/*!

* Copyright 2019 Google Inc. All Rights Reserved.

*

* 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 {grpc} from 'google-gax';

/*!

* retryable grpc.status codes

*/

export const RETRY_CODES: grpc.status[] = [

grpc.status.DEADLINE_EXCEEDED,

grpc.status.RESOURCE_EXHAUSTED,

grpc.status.ABORTED,

grpc.status.INTERNAL,

grpc.status.UNAVAILABLE,

];

/**

* Used to track pull requests and determine if additional requests should be

* made, etc.

*

* @class

* @private

*/

export class PullRetry {

private failures = 0;

/**

* Generates a timeout that can be used for applying a backoff based on the

* current number of failed requests.

*

* @see {@link https://cloud.google.com/iot/docs/how-tos/exponential-backoff}

* @private

* @returns {number}

*/

createTimeout(): number {

if (this.failures === 0) {

return 0;

}

return Math.pow(2, this.failures) * 1000 + Math.floor(Math.random() * 1000);

}

/**

* Determines if a request grpc.status should be retried.

*

* Deadlines behave kind of unexpectedly on streams, rather than using it as

* an indicator of when to give up trying to connect, it actually dictates

* how long the stream should stay open. Because of this, it is virtually

* impossible to determine whether or not a deadline error is the result of

* the server closing the stream or if we timed out waiting for a connection.

*

* @private

* @param {object} grpc.status The request grpc.status.

* @returns {boolean}

*/

retry(err: grpc.StatusObject): boolean {

if (

err.code === grpc.status.OK ||

err.code === grpc.status.DEADLINE_EXCEEDED

) {

this.failures = 0;

} else {

this.failures += 1;

}

if (

err.code === grpc.status.UNAVAILABLE &&

err.details &&

err.details.match(/Server shutdownNow invoked/)

) {

return true;

}

return RETRY_CODES.includes(err.code);

}

}