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api-request.ts
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1017 lines (878 loc) · 31.1 KB
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/*!
* @license
* Copyright 2017 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import { FirebaseApp } from '../app/firebase-app';
import { AppErrorCodes, FirebaseAppError } from './error';
import * as validator from './validator';
import http = require('http');
import https = require('https');
import url = require('url');
import { EventEmitter } from 'events';
import { Readable } from 'stream';
import * as zlibmod from 'zlib';
/** Http method type definition. */
export type HttpMethod = 'GET' | 'POST' | 'PUT' | 'DELETE' | 'PATCH' | 'HEAD';
/** API callback function type definition. */
export type ApiCallbackFunction = (data: object) => void;
/**
* Configuration for constructing a new HTTP request.
*/
export interface HttpRequestConfig {
method: HttpMethod;
/** Target URL of the request. Should be a well-formed URL including protocol, hostname, port and path. */
url: string;
headers?: {[key: string]: string};
data?: string | object | Buffer | null;
/** Connect and read timeout (in milliseconds) for the outgoing request. */
timeout?: number;
httpAgent?: http.Agent;
}
/**
* Represents an HTTP response received from a remote server.
*/
export interface HttpResponse {
readonly status: number;
readonly headers: any;
/** Response data as a raw string. */
readonly text?: string;
/** Response data as a parsed JSON object. */
readonly data?: any;
/** For multipart responses, the payloads of individual parts. */
readonly multipart?: Buffer[];
/**
* Indicates if the response content is JSON-formatted or not. If true, data field can be used
* to retrieve the content as a parsed JSON object.
*/
isJson(): boolean;
}
interface LowLevelResponse {
status: number;
headers: http.IncomingHttpHeaders;
request: http.ClientRequest | null;
data?: string;
multipart?: Buffer[];
config: HttpRequestConfig;
}
interface LowLevelError extends Error {
config: HttpRequestConfig;
code?: string;
request?: http.ClientRequest;
response?: LowLevelResponse;
}
class DefaultHttpResponse implements HttpResponse {
public readonly status: number;
public readonly headers: any;
public readonly text?: string;
private readonly parsedData: any;
private readonly parseError: Error;
private readonly request: string;
/**
* Constructs a new HttpResponse from the given LowLevelResponse.
*/
constructor(resp: LowLevelResponse) {
this.status = resp.status;
this.headers = resp.headers;
this.text = resp.data;
try {
if (!resp.data) {
throw new FirebaseAppError(AppErrorCodes.INTERNAL_ERROR, 'HTTP response missing data.');
}
this.parsedData = JSON.parse(resp.data);
} catch (err) {
this.parsedData = undefined;
this.parseError = err;
}
this.request = `${resp.config.method} ${resp.config.url}`;
}
get data(): any {
if (this.isJson()) {
return this.parsedData;
}
throw new FirebaseAppError(
AppErrorCodes.UNABLE_TO_PARSE_RESPONSE,
`Error while parsing response data: "${ this.parseError.toString() }". Raw server ` +
`response: "${ this.text }". Status code: "${ this.status }". Outgoing ` +
`request: "${ this.request }."`,
);
}
public isJson(): boolean {
return typeof this.parsedData !== 'undefined';
}
}
/**
* Represents a multipart HTTP response. Parts that constitute the response body can be accessed
* via the multipart getter. Getters for text and data throw errors.
*/
class MultipartHttpResponse implements HttpResponse {
public readonly status: number;
public readonly headers: any;
public readonly multipart?: Buffer[];
constructor(resp: LowLevelResponse) {
this.status = resp.status;
this.headers = resp.headers;
this.multipart = resp.multipart;
}
get text(): string {
throw new FirebaseAppError(
AppErrorCodes.UNABLE_TO_PARSE_RESPONSE,
'Unable to parse multipart payload as text',
);
}
get data(): any {
throw new FirebaseAppError(
AppErrorCodes.UNABLE_TO_PARSE_RESPONSE,
'Unable to parse multipart payload as JSON',
);
}
public isJson(): boolean {
return false;
}
}
export class HttpError extends Error {
constructor(public readonly response: HttpResponse) {
super(`Server responded with status ${response.status}.`);
// Set the prototype so that instanceof checks will work correctly.
