147 lines
4.2 KiB
TypeScript
147 lines
4.2 KiB
TypeScript
/*
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* Copyright 2019 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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import { StatusObject } from './call-interface';
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import { Metadata } from './metadata';
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import { Status } from './constants';
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import { LoadBalancer } from './load-balancer';
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import { SubchannelInterface } from './subchannel-interface';
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export enum PickResultType {
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COMPLETE,
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QUEUE,
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TRANSIENT_FAILURE,
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DROP,
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}
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export interface PickResult {
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pickResultType: PickResultType;
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/**
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* The subchannel to use as the transport for the call. Only meaningful if
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* `pickResultType` is COMPLETE. If null, indicates that the call should be
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* dropped.
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*/
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subchannel: SubchannelInterface | null;
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/**
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* The status object to end the call with. Populated if and only if
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* `pickResultType` is TRANSIENT_FAILURE.
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*/
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status: StatusObject | null;
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onCallStarted: (() => void) | null;
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onCallEnded: ((statusCode: Status) => void) | null;
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}
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export interface CompletePickResult extends PickResult {
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pickResultType: PickResultType.COMPLETE;
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subchannel: SubchannelInterface | null;
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status: null;
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onCallStarted: (() => void) | null;
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onCallEnded: ((statusCode: Status) => void) | null;
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}
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export interface QueuePickResult extends PickResult {
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pickResultType: PickResultType.QUEUE;
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subchannel: null;
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status: null;
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onCallStarted: null;
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onCallEnded: null;
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}
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export interface TransientFailurePickResult extends PickResult {
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pickResultType: PickResultType.TRANSIENT_FAILURE;
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subchannel: null;
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status: StatusObject;
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onCallStarted: null;
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onCallEnded: null;
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}
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export interface DropCallPickResult extends PickResult {
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pickResultType: PickResultType.DROP;
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subchannel: null;
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status: StatusObject;
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onCallStarted: null;
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onCallEnded: null;
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}
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export interface PickArgs {
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metadata: Metadata;
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extraPickInfo: { [key: string]: string };
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}
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/**
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* A proxy object representing the momentary state of a load balancer. Picks
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* subchannels or returns other information based on that state. Should be
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* replaced every time the load balancer changes state.
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*/
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export interface Picker {
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pick(pickArgs: PickArgs): PickResult;
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}
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/**
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* A standard picker representing a load balancer in the TRANSIENT_FAILURE
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* state. Always responds to every pick request with an UNAVAILABLE status.
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*/
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export class UnavailablePicker implements Picker {
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private status: StatusObject;
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constructor(status?: Partial<StatusObject>) {
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this.status = {
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code: Status.UNAVAILABLE,
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details: 'No connection established',
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metadata: new Metadata(),
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...status,
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};
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}
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pick(pickArgs: PickArgs): TransientFailurePickResult {
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return {
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pickResultType: PickResultType.TRANSIENT_FAILURE,
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subchannel: null,
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status: this.status,
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onCallStarted: null,
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onCallEnded: null,
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};
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}
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}
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/**
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* A standard picker representing a load balancer in the IDLE or CONNECTING
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* state. Always responds to every pick request with a QUEUE pick result
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* indicating that the pick should be tried again with the next `Picker`. Also
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* reports back to the load balancer that a connection should be established
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* once any pick is attempted.
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*/
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export class QueuePicker {
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private calledExitIdle = false;
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// Constructed with a load balancer. Calls exitIdle on it the first time pick is called
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constructor(private loadBalancer: LoadBalancer) {}
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pick(pickArgs: PickArgs): QueuePickResult {
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if (!this.calledExitIdle) {
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process.nextTick(() => {
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this.loadBalancer.exitIdle();
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});
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this.calledExitIdle = true;
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}
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return {
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pickResultType: PickResultType.QUEUE,
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subchannel: null,
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status: null,
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onCallStarted: null,
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onCallEnded: null,
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};
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}
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}
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