Contents

• Key concepts in this topic

• Inline Map state fields

• Deprecated fields

• Inline Map state example (JSONPath)

• Inline Map state example with ItemSelector

• Inline Map state input and output processing

Inline mode

A limited-concurrency mode of theMap state. In this mode, each iteration of theMap state runs in the context of the workflow that contains theMap state. Step Functions adds the execution history of these iterations to the parent workflow's execution history.Map states run in the Inline mode by default.

This mode accepts only a JSON array as input and supports up to 40 concurrent iterations.

Inline Map state

AMap state set to theInline mode.

Map workflow

The set of steps that theMap state runs for each iteration.

Map state iteration

A repetition of the workflow defined inside of theMap state.

Type (Required)

Sets the type of state, such asMap.

ItemProcessor (Required)

Contains the following JSON objects that specify theMap state processing mode and definition.

The definition contains the set of steps to repeat for processing each array item.

• ProcessorConfig – An optional JSON object that specifies the processing mode for theMap state. This object contains theMode sub-field. This field defaults toINLINE, which uses theMap state in Inline mode.

  In this mode, the failure of any iteration causes theMap state to fail. All iterations stop when theMap state fails.

• StartAt – Specifies a string that indicates the first state in a workflow. This string is case-sensitive and must match the name of one of the state objects. This state runs first for each item in the dataset. Any execution input that you provide to theMap state passes to theStartAt state first.

• States – A JSON object containing a comma-delimited set ofstates. In this object, you define theMap workflow.

  Note

  • States within theItemProcessor field can only transition to each other. No state outside theItemProcessor field can transition to a state within it.

  • TheItemProcessor field replaces the now deprecatedIterator field. Although you can continue to includeMap states that use theIterator field, we highly recommend that you replace this field withItemProcessor.

    Step Functions Local doesn't currently support theItemProcessor field. We recommend that you use theIterator field with Step Functions Local.

Items (Optional, JSONata only)

A JSON array or a JSONata expression that must evaluate to an array.

ItemsPath (Optional, JSONPath only)

Specifies areference path using theJsonPath syntax. This path selects the JSON node that contains the array of items inside the state input. For more information, seeItemsPath (Map, JSONPath only).

ItemSelector (Optional)

Overrides the values of the input array items before they're passed on to eachMap state iteration.

In this field, you specify a valid JSON that contains a collection of key-value pairs. These pairs can contain any of the following:

• Static values you define in your state machine definition.

• Values selected from the state input using apath.

• Values accessed from thecontext object.

For more information, seeItemSelector (Map).

TheItemSelector field replaces the now deprecatedParameters field. Although you can continue to includeMap states that use theParameters field, we highly recommend that you replace this field withItemSelector.

MaxConcurrency (Optional)

Specifies an integer value that provides the upper bound on the number ofMap state iterations that can run in parallel. For example, aMaxConcurrency value of 10 limits theMap state to 10 concurrent iterations running at one time.

In JSONata states, you can specify a JSONata expression that evaluates to an integer.

Note

Concurrent iterations may be limited. When this occurs, some iterations won't begin until previous iterations are complete. The likelihood of this occurring increases when your input array has more than 40 items.

To achieve a higher concurrency, considerDistributed mode.

The default value is0, which places no limit on concurrency. Step Functions invokes iterations as concurrently as possible.

AMaxConcurrency value of1 invokes theItemProcessor once for each array element. Items in the array are processed in the order of their appearance in the input. Step Functions doesn't start a new iteration until it completes the previous iteration.

MaxConcurrencyPath (Optional, JSONPath only)

If you want to provide a maximum concurrency value dynamically from the state input using a reference path, useMaxConcurrencyPath. When resolved, the reference path must select a field whose value is a non-negative integer.

Note

AMap state cannot include bothMaxConcurrency andMaxConcurrencyPath.

ResultPath (Optional, JSONPath only)

Specifies where in the input to store the output of theMap state's iterations. The Map state then filters the input as specified by theOutputPath field, if specified. Then, it uses the filtered input as the state's output. For more information, seeInput and Output Processing.

ResultSelector (Optional, JSONPath only)

Pass a collection of key value pairs, where the values are either static or selected from the result. For more information, seeResultSelector.

Tip

If the Parallel or Map state you use in your state machines returns an array of arrays, you can transform them into a flat array with theResultSelector field. For more information, seeFlattening an array of arrays.

Retry (Optional)

An array of objects, called Retriers, that define a retry policy. States use a retry policy when they encounter runtime errors. For more information, seeState machine examples using Retry and Catch.

Note

If you define Retriers for theInline Map state, the retry policy applies to allMap state iterations, instead of only failed iterations. For example, yourMap state contains two successful iterations and one failed iteration. If you have defined theRetry field for theMap state, the retry policy applies to all threeMap state iterations instead of only the failed iteration.

Catch (Optional)

An array of objects, called Catchers, that define a fallback state. States run a catcher if they encounter runtime errors and either don't have a retry policy, or their retry policy is exhausted. For more information, seeFallback States.

Output (Optional, JSONata only)

Used to specify and transform output from the state. When specified, the value overrides the state output default.

The output field accepts any JSON value (object, array, string, number, boolean, null). Any string value, including those inside objects or arrays, will be evaluated as JSONata if surrounded by{% %} characters.

Output also accepts a JSONata expression directly, for example: "Output": "{% jsonata expression %}"

For more information, seeTransforming data with JSONata in Step Functions.

Assign (Optional)

Used to store variables. TheAssign field accepts a JSON object with key/value pairs that define variable names and their assigned values. Any string value, including those inside objects or arrays, will be evaluated as JSONata when surrounded by{% %} characters

For more information, seePassing data between states with variables.

Iterator

Specifies a JSON object that defines a set of steps that process each element of the array.

Parameters

Specifies a collection of key-value pairs, where the values can contain any of the following:

• Static values that you define in your state machine definition.

• Values selected from the input using apath.

• Repeat actions with Inline Map

• Processing input and output in Step Functions

• ItemsPath (Map, JSONPath only)

• Context object data for Map states

• Repeat actions with Inline Map

• Inline Map state example with ItemSelector

• Processing input and output in Step Functions

• Context object data for Map states

• Process data from a queue with a Map state in Step Functions