// See: https://github.com/Microsoft/TypeScript/issues/13965
Object.setPrototypeOf(this, HttpError.prototype);
}
}
/**
* Specifies how failing HTTP requests should be retried.
*/
export interface RetryConfig {
/** Maximum number of times to retry a given request. */
maxRetries: number;
/** HTTP status codes that should be retried. */
statusCodes?: number[];
/** Low-level I/O error codes that should be retried. */
ioErrorCodes?: string[];
/**
* The multiplier for exponential back off. The retry delay is calculated in seconds using the formula
* `(2^n) * backOffFactor`, where n is the number of retries performed so far. When the backOffFactor is set
* to 0, retries are not delayed. When the backOffFactor is 1, retry duration is doubled each iteration.
*/
backOffFactor?: number;
/** Maximum duration to wait before initiating a retry. */
maxDelayInMillis: number;
}
/**
* Default retry configuration for HTTP requests. Retries up to 4 times on connection reset and timeout errors
* as well as HTTP 503 errors. Exposed as a function to ensure that every HttpClient gets its own RetryConfig
* instance.
*/
export function defaultRetryConfig(): RetryConfig {
return {
maxRetries: 4,
statusCodes: [503],
ioErrorCodes: ['ECONNRESET', 'ETIMEDOUT'],
backOffFactor: 0.5,
maxDelayInMillis: 60 * 1000,
};
}
/**
* Ensures that the given RetryConfig object is valid.
*
* @param retry - The configuration to be validated.
*/
function validateRetryConfig(retry: RetryConfig): void {
if (!validator.isNumber(retry.maxRetries) || retry.maxRetries < 0) {
throw new FirebaseAppError(
AppErrorCodes.INVALID_ARGUMENT, 'maxRetries must be a non-negative integer');
}
if (typeof retry.backOffFactor !== 'undefined') {
if (!validator.isNumber(retry.backOffFactor) || retry.backOffFactor < 0) {
throw new FirebaseAppError(
AppErrorCodes.INVALID_ARGUMENT, 'backOffFactor must be a non-negative number');
}
}
if (!validator.isNumber(retry.maxDelayInMillis) || retry.maxDelayInMillis < 0) {
throw new FirebaseAppError(
AppErrorCodes.INVALID_ARGUMENT, 'maxDelayInMillis must be a non-negative integer');
}
if (typeof retry.statusCodes !== 'undefined' && !validator.isArray(retry.statusCodes)) {
throw new FirebaseAppError(AppErrorCodes.INVALID_ARGUMENT, 'statusCodes must be an array');
}
if (typeof retry.ioErrorCodes !== 'undefined' && !validator.isArray(retry.ioErrorCodes)) {
throw new FirebaseAppError(AppErrorCodes.INVALID_ARGUMENT, 'ioErrorCodes must be an array');
}
}
export class HttpClient {
constructor(private readonly retry: RetryConfig | null = defaultRetryConfig()) {
if (this.retry) {
validateRetryConfig(this.retry);
}
}
/**
* Sends an HTTP request to a remote server. If the server responds with a successful response (2xx), the returned
* promise resolves with an HttpResponse. If the server responds with an error (3xx, 4xx, 5xx), the promise rejects
* with an HttpError. In case of all other errors, the promise rejects with a FirebaseAppError. If a request fails
* due to a low-level network error, transparently retries the request once before rejecting the promise.
*
* If the request data is specified as an object, it will be serialized into a JSON string. The application/json
* content-type header will also be automatically set in this case. For all other payload types, the content-type
* header should be explicitly set by the caller. To send a JSON leaf value (e.g. "foo", 5), parse it into JSON,
* and pass as a string or a Buffer along with the appropriate content-type header.
*
* @param config - HTTP request to be sent.
* @returns A promise that resolves with the response details.
*/
public send(config: HttpRequestConfig): Promise<HttpResponse> {
return this.sendWithRetry(config);
}
/**
* Sends an HTTP request. In the event of an error, retries the HTTP request according to the
* RetryConfig set on the HttpClient.
