From ac907dc7c158056e9b6a5cb58acd27df5c7c2670 Mon Sep 17 00:00:00 2001
From: Chocobozzz <me@florianbigard.com>
Date: Wed, 6 Apr 2022 08:50:43 +0200
Subject: Improve viewer counter

More precise, avoid weird decrease, reuse an id to federate viewers
---
 server/lib/views/shared/video-viewer-counters.ts | 176 +++++++++++++++++++++++
 1 file changed, 176 insertions(+)
 create mode 100644 server/lib/views/shared/video-viewer-counters.ts

(limited to 'server/lib/views/shared/video-viewer-counters.ts')

diff --git a/server/lib/views/shared/video-viewer-counters.ts b/server/lib/views/shared/video-viewer-counters.ts
new file mode 100644
index 000000000..941b62ed7
--- /dev/null
+++ b/server/lib/views/shared/video-viewer-counters.ts
@@ -0,0 +1,176 @@
+
+import { isTestInstance } from '@server/helpers/core-utils'
+import { logger, loggerTagsFactory } from '@server/helpers/logger'
+import { VIEW_LIFETIME } from '@server/initializers/constants'
+import { sendView } from '@server/lib/activitypub/send/send-view'
+import { PeerTubeSocket } from '@server/lib/peertube-socket'
+import { getServerActor } from '@server/models/application/application'
+import { VideoModel } from '@server/models/video/video'
+import { MVideo } from '@server/types/models'
+import { buildUUID, sha256 } from '@shared/extra-utils'
+
+const lTags = loggerTagsFactory('views')
+
+type Viewer = {
+  expires: number
+  id: string
+  lastFederation?: number
+}
+
+export class VideoViewerCounters {
+
+  // expires is new Date().getTime()
+  private readonly viewersPerVideo = new Map<number, Viewer[]>()
+  private readonly idToViewer = new Map<string, Viewer>()
+
+  private readonly salt = buildUUID()
+
+  private processingViewerCounters = false
+
+  constructor () {
+    setInterval(() => this.cleanViewerCounters(), VIEW_LIFETIME.VIEWER_COUNTER)
+  }
+
+  // ---------------------------------------------------------------------------
+
+  async addLocalViewer (options: {
+    video: MVideo
+    ip: string
+  }) {
+    const { video, ip } = options
+
+    logger.debug('Adding local viewer to video viewers counter %s.', video.uuid, { ...lTags(video.uuid) })
+
+    const viewerId = this.generateViewerId(ip, video.uuid)
+    const viewer = this.idToViewer.get(viewerId)
+
+    if (viewer) {
+      viewer.expires = this.buildViewerExpireTime()
+      await this.federateViewerIfNeeded(video, viewer)
+
+      return false
+    }
+
+    const newViewer = await this.addViewerToVideo({ viewerId, video })
+    await this.federateViewerIfNeeded(video, newViewer)
+
+    return true
+  }
+
+  async addRemoteViewer (options: {
+    video: MVideo
+    viewerId: string
+    viewerExpires: Date
+  }) {
+    const { video, viewerExpires, viewerId } = options
+
+    logger.debug('Adding remote viewer to video %s.', video.uuid, { ...lTags(video.uuid) })
+
+    await this.addViewerToVideo({ video, viewerExpires, viewerId })
+
+    return true
+  }
+
+  // ---------------------------------------------------------------------------
+
+  getViewers (video: MVideo) {
+    const viewers = this.viewersPerVideo.get(video.id)
+    if (!viewers) return 0
+
+    return viewers.length
+  }
+
+  buildViewerExpireTime () {
+    return new Date().getTime() + VIEW_LIFETIME.VIEWER_COUNTER
+  }
+
+  // ---------------------------------------------------------------------------
+
+  private async addViewerToVideo (options: {
+    video: MVideo
+    viewerId: string
+    viewerExpires?: Date
+  }) {
+    const { video, viewerExpires, viewerId } = options
+
+    let watchers = this.viewersPerVideo.get(video.id)
+
+    if (!watchers) {
+      watchers = []
+      this.viewersPerVideo.set(video.id, watchers)
+    }
+
+    const expires = viewerExpires
+      ? viewerExpires.getTime()
+      : this.buildViewerExpireTime()
+
+    const viewer = { id: viewerId, expires }
+    watchers.push(viewer)
+
+    this.idToViewer.set(viewerId, viewer)
+
+    await this.notifyClients(video.id, watchers.length)
+
+    return viewer
+  }
+
+  private async cleanViewerCounters () {
+    if (this.processingViewerCounters) return
+    this.processingViewerCounters = true
+
+    if (!isTestInstance()) logger.info('Cleaning video viewers.', lTags())
+
+    try {
+      for (const videoId of this.viewersPerVideo.keys()) {
+        const notBefore = new Date().getTime()
+
+        const viewers = this.viewersPerVideo.get(videoId)
+
+        // Only keep not expired viewers
+        const newViewers: Viewer[] = []
+
+        // Filter new viewers
+        for (const viewer of viewers) {
+          if (viewer.expires > notBefore) {
+            newViewers.push(viewer)
+          } else {
+            this.idToViewer.delete(viewer.id)
+          }
+        }
+
+        if (newViewers.length === 0) this.viewersPerVideo.delete(videoId)
+        else this.viewersPerVideo.set(videoId, newViewers)
+
+        await this.notifyClients(videoId, newViewers.length)
+      }
+    } catch (err) {
+      logger.error('Error in video clean viewers scheduler.', { err, ...lTags() })
+    }
+
+    this.processingViewerCounters = false
+  }
+
+  private async notifyClients (videoId: string | number, viewersLength: number) {
+    const video = await VideoModel.loadImmutableAttributes(videoId)
+    if (!video) return
+
+    PeerTubeSocket.Instance.sendVideoViewsUpdate(video, viewersLength)
+
+    logger.debug('Video viewers update for %s is %d.', video.url, viewersLength, lTags())
+  }
+
+  private generateViewerId (ip: string, videoUUID: string) {
+    return sha256(this.salt + '-' + ip + '-' + videoUUID)
+  }
+
+  private async federateViewerIfNeeded (video: MVideo, viewer: Viewer) {
+    // Federate the viewer if it's been a "long" time we did not
+    const now = new Date().getTime()
+    const federationLimit = now - (VIEW_LIFETIME.VIEWER_COUNTER / 2)
+
+    if (viewer.lastFederation && viewer.lastFederation > federationLimit) return
+
+    await sendView({ byActor: await getServerActor(), video, type: 'viewer', viewerIdentifier: viewer.id })
+    viewer.lastFederation = now
+  }
+}
-- 
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