refactor: Final version of the plugin interface

After alot of back and forth I think we landed a good plugin design.

The premise was to remove event emission (since it was attached hackily throught the codebase)
and instead use explicit APIs. However the one thing error events worked well with was namespacing
issues from plugins. Which lead me to think, why on earth is that just an error thing?

So new API (again, like millionth refactor/iteration to cure itch)

```
export abstract class DeepstreamPlugin {
  public abstract description: string
  public async whenReady (): Promise<void> {}
  public init? (): void
  public async close (): Promise<void> {}
  public setRecordHandler? (recordHandler: any): void
}

```

Doesn't look very different does it? The main aspect is the fact we no longer care if its sync or not.
Plugin developers conceal that by just using whenReady (which is always async but could be a millisecond
and could be up to initialization timeout).

So what changed?

```
interface DeepstreamExamplePluginOptions {
}

class DeepstreamExample extends DeepstreamPlugin {
  public description = 'An Example Plugin'
  public logger = this.sevices.logger.getNameSpace('DEEPSTREAM_EXAMPLE_PLUGIN')

  constructor (pluginSettings: DeepstreamExamplePluginOptions, private services: DeepstreamServices) {}

  public async whenReady (): Promise<void> {
    return setTimeout(resolve, 10) // to wait for async dependencies, like opening a server, loading a file, etc
  }
  public init (): void {
    // This just allows you to move logic out of the constructor and guarantees its called after
    // the whenReady is already being waited upon.

    // If something failed, you can either
    this.logger.fatal(ERROR_EVENT, 'descriptive message')

    // or
    this.logger.error(ERROR_EVENT, 'descriptive message')
    this.services.onFatalException()
  }
  public async close (): Promise<void> {
    return setTimeout(resolve, 10) // closing a server for example
  }
}

conf/config.yml

@@ -220,7 +220,7 @@ permission:
   type: config
   options:
     # Path to the permissionFile. Can be json, js or yml
-    path: ./permissions.yml
+    path: ./permissions2.yml
     # Amount of times nested cross-references will be loaded. Avoids endless loops
     maxRuleIterations: 3
     # PermissionResults are cached to increase performance. Lower number means more loading

src/config/config-initialiser.spec.ts

@@ -3,6 +3,7 @@ import { expect } from 'chai'
 import * as path from 'path'
 import * as defaultConfig from '../default-options'
 import * as configInitialiser from './config-initialiser'
+import { EventEmitter } from 'events'
 
 describe('config-initialiser', () => {
   before(() => {
@@ -20,7 +21,7 @@ describe('config-initialiser', () => {
           options: { some: 'options' }
         }
       } as any
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.plugins.custom.description).to.equal('mock-plugin')
     })
 
@@ -32,7 +33,7 @@ describe('config-initialiser', () => {
           options: {}
         }
       } as any
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.toString()).to.equal('[object Object]')
     })
 
@@ -46,7 +47,7 @@ describe('config-initialiser', () => {
           options: { some: 'options' }
         }
       } as any
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.plugins.mock.description).to.equal('mock-plugin')
     })
   })
@@ -57,7 +58,7 @@ describe('config-initialiser', () => {
         const config = defaultConfig.get()
         config[key] = './does-not-exist'
         expect(() => {
-          configInitialiser.initialise(config)
+          configInitialiser.initialise(new EventEmitter(), config)
         }).to.throw(new Error())
       })
     })
@@ -67,7 +68,7 @@ describe('config-initialiser', () => {
 
       const config = defaultConfig.get()
       config.sslKey = './sslKey.pem'
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.config.sslKey).to.equal('I\'m a key')
     })
   })
@@ -83,7 +84,7 @@ describe('config-initialiser', () => {
         }
       } as any
       try {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       } catch (e) {
         errored = true
         expect(e.toString()).to.contain(path.join('/foobar', '@deepstream/cache-blablub'))
@@ -104,7 +105,7 @@ describe('config-initialiser', () => {
       config.auth = {
         type: 'none'
       } as any
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.authentication.description).to.equal('Open Authentication')
     })
 
@@ -118,7 +119,7 @@ describe('config-initialiser', () => {
           path: './users.json'
         }
       }
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.authentication.description).to.contain('file using')
       expect(result.services.authentication.description).to.contain(path.resolve('src/test/config/users.json'))
     })
@@ -138,7 +139,7 @@ describe('config-initialiser', () => {
         }
       }
 
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.authentication.description).to.equal('http webhook to http://some-url.com')
     })
 
@@ -148,7 +149,7 @@ describe('config-initialiser', () => {
       delete config.auth
 
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw('No authentication type specified')
     })
 
@@ -162,7 +163,7 @@ describe('config-initialiser', () => {
         }
       }
 
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       await result.services.authentication.whenReady()
     })
 
@@ -175,7 +176,7 @@ describe('config-initialiser', () => {
       }
 
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw(/Cannot find module/)
     })
 
@@ -188,7 +189,7 @@ describe('config-initialiser', () => {
       }
 
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw('Unknown authentication type bla')
     })
 
@@ -201,7 +202,7 @@ describe('config-initialiser', () => {
         options: {}
       }
 
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.authentication.description).to.equal('Open Authentication')
       delete global.deepstreamCLI
     })
@@ -218,7 +219,7 @@ describe('config-initialiser', () => {