*
* @param config - HTTP request to be sent.
* @param retryAttempts - Number of retries performed up to now.
* @returns A promise that resolves with the response details.
*/
private sendWithRetry(config: HttpRequestConfig, retryAttempts = 0): Promise<HttpResponse> {
return AsyncHttpCall.invoke(config)
.then((resp) => {
return this.createHttpResponse(resp);
})
.catch((err: LowLevelError) => {
const [delayMillis, canRetry] = this.getRetryDelayMillis(retryAttempts, err);
if (canRetry && this.retry && delayMillis <= this.retry.maxDelayInMillis) {
return this.waitForRetry(delayMillis).then(() => {
return this.sendWithRetry(config, retryAttempts + 1);
});
}
if (err.response) {
throw new HttpError(this.createHttpResponse(err.response));
}
if (err.code === 'ETIMEDOUT') {
throw new FirebaseAppError(
AppErrorCodes.NETWORK_TIMEOUT,
`Error while making request: ${err.message}.`);
}
throw new FirebaseAppError(
AppErrorCodes.NETWORK_ERROR,
`Error while making request: ${err.message}. Error code: ${err.code}`);
});
}
private createHttpResponse(resp: LowLevelResponse): HttpResponse {
if (resp.multipart) {
return new MultipartHttpResponse(resp);
}
return new DefaultHttpResponse(resp);
}
private waitForRetry(delayMillis: number): Promise<void> {
if (delayMillis > 0) {
return new Promise((resolve) => {
setTimeout(resolve, delayMillis);
});
}
return Promise.resolve();
}
/**
* Checks if a failed request is eligible for a retry, and if so returns the duration to wait before initiating
* the retry.
*
* @param retryAttempts - Number of retries completed up to now.
* @param err - The last encountered error.
* @returns A 2-tuple where the 1st element is the duration to wait before another retry, and the
* 2nd element is a boolean indicating whether the request is eligible for a retry or not.
*/
private getRetryDelayMillis(retryAttempts: number, err: LowLevelError): [number, boolean] {
if (!this.isRetryEligible(retryAttempts, err)) {
return [0, false];
}
const response = err.response;
if (response && response.headers['retry-after']) {
const delayMillis = this.parseRetryAfterIntoMillis(response.headers['retry-after']);
if (delayMillis > 0) {
return [delayMillis, true];
}
}
return [this.backOffDelayMillis(retryAttempts), true];
}
private isRetryEligible(retryAttempts: number, err: LowLevelError): boolean {
if (!this.retry) {
return false;
}
if (retryAttempts >= this.retry.maxRetries) {
return false;
}
if (err.response) {
const statusCodes = this.retry.statusCodes || [];
return statusCodes.indexOf(err.response.status) !== -1;
}
if (err.code) {
const retryCodes = this.retry.ioErrorCodes || [];
return retryCodes.indexOf(err.code) !== -1;
}
return false;
}
/**
* Parses the Retry-After HTTP header as a milliseconds value. Return value is negative if the Retry-After header
* contains an expired timestamp or otherwise malformed.
*/
private parseRetryAfterIntoMillis(retryAfter: string): number {
const delaySeconds: number = parseInt(retryAfter, 10);
if (!isNaN(delaySeconds)) {
return delaySeconds * 1000;
}
const date = new Date(retryAfter);
if (!isNaN(date.getTime())) {
return date.getTime() - Date.now();
}
return -1;
}
private backOffDelayMillis(retryAttempts: number): number {
if (retryAttempts === 0) {
return 0;
}
if (!this.retry) {
throw new FirebaseAppError(AppErrorCodes.INTERNAL_ERROR, 'Expected this.retry to exist.');
}
const backOffFactor = this.retry.backOffFactor || 0;
const delayInSeconds = (2 ** retryAttempts) * backOffFactor;
return Math.min(delayInSeconds * 1000, this.retry.maxDelayInMillis);
}
}
/**
* Parses a full HTTP response message containing both a header and a body.
*
* @param response - The HTTP response to be parsed.
