🚒 Add a simple interceptor to all of your Amplify API mutations and queries!

graphql-firehose-transformer

Installation

npm install --save graphql-firehose-transformer

How to use

Setup custom transformer

Edit amplify/backend/api/<YOUR_API>/transform.conf.json and append "graphql-firehose-transformer" to the transformers field.

"transformers": [
    "graphql-firehose-transformer"
]

Use @firehose directive

Append @firehose to target types and add the name of the separately deployed function that should be called for every mutation and query to this type as argument.

type Todo @model @firehose(name: "auditlog-${env}") {
  id: ID!
  title: String!
  description: String
}

In this example, the auditlog-${env} lambda will be called before every mutation or query to the Todo type, which is ideal to build an audit logger for example.

If you deployed your function using the 'amplify function' category

The Amplify CLI provides support for maintaining multiple environments out of the box. When you deploy a function via amplify add function, it will automatically add the environment suffix to your Lambda function name. For example if you create a function named auditlog using amplify add function in the dev environment, the deployed function will be named auditlog-dev. The @firehose directive allows you to use ${env} to reference the current Amplify CLI environment.

type Todo @model @firehose(name: "auditlog-${env}") {
  id: ID!
  title: String!
  description: String
}

If you deployed your function without amplify

If you deployed your API without amplify then you must provide the full Lambda function name. If you deployed the same function with the name auditlog then you would have:

type Todo @model @firehose(name: "auditlog") {
  id: ID!
  title: String!
  description: String
}

Calling functions in different regions

By default, you expect the function to be in the same region as the amplify project. If you need to call a function in a different (or static) region, you can provide the region argument.

type Todo @model @firehose(name: "auditlog", region: "us-east-1") {
  id: ID!
  title: String!
  description: String
}

Calling functions in different AWS accounts is not supported via the @firehose directive but is supported by AWS AppSync.

Structure of the function event

When writing lambda functions that are connected via the @firehose directive, you can expect the following structure for the AWS Lambda event object.

| Key | Description | | --------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | typeName | Either Mutation or Query. | | fieldName | The mutation or query type field that was called, e.g. createTodo. | | arguments | A map containing the arguments passed to the field being resolved. | | identity | A map containing identity information for the request. Contains a nested key 'claims' that will contains the JWT claims if they exist. | | source | 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 | The AppSync request object. Contains header information. | | prev | When using pipeline resolvers, this contains the object returned by the previous function. You can return the previous value for auditing use cases. |

Contribute 🦸

Please feel free to create, comment and of course solve some of the issues. To get started you can also go for the easier issues marked with the good first issue label if you like.

Development

• It is important to always make sure the version of the installed graphql dependency matches the graphql version the graphql-transformer-core depends on.

License

The MIT License

Credits

The graphql-firehose-transformer library is maintained and sponsored by Laguna Health, a digital recovery assurance company fusing data, technology, and live behavioral health experts to shorten recovery times and reduce readmissions.

Shout-out to the Swiss web and mobile app developer Florian Gyger who built the initial version of this library.