Data Flow

Data connections define how outputs from one metaframe become inputs to another. Connections are declared in metapage.json or configured via the metapage editor.

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Connection parameters

A connection has two optional parameters:

1. Source glob — which outputs to forward from the source. Empty or ** means all outputs.
2. Target path — how to name/place the data in the target. Empty means keep the original path.

Output filtering (source glob)

The source glob uses glob pattern matching:

Pattern	Description	Example match
** or empty	All outputs	Everything
*.json	Files with specific extension	data.json but not data/info.json
**/*.json	Extension in any directory	Both data.json and data/info.json
data/*	Files in a specific directory	data/file.txt but not data/sub/file.txt
**/report*	Name pattern in any directory	report.csv, data/report_final.pdf

Filter behavior examples:

Output name	Filter	Forwarded?
any	(empty)	✅
any	**	✅
foo.bar	*.bar	✅
dir1/foo.bar	*.bar	❌
dir1/foo.bar	**/*.bar	✅
dir1/foo.bar	**/foo*	✅

Input mapping (target path)

Type	Definition	Result
Empty	Leave target path empty	Files keep their original names and paths
Directory prefix (ends with /)	e.g. incoming/	Files are placed under that directory in the target
File rename (no trailing /)	e.g. result.csv	Source output is renamed to this name

Full examples

Connection	Source output	Target input	Description
*.json → data/	results.json	data/results.json	Send all JSON to a folder
report.csv → summary.csv	report.csv	summary.csv	Rename a specific file
** → (empty)	data/file.txt	data/file.txt	Pass through unchanged
**/*.csv → reports/	june/sales.csv	reports/june/sales.csv	Nested CSV to folder

Data types by metaframe type

Container (Docker) metaframes

Container inputs and outputs are files:

• Inputs arrive at /inputs/ inside the container ($JOB_INPUTS)
• Outputs are read from /outputs/ when the container exits ($JOB_OUTPUTS)
• Large files are stored in cloud storage; only a reference URL is routed through the message layer

JavaScript metaframes

JavaScript frames send and receive values directly via the metapage module API:

// Receive inputs
export function onInputs(inputs) {
  const value = inputs["myKey"];   // inputs is a plain object
}

// Send a single output
setOutput("result", 42);

// Send multiple outputs
setOutputs({
  result: true,
  data: [1, 2, 3],
});

Supported output types: strings, numbers, booleans, JSON objects/arrays, ArrayBuffer, typed arrays, File, Blob.