* @param config - The request configuration that resulted in the HTTP response.
* @returns An object containing the parsed HTTP status, headers and the body.
*/
export function parseHttpResponse(
response: string | Buffer, config: HttpRequestConfig): HttpResponse {
const responseText: string = validator.isBuffer(response) ?
response.toString('utf-8') : response as string;
const endOfHeaderPos: number = responseText.indexOf('\r\n\r\n');
const headerLines: string[] = responseText.substring(0, endOfHeaderPos).split('\r\n');
const statusLine: string = headerLines[0];
const status: string = statusLine.trim().split(/\s/)[1];
const headers: {[key: string]: string} = {};
headerLines.slice(1).forEach((line) => {
const colonPos = line.indexOf(':');
const name = line.substring(0, colonPos).trim().toLowerCase();
const value = line.substring(colonPos + 1).trim();
headers[name] = value;
});
let data = responseText.substring(endOfHeaderPos + 4);
if (data.endsWith('\n')) {
data = data.slice(0, -1);
}
if (data.endsWith('\r')) {
data = data.slice(0, -1);
}
const lowLevelResponse: LowLevelResponse = {
status: parseInt(status, 10),
headers,
data,
config,
request: null,
};
if (!validator.isNumber(lowLevelResponse.status)) {
throw new FirebaseAppError(AppErrorCodes.INTERNAL_ERROR, 'Malformed HTTP status line.');
}
return new DefaultHttpResponse(lowLevelResponse);
}
/**
* A helper class for sending HTTP requests over the wire. This is a wrapper around the standard
* http and https packages of Node.js, providing content processing, timeouts and error handling.
* It also wraps the callback API of the Node.js standard library in a more flexible Promise API.
*/
class AsyncHttpCall {
private readonly config: HttpRequestConfigImpl;
private readonly options: https.RequestOptions;
private readonly entity: Buffer | undefined;
private readonly promise: Promise<LowLevelResponse>;
private resolve: (_: any) => void;
private reject: (_: any) => void;
/**
* Sends an HTTP request based on the provided configuration.
*/
public static invoke(config: HttpRequestConfig): Promise<LowLevelResponse> {
return new AsyncHttpCall(config).promise;
}
private constructor(config: HttpRequestConfig) {
try {
this.config = new HttpRequestConfigImpl(config);
this.options = this.config.buildRequestOptions();
this.entity = this.config.buildEntity(this.options.headers!);
this.promise = new Promise((resolve, reject) => {
this.resolve = resolve;
this.reject = reject;
this.execute();
});
} catch (err) {
this.promise = Promise.reject(this.enhanceError(err, null));
}
}
private execute(): void {
const transport: any = this.options.protocol === 'https:' ? https : http;
const req: http.ClientRequest = transport.request(this.options, (res: http.IncomingMessage) => {
this.handleResponse(res, req);
});
// Handle errors
req.on('error', (err) => {
if (req.aborted) {
return;
}
this.enhanceAndReject(err, null, req);
});
const timeout: number | undefined = this.config.timeout;
const timeoutCallback: () => void = () => {
req.abort();
this.rejectWithError(`timeout of ${timeout}ms exceeded`, 'ETIMEDOUT', req);
};
if (timeout) {
// Listen to timeouts and throw an error.
req.setTimeout(timeout, timeoutCallback);
req.on('socket', (socket) => {
socket.setMaxListeners(socket.getMaxListeners() + 1);
socket.setTimeout(timeout, timeoutCallback);
socket.on('end', () => {
socket.setTimeout(0);
socket.setMaxListeners(Math.max(socket.getMaxListeners() - 1, 0));
});
});
}
// Send the request
req.end(this.entity);
}
private handleResponse(res: http.IncomingMessage, req: http.ClientRequest): void {
if (req.aborted) {
return;
}
if (!res.statusCode) {
throw new FirebaseAppError(
AppErrorCodes.INTERNAL_ERROR,
'Expected a statusCode on the response from a ClientRequest');
}
const response: LowLevelResponse = {
status: res.statusCode,
headers: res.headers,
request: req,
data: undefined,
config: this.config,
};
const boundary = this.getMultipartBoundary(res.headers);
const respStream: Readable = this.uncompressResponse(res);
if (boundary) {
this.handleMultipartResponse(response, respStream, boundary);
} else {
this.handleRegularResponse(response, respStream);
}
}
/**
* Extracts multipart boundary from the HTTP header. The content-type header of a multipart
* response has the form 'multipart/subtype; boundary=string'.
*
* If the content-type header does not exist, or does not start with
* 'multipart/', then null will be returned.
*/
private getMultipartBoundary(headers: http.IncomingHttpHeaders): string | null {
const contentType = headers['content-type'];
if (!contentType || !contentType.startsWith('multipart/')) {
return null;
}
const segments: string[] = contentType.split(';');
const emptyObject: {[key: string]: string} = {};
const headerParams = segments.slice(1)
.map((segment) => segment.trim().split('='))
.reduce((curr, params) => {
// Parse key=value pairs in the content-type header into properties of an object.
if (params.length === 2) {
const keyValuePair: {[key: string]: string} = {};
keyValuePair[params[0]] = params[1];
return Object.assign(curr, keyValuePair);
}
return curr;
}, emptyObject);
return headerParams.boundary;
}
private uncompressResponse(res: http.IncomingMessage): Readable {
// Uncompress the response body transparently if required.
let respStream: Readable = res;
const encodings = ['gzip', 'compress', 'deflate'];
if (res.headers['content-encoding'] && encodings.indexOf(res.headers['content-encoding']) !== -1) {
// Add the unzipper to the body stream processing pipeline.
const zlib: typeof zlibmod = require('zlib'); // eslint-disable-line @typescript-eslint/no-var-requires
respStream = respStream.pipe(zlib.createUnzip());
// Remove the content-encoding in order to not confuse downstream operations.
delete res.headers['content-encoding'];
}
return respStream;
}
private handleMultipartResponse(
response: LowLevelResponse, respStream: Readable, boundary: string): void {
const busboy = require('@fastify/busboy'); // eslint-disable-line @typescript-eslint/no-var-requires
const multipartParser = new busboy.Dicer({ boundary });
const responseBuffer: Buffer[] = [];
multipartParser.on('part', (part: any) => {
const tempBuffers: Buffer[] = [];
part.on('data', (partData: Buffer) => {
tempBuffers.push(partData);
});
part.on('end', () => {
responseBuffer.push(Buffer.concat(tempBuffers));
});
});
multipartParser.on('finish', () => {
response.data = undefined;
response.multipart = responseBuffer;
this.finalizeResponse(response);
});
respStream.pipe(multipartParser);
}
private handleRegularResponse(response: LowLevelResponse, respStream: Readable): void {
const responseBuffer: Buffer[] = [];
respStream.on('data', (chunk: Buffer) => {
responseBuffer.push(chunk);
});
respStream.on('error', (err) => {
const req: http.ClientRequest | null = response.request;
if (req && req.aborted) {
return;
}
this.enhanceAndReject(err, null, req);
});
respStream.on('end', () => {
response.data = Buffer.concat(responseBuffer).toString();
this.finalizeResponse(response);
});
}
/**
* Finalizes the current HTTP call in-flight by either resolving or rejecting the associated
* promise. In the event of an error, adds additional useful information to the returned error.
*/
private finalizeResponse(response: LowLevelResponse): void {
if (response.status >= 200 && response.status < 300) {
this.resolve(response);
} else {
this.rejectWithError(
'Request failed with status code ' + response.status,
null,
response.request,
response,
);
}
}
/**
* Creates a new error from the given message, and enhances it with other information available.
* Then the promise associated with this HTTP call is rejected with the resulting error.
*/
private rejectWithError(
message: string,
code?: string | null,
request?: http.ClientRequest | null,
response?: LowLevelResponse): void {
const error = new Error(message);
this.enhanceAndReject(error, code, request, response);
}
private enhanceAndReject(
error: any,
code?: string | null,
request?: http.ClientRequest | null,
response?: LowLevelResponse): void {
this.reject(this.enhanceError(error, code, request, response));
}
/**
* Enhances the given error by adding more information to it. Specifically, the HttpRequestConfig,
* the underlying request and response will be attached to the error.
