence from first to last. After each step completes, the values it produces are merged into a running set of results. Subsequent steps can access the original session data plus all values produced by earlier steps.

Temporary data is the primary mechanism for passing data between steps. When a function writes to a temp.* key, the next step can read that value. Player parameters and ad request fields written by earlier steps are also visible to later steps.

Per-step run conditions

Each step in the sequence has an optional RunCondition field. This field contains an expression that returns true or false. MediaTailor evaluates the RunCondition expression immediately before running that step.

If the RunCondition expression evaluates to false, MediaTailor skips the step entirely and moves to the next one. If the RunCondition field is omitted, the step always runs.

{ "FunctionId": "retryFetch", "RunCondition": "{%temp.statusCode = 500%}" }

This mechanism lets you build conditional pipelines. For example, you can run an identity fetch in step 1, then conditionally run a segment lookup in step 2 only if step 1 returned a valid identity.

How the output block works

The output block on a SEQUENTIAL_EXECUTOR controls what the sequence produces after all steps complete:

Timeout configuration

The TimeoutMilliseconds field sets a deadline for the entire sequence. This timeout covers all steps, including any HTTP calls made by functions. If the sequence exceeds the timeout, MediaTailor discards all output from the sequence and proceeds as if no function were attached.

Individual HTTP_REQUEST functions still respect their own RequestTimeoutMilliseconds setting. The sequence timeout acts as an outer boundary that caps the total execution time.

Example: Retry on HTTP failure

This example calls an identity API and automatically retries if the first call returns a server error. It uses two HTTP_REQUEST functions orchestrated by a SEQUENTIAL_EXECUTOR.

Step 1 — Primary fetch (fetchIdentity):

{
    "FunctionId": "fetchIdentity",
    "FunctionType": "HTTP_REQUEST",
    "HttpRequestConfiguration": {
        "Runtime": "JSONATA",
        "MethodType": "GET",
        "Url": "{%'https://identity.example.com/v1/resolve?ip=' & session.client_ip%}",
        "Headers": {
            "Accept": "application/json"
        },
        "RequestTimeoutMilliseconds": 1000,
        "Output": {
            "temp.statusCode": "{%response.statusCode%}",
            "temp.envelope": "{%response.statusCode = 200 ? response.body.envelope : null%}"
        }
    }
}

Step 2 — Retry on failure (retryIdentity):

{
    "FunctionId": "retryIdentity",
    "FunctionType": "HTTP_REQUEST",
    "HttpRequestConfiguration": {
        "Runtime": "JSONATA",
        "MethodType": "GET",
        "Url": "{%'https://identity-fallback.example.com/v1/resolve?ip=' & session.client_ip%}",
        "Headers": {
            "Accept": "application/json"
        },
        "RequestTimeoutMilliseconds": 1000,
        "Output": {
            "temp.statusCode": "{%response.statusCode%}",
            "temp.envelope": "{%response.statusCode = 200 ? response.body.envelope : null%}"
        }
    }
}

Sequence (identityWithRetry):

{
    "FunctionId": "identityWithRetry",
    "FunctionType": "SEQUENTIAL_EXECUTOR",
    "SequentialExecutorConfiguration": {
        "Runtime": "JSONATA",
        "TimeoutMilliseconds": 2000,
        "FunctionList": [
            { "FunctionId": "fetchIdentity" },
            { "FunctionId": "retryIdentity", "RunCondition": "{%temp.statusCode >= 500%}" }
        ],
        "Output": {
            "player_params.envelope": "{%temp.envelope%}"
        }
    }
}

How it works: