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AppSync Resolver

Direct Lambda Resolvers
With Direct Lambda Resolvers, you can circumvent the use of VTL mapping templates when using AWS Lambda data sources.
Amplify GraphQL direct @function
The Amplify @function directive allows you to quickly & easily configure a AWS Lambda resolvers with your GraphQL API.

Event driven, invoked synchronously.

Note

AppSync Resolver Events can come in various shapes this data class supports both Amplify GraphQL directive @function and Direct Lambda Resolver

Limits

  • Request execution timeout of 30 seconds
  • Payload size limit of 1MB

Request

Amplify GraphQL directive

List of fields

typeName (String)
The name of the parent object type of the field being resolver.
fieldName (String)
The name of the field being resolved.
arguments (Map)
A map containing the arguments passed to the field being resolved.
identity (Object)
A map containing identity information for the request. Contains a nested key 'claims' that will contains the JWT claims if they exist.
source (Map)
A map that contains the resolution of the parent field. When resolving a nested field in a query, the source contains parent value at runtime. For example when resolving Post.comments, the source will be the Post object.
request (String)
The AppSync request object. Contains header information.
next (String)
When using pipeline resolvers, this contains the object returned by the previous function. You can return the previous value for auditing use cases.
Amplify GraphQL directive
{
  "typeName": "Merchant",
  "fieldName": "locations",
  "arguments": {
    "page": 2,
    "size": 1,
    "name": "value"
  },
  "identity": {
    "claims": {
      "sub": "07920713-4526-4642-9c88-2953512de441",
      "iss": "https://cognito-idp.us-east-1.amazonaws.com/us-east-1_POOL_ID",
      "aud": "58rc9bf5kkti90ctmvioppukm9",
      "event_id": "7f4c9383-abf6-48b7-b821-91643968b755",
      "token_use": "id",
      "auth_time": 1615366261,
      "name": "Michael Brewer",
      "exp": 1615369861,
      "iat": 1615366261
    },
    "defaultAuthStrategy": "ALLOW",
    "groups": null,
    "issuer": "https://cognito-idp.us-east-1.amazonaws.com/us-east-1_POOL_ID",
    "sourceIp": [
      "11.215.2.22"
    ],
    "sub": "07920713-4526-4642-9c88-2953512de441",
    "username": "mike"
  },
  "source": {
    "name": "Value",
    "nested": {
      "name": "value",
      "list": []
    }
  },
  "request": {
    "headers": {
      "x-forwarded-for": "11.215.2.22, 64.44.173.11",
      "cloudfront-viewer-country": "US",
      "cloudfront-is-tablet-viewer": "false",
      "via": "2.0 SOMETHING.cloudfront.net (CloudFront)",
      "cloudfront-forwarded-proto": "https",
      "origin": "https://console.aws.amazon.com",
      "content-length": "156",
      "accept-language": "en-US,en;q=0.9",
      "host": "SOMETHING.appsync-api.us-east-1.amazonaws.com",
      "x-forwarded-proto": "https",
      "sec-gpc": "1",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) etc.",
      "accept": "*/*",
      "cloudfront-is-mobile-viewer": "false",
      "cloudfront-is-smarttv-viewer": "false",
      "accept-encoding": "gzip, deflate, br",
      "referer": "https://console.aws.amazon.com/",
      "content-type": "application/json",
      "sec-fetch-mode": "cors",
      "x-amz-cf-id": "Fo5VIuvP6V6anIEt62WzFDCK45mzM4yEdpt5BYxOl9OFqafd-WR0cA==",
      "x-amzn-trace-id": "Root=1-60488877-0b0c4e6727ab2a1c545babd0",
      "authorization": "AUTH-HEADER",
      "sec-fetch-dest": "empty",
      "x-amz-user-agent": "AWS-Console-AppSync/",
      "cloudfront-is-desktop-viewer": "true",
      "sec-fetch-site": "cross-site",
      "x-forwarded-port": "443"
    }
  },
  "prev": {
    "result": {}
  }
}

Direct Lambda Resolver

List of fields

info.parentTypeName (String)
The name of the parent object type of the field being resolver.
info.fieldName (String)
The name of the field being resolved.
arguments (Map)
A map containing the arguments passed to the field being resolved.
identity (Object)
A map containing identity information for the request. Contains a nested key 'claims' that will contains the JWT claims if they exist.
source (Map)
A map that contains the resolution of the parent field. When resolving a nested field in a query, the source contains parent value at runtime. For example when resolving Post.comments, the source will be the Post object.
request (String)
The AppSync request object. Contains header information.
next (String)
When using pipeline resolvers, this contains the object returned by the previous function. You can return the previous value for auditing use cases.
AppSync direct resolver
{
  "arguments": {
    "id": "my identifier"
  },
  "identity": {
    "claims": {
      "sub": "192879fc-a240-4bf1-ab5a-d6a00f3063f9",
      "email_verified": true,
      "iss": "https://cognito-idp.us-west-2.amazonaws.com/us-west-xxxxxxxxxxx",
      "phone_number_verified": false,
      "cognito:username": "jdoe",
      "aud": "7471s60os7h0uu77i1tk27sp9n",
      "event_id": "bc334ed8-a938-4474-b644-9547e304e606",
      "token_use": "id",
      "auth_time": 1599154213,
      "phone_number": "+19999999999",
      "exp": 1599157813,
      "iat": 1599154213,
      "email": "jdoe@email.com"
    },
    "defaultAuthStrategy": "ALLOW",
    "groups": null,
    "issuer": "https://cognito-idp.us-west-2.amazonaws.com/us-west-xxxxxxxxxxx",
    "sourceIp": [
      "1.1.1.1"
    ],
    "sub": "192879fc-a240-4bf1-ab5a-d6a00f3063f9",
    "username": "jdoe"
  },
  "source": null,
  "request": {
    "headers": {
      "x-forwarded-for": "1.1.1.1, 2.2.2.2",
      "cloudfront-viewer-country": "US",
      "cloudfront-is-tablet-viewer": "false",
      "via": "2.0 xxxxxxxxxxxxxxxx.cloudfront.net (CloudFront)",
      "cloudfront-forwarded-proto": "https",
      "origin": "https://us-west-1.console.aws.amazon.com",
      "content-length": "217",
      "accept-language": "en-US,en;q=0.9",
      "host": "xxxxxxxxxxxxxxxx.appsync-api.us-west-1.amazonaws.com",
      "x-forwarded-proto": "https",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36",
      "accept": "*/*",
      "cloudfront-is-mobile-viewer": "false",
      "cloudfront-is-smarttv-viewer": "false",
      "accept-encoding": "gzip, deflate, br",
      "referer": "https://us-west-1.console.aws.amazon.com/appsync/home?region=us-west-1",
      "content-type": "application/json",
      "sec-fetch-mode": "cors",
      "x-amz-cf-id": "3aykhqlUwQeANU-HGY7E_guV5EkNeMMtwyOgiA==",
      "x-amzn-trace-id": "Root=1-5f512f51-fac632066c5e848ae714",
      "authorization": "eyJraWQiOiJScWFCSlJqYVJlM0hrSnBTUFpIcVRXazNOW...",
      "sec-fetch-dest": "empty",
      "x-amz-user-agent": "AWS-Console-AppSync/",
      "cloudfront-is-desktop-viewer": "true",
      "sec-fetch-site": "cross-site",
      "x-forwarded-port": "443"
    }
  },
  "prev": null,
  "info": {
    "selectionSetList": [
      "id",
      "field1",
      "field2"
    ],
    "selectionSetGraphQL": "{\n  id\n  field1\n  field2\n}",
    "parentTypeName": "Mutation",
    "fieldName": "createSomething",
    "variables": {}
  },
  "stash": {}
}

Response

Response is based on the expected GraphQL response.

Resources

Typed handlers by language

Lambda handlers by language

Code Examples

AppSync resolver using AWS Lambda Powertools
from aws_lambda_powertools import Logger, Tracer

from aws_lambda_powertools.logging import correlation_paths
from aws_lambda_powertools.event_handler import AppSyncResolver
from aws_lambda_powertools.utilities.data_classes.appsync import scalar_types_utils

tracer = Tracer(service="sample_resolver")
logger = Logger(service="sample_resolver")
app = AppSyncResolver()

# Note that `creation_time` isn't available in the schema
# This utility also takes into account what info you make available at API level vs what's stored
TODOS = [
    {
        "id": scalar_types_utils.make_id(), # type ID or String
        "title": "First task",
        "description": "String",
        "done": False,
        "creation_time": scalar_types_utils.aws_datetime(),  # type AWSDateTime
    },
    {
        "id": scalar_types_utils.make_id(),
        "title": "Second task",
        "description": "String",
        "done": True,
        "creation_time": scalar_types_utils.aws_datetime(),
    },
]


@app.resolver(type_name="Query", field_name="getTodo")
def get_todo(id: str = ""):
    logger.info(f"Fetching Todo {id}")
    todo = [todo for todo in TODOS if todo["id"] == id]

    return todo


@app.resolver(type_name="Query", field_name="listTodos")
def list_todos():
    return TODOS


@logger.inject_lambda_context(correlation_id_path=correlation_paths.APPSYNC_RESOLVER)
@tracer.capture_lambda_handler
def lambda_handler(event, context):
    return app.resolve(event, context)

Documentation


Last update: 2022-09-13