*/
private enhanceError(
error: any,
code?: string | null,
request?: http.ClientRequest | null,
response?: LowLevelResponse): LowLevelError {
error.config = this.config;
if (code) {
error.code = code;
}
error.request = request;
error.response = response;
return error;
}
}
/**
* An adapter class for extracting options and entity data from an HttpRequestConfig.
*/
class HttpRequestConfigImpl implements HttpRequestConfig {
constructor(private readonly config: HttpRequestConfig) {
}
get method(): HttpMethod {
return this.config.method;
}
get url(): string {
return this.config.url;
}
get headers(): {[key: string]: string} | undefined {
return this.config.headers;
}
get data(): string | object | Buffer | undefined | null {
return this.config.data;
}
get timeout(): number | undefined {
return this.config.timeout;
}
get httpAgent(): http.Agent | undefined {
return this.config.httpAgent;
}
public buildRequestOptions(): https.RequestOptions {
const parsed = this.buildUrl();
const protocol = parsed.protocol;
let port: string | null = parsed.port;
if (!port) {
const isHttps = protocol === 'https:';
port = isHttps ? '443' : '80';
}
return {
protocol,
hostname: parsed.hostname,
port,
path: parsed.path,
method: this.method,
agent: this.httpAgent,
headers: Object.assign({}, this.headers),
};
}
public buildEntity(headers: http.OutgoingHttpHeaders): Buffer | undefined {
let data: Buffer | undefined;
if (!this.hasEntity() || !this.isEntityEnclosingRequest()) {
return data;
}
if (validator.isBuffer(this.data)) {
data = this.data as Buffer;
} else if (validator.isObject(this.data)) {
data = Buffer.from(JSON.stringify(this.data), 'utf-8');
if (typeof headers['content-type'] === 'undefined') {
headers['content-type'] = 'application/json;charset=utf-8';
}
} else if (validator.isString(this.data)) {
data = Buffer.from(this.data as string, 'utf-8');
} else {
throw new Error('Request data must be a string, a Buffer or a json serializable object');
}
// Add Content-Length header if data exists.
headers['Content-Length'] = data.length.toString();
return data;
}
private buildUrl(): url.UrlWithStringQuery {
const fullUrl: string = this.urlWithProtocol();
if (!this.hasEntity() || this.isEntityEnclosingRequest()) {
return url.parse(fullUrl);
}
if (!validator.isObject(this.data)) {
throw new Error(`${this.method} requests cannot have a body`);
}
// Parse URL and append data to query string.
const parsedUrl = new url.URL(fullUrl);
const dataObj = this.data as {[key: string]: string};
for (const key in dataObj) {
if (Object.prototype.hasOwnProperty.call(dataObj, key)) {
parsedUrl.searchParams.append(key, dataObj[key]);
}
}
return url.parse(parsedUrl.toString());
}
private urlWithProtocol(): string {
const fullUrl: string = this.url;
if (fullUrl.startsWith('http://') || fullUrl.startsWith('https://')) {
return fullUrl;
}
return `https://${fullUrl}`;
}
private hasEntity(): boolean {
return !!this.data;
}
private isEntityEnclosingRequest(): boolean {
// GET and HEAD requests do not support entity (body) in request.
return this.method !== 'GET' && this.method !== 'HEAD';
}
}
export class AuthorizedHttpClient extends HttpClient {
constructor(private readonly app: FirebaseApp) {
super();
}
public send(request: HttpRequestConfig): Promise<HttpResponse> {
return this.getToken().then((token) => {
const requestCopy = Object.assign({}, request);
requestCopy.headers = Object.assign({}, request.headers);
const authHeader = 'Authorization';
requestCopy.headers[authHeader] = `Bearer ${token}`;
if (!requestCopy.httpAgent && this.app.options.httpAgent) {
requestCopy.httpAgent = this.app.options.httpAgent;
}
return super.send(requestCopy);
});
}
protected getToken(): Promise<string> {
return this.app.INTERNAL.getToken()
.then((accessTokenObj) => {
return accessTokenObj.accessToken;
});
}
}
/**
* Class that defines all the settings for the backend API endpoint.