           path: './basic-permission-config.json'
         }
       }
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.permission.description).to.contain('valve permissions loaded from')
       expect(result.services.permission.description).to.contain(path.resolve('./src/test/config/basic-permission-config.json'))
     })
@@ -233,7 +234,7 @@ describe('config-initialiser', () => {
         }
       }
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw('Unknown permission type does-not-exist')
     })
 
@@ -247,7 +248,7 @@ describe('config-initialiser', () => {
         }
       }
 
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       await result.services.permission.whenReady()
     })
 
@@ -260,7 +261,7 @@ describe('config-initialiser', () => {
       }
 
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw(/Cannot find module/)
     })
 
@@ -269,7 +270,7 @@ describe('config-initialiser', () => {
       delete config.permission
 
       expect(() => {
-        configInitialiser.initialise(config)
+        configInitialiser.initialise(new EventEmitter(), config)
       }).to.throw('No permission type specified')
     })
 
@@ -282,7 +283,7 @@ describe('config-initialiser', () => {
         options: {}
       }
 
-      const result = configInitialiser.initialise(config)
+      const result = configInitialiser.initialise(new EventEmitter(), config)
       expect(result.services.permission.description).to.equal('none')
       delete global.deepstreamCLI
     })

src/config/config-initialiser.ts

@@ -2,7 +2,7 @@ import * as fs from 'fs'
 import * as utils from '../utils/utils'
 import * as fileUtils from './file-utils'
 import { DeepstreamConfig, DeepstreamServices, ConnectionEndpoint, PluginConfig, Logger, Storage, StorageReadCallback, StorageWriteCallback, Authentication, Permission, LOG_LEVEL } from '../types'
-import { JSONObject } from '../../binary-protocol/src/message-constants'
+import { JSONObject, EVENT } from '../../binary-protocol/src/message-constants'
 import { DistributedClusterRegistry } from '../services/cluster-registry/distributed-cluster-registry'
 import { SingleClusterNode } from '../services/cluster-node/single-cluster-node'
 import { DefaultSubscriptionRegistryFactory } from '../services/subscription-registry/default-subscription-registry-factory'
@@ -21,6 +21,7 @@ import { LocalMonitoring } from '../services/monitoring/noop-monitoring'
 import { DistributedLockRegistry } from '../services/lock/distributed-lock-registry'
 import { DistributedStateRegistryFactory } from '../services/cluster-state/distributed-state-registry-factory'
 import { get as getDefaultOptions } from '../default-options'
+import Deepstream from '../deepstream.io';
 
 let commandLineArguments: any
 
@@ -62,13 +63,20 @@ export const registerPlugin = function (name: string, construct: Function) {
  * Takes a configuration object and instantiates functional properties.
  * CLI arguments will be considered.
  */
-export const initialise = function (config: DeepstreamConfig): { config: DeepstreamConfig, services: DeepstreamServices } {
+export const initialise = function (deepstream: Deepstream, config: DeepstreamConfig): { config: DeepstreamConfig, services: DeepstreamServices } {
   commandLineArguments = global.deepstreamCLI || {}
   handleUUIDProperty(config)
   handleSSLProperties(config)
   mergeConnectionOptions(config)
 
   const services = {} as DeepstreamServices
+  services.notifyFatalException = () => {
+    if (config.exitOnPluginError) {
+      process.exit(1)
+    } else {
+      deepstream.emit(EVENT.FATAL_EXCEPTION)
+    }
+  }
   services.logger = handleLogger(config, services)
 
   services.subscriptions = new (resolvePluginClass(config.subscriptions, 'subscriptions'))(config.subscriptions.options, services, config)

src/config/js-yaml-loader.ts

@@ -5,6 +5,7 @@ import * as path from 'path'
 import { get as getDefaultOptions } from '../default-options'
 import { merge } from '../utils/utils'
 import { DeepstreamConfig } from '../types'
+import Deepstream from '../deepstream.io'
 
 const configInitialiser = require('./config-initialiser')
 const fileUtils = require('./file-utils')
@@ -65,9 +66,9 @@ export const loadConfigWithoutInitialisation = function (filePath: string | null
  * Configuraiton file will be transformed to a deepstream object by evaluating
  * some properties like the plugins (logger and connectors).
  */
-export const loadConfig = function (filePath: string | null, args?: object) {
+export const loadConfig = function (deepstream: Deepstream, filePath: string | null, args?: object) {
   const config = loadConfigWithoutInitialisation(filePath, args)
-  const result = configInitialiser.initialise(config.config)
+  const result = configInitialiser.initialise(deepstream, config.config)
   return {
     config: result.config,
     services: result.services,

src/deepstream.io.ts

@@ -226,7 +226,7 @@ export class Deepstream extends EventEmitter {
   */
   private async serviceInit () {
     const readyPromises = Object.keys(this.services).reduce((promises, serviceName) => {
-      if (['connectionEndpoints', 'plugins'].includes(serviceName)) {
+      if (['connectionEndpoints', 'plugins', 'notifyFatalException'].includes(serviceName)) {
         return promises
       }
       const service = (this.services as any)[serviceName] as DeepstreamPlugin
@@ -399,12 +399,12 @@ private async pluginsShutdown () {
   private loadConfig (config: PartialDeepstreamConfig | string | null): void {
     let result
     if (config === null || typeof config === 'string') {
-      result = jsYamlLoader.loadConfig(config)
+      result = jsYamlLoader.loadConfig(this, config)
       this.configFile = result.file
     } else {
       configInitialiser.mergeConnectionOptions(config)
       const rawConfig = merge(getDefaultOptions(), config) as DeepstreamConfig
-      result = configInitialiser.initialise(rawConfig)
+      result = configInitialiser.initialise(this, rawConfig)
     }
     configValidator.validate(result.config)
     this.config = result.config