feat: content steering switching (#1427)

Author: wseymour15

src/content-steering-controller.js

@@ -66,26 +66,27 @@ class SteeringManifest {
  * https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/ section 4.4.6.6.
  * DASH: https://dashif.org/docs/DASH-IF-CTS-00XX-Content-Steering-Community-Review.pdf
  *
- * @param {Object} segmentLoader a reference to the mainSegmentLoader
+ * @param {function} xhr for making a network request from the browser.
+ * @param {function} bandwidth for fetching the current bandwidth from the main segment loader.
  */
 export default class ContentSteeringController extends videojs.EventTarget {
-  // pass a segment loader reference for throughput rate and xhr
-  constructor(segmentLoader) {
+  constructor(xhr, bandwidth) {
     super();
 
     this.currentPathway = null;
     this.defaultPathway = null;
     this.queryBeforeStart = null;
     this.availablePathways_ = new Set();
-    // TODO: Implement exclusion.
     this.excludedPathways_ = new Set();
     this.steeringManifest = new SteeringManifest();
     this.proxyServerUrl_ = null;
     this.manifestType_ = null;
     this.ttlTimeout_ = null;
     this.request_ = null;
-    this.mainSegmentLoader_ = segmentLoader;
+    this.excludedSteeringManifestURLs = new Set();
     this.logger_ = logger('Content Steering');
+    this.xhr_ = xhr;
+    this.getBandwidth_ = bandwidth;
   }
 
   /**
@@ -109,57 +110,93 @@ export default class ContentSteeringController extends videojs.EventTarget {
       this.decodeDataUriManifest_(steeringUri.substring(steeringUri.indexOf(',') + 1));
       return;
     }
-    this.steeringManifest.reloadUri = resolveUrl(baseUrl, steeringUri);
+    // With DASH queryBeforeStart, we want to use the steeringUri as soon as possible for the request.
+    this.steeringManifest.reloadUri = this.queryBeforeStart ? steeringUri : resolveUrl(baseUrl, steeringUri);
     // pathwayId is HLS defaultServiceLocation is DASH
     this.defaultPathway = steeringTag.pathwayId || steeringTag.defaultServiceLocation;
     // currently only DASH supports the following properties on <ContentSteering> tags.
-    if (this.manifestType_ === 'DASH') {
-      this.queryBeforeStart = steeringTag.queryBeforeStart || false;
-      this.proxyServerUrl_ = steeringTag.proxyServerURL;
-    }
+    this.queryBeforeStart = steeringTag.queryBeforeStart || false;
+    this.proxyServerUrl_ = steeringTag.proxyServerURL || null;
 
     // trigger a steering event if we have a pathway from the content steering tag.
     // this tells VHS which segment pathway to start with.
-    if (this.defaultPathway) {
+    // If queryBeforeStart is true we need to wait for the steering manifest response.
+    if (this.defaultPathway && !this.queryBeforeStart) {
       this.trigger('content-steering');
     }
+
+    if (this.queryBeforeStart) {
+      this.requestSteeringManifest(this.steeringManifest.reloadUri);
+    }
   }
 
   /**
    * Requests the content steering manifest and parse the response. This should only be called after
    * assignTagProperties was called with a content steering tag.
+   *
+   * @param {string} initialUri The optional uri to make the request with.
+   *    If set, the request should be made with exactly what is passed in this variable.
+   *    This scenario is specific to DASH when the queryBeforeStart parameter is true.
+   *    This scenario should only happen once on initalization.
    */
-  requestSteeringManifest() {
-    // add parameters to the steering uri
+  requestSteeringManifest(initialUri) {
     const reloadUri = this.steeringManifest.reloadUri;
+
+    if (!initialUri && !reloadUri) {
+      return;
+    }
+
     // We currently don't support passing MPD query parameters directly to the content steering URL as this requires
     // ExtUrlQueryInfo tag support. See the DASH content steering spec section 8.1.
-    const uri = this.proxyServerUrl_ ? this.setProxyServerUrl_(reloadUri) : this.setSteeringParams_(reloadUri);
 