*
* @param endpoint - The Firebase Auth backend endpoint.
* @param httpMethod - The http method for that endpoint.
* @constructor
*/
export class ApiSettings {
private requestValidator: ApiCallbackFunction;
private responseValidator: ApiCallbackFunction;
constructor(private endpoint: string, private httpMethod: HttpMethod = 'POST') {
this.setRequestValidator(null)
.setResponseValidator(null);
}
/** @returns The backend API endpoint. */
public getEndpoint(): string {
return this.endpoint;
}
/** @returns The request HTTP method. */
public getHttpMethod(): HttpMethod {
return this.httpMethod;
}
/**
* @param requestValidator - The request validator.
* @returns The current API settings instance.
*/
public setRequestValidator(requestValidator: ApiCallbackFunction | null): ApiSettings {
const nullFunction: ApiCallbackFunction = () => undefined;
this.requestValidator = requestValidator || nullFunction;
return this;
}
/** @returns The request validator. */
public getRequestValidator(): ApiCallbackFunction {
return this.requestValidator;
}
/**
* @param responseValidator - The response validator.
* @returns The current API settings instance.
*/
public setResponseValidator(responseValidator: ApiCallbackFunction | null): ApiSettings {
const nullFunction: ApiCallbackFunction = () => undefined;
this.responseValidator = responseValidator || nullFunction;
return this;
}
/** @returns The response validator. */
public getResponseValidator(): ApiCallbackFunction {
return this.responseValidator;
}
}
/**
* Class used for polling an endpoint with exponential backoff.
*
* Example usage:
* ```
* const poller = new ExponentialBackoffPoller();
* poller
* .poll(() => {
* return myRequestToPoll()
* .then((responseData: any) => {
* if (!isValid(responseData)) {
* // Continue polling.
* return null;
* }
*
* // Polling complete. Resolve promise with final response data.
* return responseData;
* });
* })
* .then((responseData: any) => {
* console.log(`Final response: ${responseData}`);
* });
* ```
*/
export class ExponentialBackoffPoller<T> extends EventEmitter {
private numTries = 0;
private completed = false;
private masterTimer: NodeJS.Timer;
private repollTimer: NodeJS.Timer;
private pollCallback?: () => Promise<T>;
private resolve: (result: T) => void;
private reject: (err: object) => void;
constructor(
private readonly initialPollingDelayMillis: number = 1000,
private readonly maxPollingDelayMillis: number = 10000,
private readonly masterTimeoutMillis: number = 60000) {
super();
}
/**
* Poll the provided callback with exponential backoff.
*
* @param callback - The callback to be called for each poll. If the
* callback resolves to a falsey value, polling will continue. Otherwise, the truthy
* resolution will be used to resolve the promise returned by this method.
* @returns A Promise which resolves to the truthy value returned by the provided
* callback when polling is complete.
*/
public poll(callback: () => Promise<T>): Promise<T> {
if (this.pollCallback) {
throw new Error('poll() can only be called once per instance of ExponentialBackoffPoller');
}
this.pollCallback = callback;
this.on('poll', this.repoll);
this.masterTimer = setTimeout(() => {
if (this.completed) {
return;
}
this.markCompleted();
this.reject(new Error('ExponentialBackoffPoller deadline exceeded - Master timeout reached'));
}, this.masterTimeoutMillis);
return new Promise<T>((resolve, reject) => {
this.resolve = resolve;
this.reject = reject;
this.repoll();
});
}
private repoll(): void {
this.pollCallback!()
.then((result) => {
if (this.completed) {
return;
}
if (!result) {
this.repollTimer =
setTimeout(() => this.emit('poll'), this.getPollingDelayMillis());
this.numTries++;
return;
}
this.markCompleted();
this.resolve(result);
})
.catch((err) => {
if (this.completed) {
return;
}
this.markCompleted();
this.reject(err);
});