open-consul/ui-v2/app/utils/dom/event-source/blocking.js

152 lines
5.6 KiB
JavaScript

import { get } from '@ember/object';
const pause = 2000;
// native EventSource retry is ~3s wait
// any specified errors here will mean that the blocking query will attempt
// a reconnection every 3s until it reconnects to Consul
export const createErrorBackoff = function(ms = 3000, P = Promise, wait = setTimeout) {
// This expects an ember-data like error
return function(err) {
const status = get(err, 'errors.firstObject.status');
if (typeof status !== 'undefined') {
switch (true) {
// Any '5xx' (not 500) errors should back off and try again
case status.indexOf('5') === 0 && status.length === 3 && status !== '500':
// fallsthrough
case status === '0':
// TODO: Move this to the view layer so we can show a connection error
// and reconnection success to the user
// Any 0 aborted connections should back off and try again
return new P(function(resolve) {
wait(function() {
resolve(err);
}, ms);
});
}
}
// any other errors should throw to be picked up by an error listener/catch
throw err;
};
};
export const validateCursor = function(current, prev = null) {
let cursor = parseInt(current);
if (!isNaN(cursor)) {
// if cursor is less than the current cursor, reset to zero
if (prev !== null && cursor < prev) {
cursor = 0;
}
// if cursor is less than 0, its always safe to use 1
return Math.max(cursor, 1);
}
};
const throttle = function(configuration, prev, current) {
return function(obj) {
return new Promise(function(resolve, reject) {
setTimeout(function() {
resolve(obj);
}, pause);
});
};
};
const defaultCreateEvent = function(result, configuration) {
return {
type: 'message',
data: result,
};
};
/**
* Wraps an EventSource with functionality to add native EventSource-like functionality
*
* @param {Class} [CallableEventSource] - CallableEventSource Class
* @param {Function} [backoff] - Default backoff function for all instances, defaults to createErrorBackoff
*/
export default function(EventSource, backoff = createErrorBackoff()) {
/**
* An EventSource implementation to add native EventSource-like functionality with just callbacks (`cursor` and 5xx backoff)
*
* This includes:
* 1. 5xx backoff support (uses a 3 second reconnect like native implementations). You can add to this via `Promise.catch`
* 2. A `cursor` configuration value. Current `cursor` is taken from the `meta` property of the event (i.e. `event.data.meta.cursor`)
* 3. Event data can be customized by adding a `configuration.createEvent`
*
* @param {Function} [source] - Promise returning function that resolves your data
* @param {Object} [configuration] - Plain configuration object:
* `cursor` - Cursor position of the EventSource
* `createEvent` - A data filter, giving you the opportunity to filter or replace the event data, such as removing/replacing records
*/
const BlockingEventSource = function(source, configuration = {}) {
const { currentEvent, ...config } = configuration;
EventSource.apply(this, [
configuration => {
const { createEvent, ...superConfiguration } = configuration;
return source
.apply(this, [superConfiguration, this])
.catch(backoff)
.then(result => {
if (result instanceof Error) {
return result;
}
const _createEvent =
typeof createEvent === 'function' ? createEvent : defaultCreateEvent;
let event = _createEvent(result, configuration);
// allow custom types, but make a default of `message`, ideally this would check for CustomEvent
// but keep this flexible for the moment
if (!event.type) {
event = {
type: 'message',
data: event,
};
}
// meta is also configurable by using createEvent
const meta = get(event.data || {}, 'meta');
if (meta) {
// pick off the `cursor` from the meta and add it to configuration
// along with cursor validation
configuration.cursor = validateCursor(meta.cursor, configuration.cursor);
configuration.cacheControl = meta.cacheControl;
}
if ((configuration.cacheControl || '').indexOf('no-store') === -1) {
this.currentEvent = event;
}
this.dispatchEvent(event);
const throttledResolve = throttle(configuration, event, this.previousEvent);
this.previousEvent = this.currentEvent;
return throttledResolve(result);
});
},
config,
]);
if (typeof currentEvent !== 'undefined') {
this.currentEvent = currentEvent;
}
// only on initialization
// if we already have an currentEvent set via configuration
// dispatch the event so things are populated immediately
this.addEventListener('open', e => {
const currentEvent = e.target.getCurrentEvent();
if (typeof currentEvent !== 'undefined') {
this.dispatchEvent(currentEvent);
}
});
};
BlockingEventSource.prototype = Object.assign(
Object.create(EventSource.prototype, {
constructor: {
value: EventSource,
configurable: true,
writable: true,
},
}),
{
// if we are having these props, at least make getters
getCurrentEvent: function() {
return this.currentEvent;
},
getPreviousEvent: function() {
return this.previousEvent;
},
}
);
return BlockingEventSource;
}