-    this.request_ = this.mainSegmentLoader_.vhs_.xhr({
+    // This request URI accounts for manifest URIs that have been excluded.
+    const uri = initialUri || this.getRequestURI(reloadUri);
+
+    // If there are no valid manifest URIs, we should stop content steering.
+    if (!uri) {
+      this.logger_('No valid content steering manifest URIs. Stopping content steering.');
+      this.trigger('error');
+      this.dispose();
+      return;
+    }
+
+    this.request_ = this.xhr_({
       uri
-    }, (error) => {
-      // TODO: HLS CASES THAT NEED ADDRESSED:
-      // If the client receives HTTP 410 Gone in response to a manifest request,
-      // it MUST NOT issue another request for that URI for the remainder of the
-      // playback session. It MAY continue to use the most-recently obtained set
-      // of Pathways.
-      // If the client receives HTTP 429 Too Many Requests with a Retry-After
-      // header in response to a manifest request, it SHOULD wait until the time
-      // specified by the Retry-After header to reissue the request.
+    }, (error, errorInfo) => {
       if (error) {
-        // TODO: HLS RETRY CASE:
+        // If the client receives HTTP 410 Gone in response to a manifest request,
+        // it MUST NOT issue another request for that URI for the remainder of the
+        // playback session. It MAY continue to use the most-recently obtained set
+        // of Pathways.
+        if (errorInfo.status === 410) {
+          this.logger_(`manifest request 410 ${error}.`);
+          this.logger_(`There will be no more content steering requests to ${uri} this session.`);
+
+          this.excludedSteeringManifestURLs.add(uri);
+          return;
+        }
+        // If the client receives HTTP 429 Too Many Requests with a Retry-After
+        // header in response to a manifest request, it SHOULD wait until the time
+        // specified by the Retry-After header to reissue the request.
+        if (errorInfo.status === 429) {
+          const retrySeconds = errorInfo.responseHeaders['retry-after'];
+
+          this.logger_(`manifest request 429 ${error}.`);
+          this.logger_(`content steering will retry in ${retrySeconds} seconds.`);
+          this.startTTLTimeout_(parseInt(retrySeconds, 10));
+          return;
+        }
         // If the Steering Manifest cannot be loaded and parsed correctly, the
         // client SHOULD continue to use the previous values and attempt to reload
         // it after waiting for the previously-specified TTL (or 5 minutes if
         // none).
         this.logger_(`manifest failed to load ${error}.`);
-        // TODO: we may want to expose the error object here.
-        this.trigger('error');
+        this.startTTLTimeout_();
         return;
       }
       const steeringManifestJson = JSON.parse(this.request_.responseText);
 
+      this.startTTLTimeout_();
       this.assignSteeringProperties_(steeringManifestJson);
     });
   }
@@ -200,18 +237,18 @@ export default class ContentSteeringController extends videojs.EventTarget {
   setSteeringParams_(url) {
     const urlObject = new window.URL(url);
     const path = this.getPathway();
+    const networkThroughput = this.getBandwidth_();
 
     if (path) {
       const pathwayKey = `_${this.manifestType_}_pathway`;
 
       urlObject.searchParams.set(pathwayKey, path);
     }
 
-    if (this.mainSegmentLoader_.throughput.rate) {
+    if (networkThroughput) {
       const throughputKey = `_${this.manifestType_}_throughput`;
-      const rateInteger = Math.round(this.mainSegmentLoader_.throughput.rate);
 
-      urlObject.searchParams.set(throughputKey, rateInteger);
+      urlObject.searchParams.set(throughputKey, networkThroughput);
     }
     return urlObject.toString();
   }
@@ -234,44 +271,91 @@ export default class ContentSteeringController extends videojs.EventTarget {
     this.steeringManifest.priority = steeringJson['PATHWAY-PRIORITY'] || steeringJson['SERVICE-LOCATION-PRIORITY'];
     // TODO: HLS handle PATHWAY-CLONES. See section 7.2 https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/
 
-    // TODO: fully implement priority logic.
     // 1. apply first pathway from the array.
-    // 2. if first first pathway doesn't exist in manifest, try next pathway.
+    // 2. if first pathway doesn't exist in manifest, try next pathway.
     //    a. if all pathways are exhausted, ignore the steering manifest priority.
     // 3. if segments fail from an established pathway, try all variants/renditions, then exclude the failed pathway.
     //    a. exclude a pathway for a minimum of the last TTL duration. Meaning, from the next steering response,
     //       the excluded pathway will be ignored.
-    const chooseNextPathway = (pathways) => {
-      for (const path of pathways) {
+    //       See excludePathway usage in excludePlaylist().
+
+    // If there are no available pathways, we need to stop content steering.
+    if (!this.availablePathways_.size) {
+      this.logger_('There are no available pathways for content steering. Ending content steering.');
+      this.trigger('error');
+      this.dispose();
+    }
+
+    const chooseNextPathway = (pathwaysByPriority) => {
+      for (const path of pathwaysByPriority) {
         if (this.availablePathways_.has(path)) {
           return path;
         }
       }
+
+      // If no pathway matches, ignore the manifest and choose the first available.
+      return [...this.availablePathways_][0];
     };
+
     const nextPathway = chooseNextPathway(this.steeringManifest.priority);
 
     if (this.currentPathway !== nextPathway) {
       this.currentPathway = nextPathway;
       this.trigger('content-steering');
     }
-    this.startTTLTimeout_();
   }
 
