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113 lines
4.0 KiB
Plaintext
113 lines
4.0 KiB
Plaintext
// Module included in the following assemblies
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//
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// * serverless/functions/serverless-developing-typescript-functions.adoc
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:_content-type: REFERENCE
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[id="serverless-typescript-functions-context-objects_{context}"]
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= TypeScript context objects
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To invoke a function, you provide a `context` object as the first parameter. Accessing properties of the `context` object can provide information about the incoming HTTP request.
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.Example context object
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[source,javascript]
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----
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function handle(context:Context): string
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----
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This information includes the HTTP request method, any query strings or headers sent with the request, the HTTP version, and the request body. Incoming requests that contain a `CloudEvent` attach the incoming instance of the CloudEvent to the context object so that it can be accessed by using `context.cloudevent`.
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[id="serverless-typescript-functions-context-objects-methods_{context}"]
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== Context object methods
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The `context` object has a single method, `cloudEventResponse()`, that accepts a data value and returns a CloudEvent.
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In a Knative system, if a function deployed as a service is invoked by an event broker sending a CloudEvent, the broker examines the response. If the response is a CloudEvent, this event is handled by the broker.
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.Example context object method
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[source,javascript]
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----
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// Expects to receive a CloudEvent with customer data
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export function handle(context: Context, cloudevent?: CloudEvent): CloudEvent {
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// process the customer
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const customer = cloudevent.data;
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const processed = processCustomer(customer);
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return context.cloudEventResponse(customer)
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.source('/customer/process')
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.type('customer.processed')
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.response();
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}
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----
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[id="serverless-typescript-functions-context-types_{context}"]
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== Context types
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The TypeScript type definition files export the following types for use in your functions.
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.Exported type definitions
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[source,javascript]
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----
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// Invokable is the expeted Function signature for user functions
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export interface Invokable {
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(context: Context, cloudevent?: CloudEvent): any
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}
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// Logger can be used for structural logging to the console
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export interface Logger {
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debug: (msg: any) => void,
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info: (msg: any) => void,
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warn: (msg: any) => void,
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error: (msg: any) => void,
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fatal: (msg: any) => void,
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trace: (msg: any) => void,
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}
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// Context represents the function invocation context, and provides
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// access to the event itself as well as raw HTTP objects.
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export interface Context {
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log: Logger;
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req: IncomingMessage;
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query?: Record<string, any>;
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body?: Record<string, any>|string;
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method: string;
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headers: IncomingHttpHeaders;
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httpVersion: string;
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httpVersionMajor: number;
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httpVersionMinor: number;
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cloudevent: CloudEvent;
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cloudEventResponse(data: string|object): CloudEventResponse;
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}
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// CloudEventResponse is a convenience class used to create
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// CloudEvents on function returns
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export interface CloudEventResponse {
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id(id: string): CloudEventResponse;
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source(source: string): CloudEventResponse;
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type(type: string): CloudEventResponse;
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version(version: string): CloudEventResponse;
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response(): CloudEvent;
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}
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----
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[id="serverless-typescript-functions-context-objects-cloudevent-data_{context}"]
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== CloudEvent data
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If the incoming request is a CloudEvent, any data associated with the CloudEvent is extracted from the event and provided as a second parameter. For example, if a CloudEvent is received that contains a JSON string in its data property that is similar to the following:
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[source,json]
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----
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{
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"customerId": "0123456",
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"productId": "6543210"
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}
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----
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When invoked, the second parameter to the function, after the `context` object, will be a JavaScript object that has `customerId` and `productId` properties.
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.Example signature
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[source,javascript]
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----
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function handle(context: Context, cloudevent?: CloudEvent): CloudEvent
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----
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The `cloudevent` parameter in this example is a JavaScript object that contains the `customerId` and `productId` properties.
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