   /**
    * Returns the pathway to use for steering decisions
    *
-   * @return returns the current pathway or the default
+   * @return {string} returns the current pathway or the default
    */
   getPathway() {
     return this.currentPathway || this.defaultPathway;
   }
 
+  /**
+   * Chooses the manifest request URI based on proxy URIs and server URLs.
+   * Also accounts for exclusion on certain manifest URIs.
+   *
+   * @param {string} reloadUri the base uri before parameters
+   *
+   * @return {string} the final URI for the request to the manifest server.
+   */
+  getRequestURI(reloadUri) {
+    if (!reloadUri) {
+      return null;
+    }
+
+    const isExcluded = (uri) => this.excludedSteeringManifestURLs.has(uri);
+
+    if (this.proxyServerUrl_) {
+      const proxyURI = this.setProxyServerUrl_(reloadUri);
+
+      if (!isExcluded(proxyURI)) {
+        return proxyURI;
+      }
+    }
+
+    const steeringURI = this.setSteeringParams_(reloadUri);
+
+    if (!isExcluded(steeringURI)) {
+      return steeringURI;
+    }
+
+    // Return nothing if all valid manifest URIs are excluded.
+    return null;
+  }
+
   /**
    * Start the timeout for re-requesting the steering manifest at the TTL interval.
+   *
+   * @param {number} ttl time in seconds of the timeout. Defaults to the
+   *        ttl interval in the steering manifest
    */
-  startTTLTimeout_() {
+  startTTLTimeout_(ttl = this.steeringManifest.ttl) {
     // 300 (5 minutes) is the default value.
-    const ttlMS = this.steeringManifest.ttl * 1000;
+    const ttlMS = ttl * 1000;
 
     this.ttlTimeout_ = window.setTimeout(() => {
       this.requestSteeringManifest();
@@ -300,6 +384,8 @@ export default class ContentSteeringController extends videojs.EventTarget {
    * aborts steering requests clears the ttl timeout and resets all properties.
    */
   dispose() {
+    this.off('content-steering');
+    this.off('error');
     this.abort();
     this.clearTTLTimeout_();
     this.currentPathway = null;
@@ -309,6 +395,7 @@ export default class ContentSteeringController extends videojs.EventTarget {
     this.manifestType_ = null;
     this.ttlTimeout_ = null;
     this.request_ = null;
+    this.excludedSteeringManifestURLs = new Set();
     this.availablePathways_ = new Set();
     this.excludedPathways_ = new Set();
     this.steeringManifest = new SteeringManifest();
@@ -320,6 +407,19 @@ export default class ContentSteeringController extends videojs.EventTarget {
    * @param {string} pathway the pathway string to add
    */
   addAvailablePathway(pathway) {
-    this.availablePathways_.add(pathway);
+    if (pathway) {
+      this.availablePathways_.add(pathway);
+    }
+  }
+
+  /**
+   * clears all pathways from the available pathways set
+   */
+  clearAvailablePathways() {
+    this.availablePathways_.clear();
+  }
+
+  excludePathway(pathway) {
+    return this.availablePathways_.delete(pathway);
   }
 }

src/dash-playlist-loader.js

@@ -325,7 +325,10 @@ export default class DashPlaylistLoader extends EventTarget {
 
     // live playlist staleness timeout
     this.on('mediaupdatetimeout', () => {
-      this.refreshMedia_(this.media().id);
+      // We handle live content steering in the playlist controller
+      if (!this.media().attributes.serviceLocation) {
+        this.refreshMedia_(this.media().id);
+      }
     });
 
     this.state = 'HAVE_NOTHING';

src/media-groups.js

@@ -250,13 +250,10 @@ export const onError = {
    */
   AUDIO: (type, settings) => () => {
     const {
-      segmentLoaders: { [type]: segmentLoader},
       mediaTypes: { [type]: mediaType },
       excludePlaylist
     } = settings;
 
-    stopLoaders(segmentLoader, mediaType);
-
     // switch back to default audio track
     const activeTrack = mediaType.activeTrack();
     const activeGroup = mediaType.activeGroup();
@@ -295,15 +292,12 @@ export const onError = {
    */
   SUBTITLES: (type, settings) => () => {
     const {
-      segmentLoaders: { [type]: segmentLoader},
       mediaTypes: { [type]: mediaType }
     } = settings;
 
     videojs.log.warn('Problem encountered loading the subtitle track.' +
                      'Disabling subtitle track.');
 
-    stopLoaders(segmentLoader, mediaType);
-
     const track = mediaType.activeTrack();
 
     if (track) {