Add libavfilter command and improved control over FFmpeg's resource u…

…sage

.env.example

@@ -54,7 +54,10 @@ API_TYPE=none
 # Put ID of server to limit owner-only commands to
 ADMIN_SERVER=
 
-# Maximum number of media processing operations that can be running concurrently at any given time.
+# Maximum amount of physical memory FFmpeg is allowed to use, in bytes
+FFMPEG_MEMORY_LIMIT=1Gi
+
+# Maximum number of media processing operations that can be running concurrently at any given time
 MEDIA_CONCURRENCY_LIMIT=1
 
 # Maximum size in pixels for each dimension of an output video
@@ -63,4 +66,7 @@ MAX_VIDEO_DIMENSIONS=1024
 # (The size of the output file is slightly bigger than this value.)
 MAX_VIDEO_SIZE=64Mi
 # Stop processing a video after the following time (in milliseconds) has elapsed
-VIDEO_TIMEOUT=60000
+VIDEO_SOFT_TIMEOUT=60000
+# Forcefully stop processing a video after the following time (in milliseconds) has elapsed
+# (The output file might get corrupted if this time is reached.)
+VIDEO_HARD_TIMEOUT=70000

app.js

@@ -39,6 +39,7 @@ import { reload, connect, connected } from "./utils/soundplayer.js";
 // events
 import { endBroadcast, startBroadcast } from "./utils/misc.js";
 import { parseThreshold } from "./utils/tempimages.js";
+import { parseNumberWithMultipliers } from "./utils/number-parsing.js";
 
 const { types } = JSON.parse(readFileSync(new URL("./config/commands.json", import.meta.url)));
 const esmBotVersion = JSON.parse(readFileSync(new URL("./package.json", import.meta.url))).version;
@@ -108,6 +109,12 @@ esmBot ${esmBotVersion} (${process.env.GIT_REV})
     await parseThreshold();
   }
 
+  if (process.env.FFMPEG_MEMORY_LIMIT) {
+    process.env.FFMPEG_MEMORY_LIMIT = parseNumberWithMultipliers(process.env.FFMPEG_MEMORY_LIMIT);
+  } else {
+    logger.warn("FFMPEG_MEMORY_LIMIT is unset. FFmpeg's memory usage will not be limited.");
+  }
+
   // register commands and their info
   logger.log("info", "Attempting to load commands...");
   for await (const commandFile of getFiles(resolve(dirname(fileURLToPath(import.meta.url)), "./commands/"))) {
@@ -228,4 +235,10 @@ esmBot ${esmBotVersion} (${process.env.GIT_REV})
   client.connect();
 }
 
-init();
+init();
+
+function stop() {
+  process.exit();
+}
+process.once("SIGINT", stop);
+process.once("SIGTERM", stop);

classes/mediaCommand.js

@@ -21,6 +21,13 @@ export const ffmpegConfig = {
 // const limiter = new ConcurrencyLimiter(Number.parseInt(process.env.MEDIA_CONCURRENCY_LIMIT));
 const limiter = new ConcurrencyLimiter(1);
 
+const childProcesses = new Set();
+process.on("exit", () => {
+  for (const child of childProcesses) {
+    child.kill("SIGKILL");
+  }
+});
+
 class MediaCommand extends Command {
   async criteria() {
     return true;
@@ -83,43 +90,58 @@ class MediaCommand extends Command {
     }
 
     return limiter.runWhenFree(async () => {
-      if (media.mediaType === "video") {
+      if (this.params === undefined || media.mediaType === "video") {
+        const params = this.ffmpegParams(media.url);
+        // TODO: Stream the data from FFmpeg directly to Discord and to a file in TEMPDIR. If
+        // there is an error, abort the request and remove the file. If the request body exceeds
+        // 8MiB, abort the request and, when processing has finished, send the embed with the
+        // link to TMP_DOMAIN and keep the file. If there is no error and the request doesn't
+        // exceed 8MiB, remove the file.
+
+        const softTimeout = setTimeout(() => {
+          promise.child.kill("SIGTERM");
+        }, Number.parseInt(process.env.VIDEO_SOFT_TIMEOUT));
+        const hardTimeout = setTimeout(() => {
+          promise.child.kill("SIGKILL");
+        }, Number.parseInt(process.env.VIDEO_HARD_TIMEOUT));
+
+        const output = await execFileP("ffmpeg/ffmpeg", [
+          // Global options
+          "-y", "-nostats", "-nostdin", "-hide_banner", ...(process.env.FFMPEG_MEMORY_LIMIT ? ["-memorylimit", process.env.FFMPEG_MEMORY_LIMIT] : []),
+          // Input
+          "-i", media.url,
+          // Filter
+          "-vf", `fps=25, scale='min(${process.env.MAX_VIDEO_DIMENSIONS},iw)':'min(${process.env.MAX_VIDEO_DIMENSIONS},ih)':force_original_aspect_ratio=decrease:sws_flags=fast_bilinear, ${params.filterGraph}, scale='min(${process.env.MAX_VIDEO_DIMENSIONS},iw)':'min(${process.env.MAX_VIDEO_DIMENSIONS},ih)':force_original_aspect_ratio=decrease:sws_flags=fast_bilinear`,
+          // Video encoding
+          "-c:v", "libvpx", "-minrate", "500k", "-b:v", "2000k", "-maxrate", "5000k", "-cpu-used", "5", "-auto-alt-ref", "0",
+          // Audio encoding
+          "-c:a", "libopus", "-b:a", "64000",
+          // Output
+          "-fs", process.env.MAX_VIDEO_SIZE, "-f", "webm", "/tmp/output.webm",
+        ]);
+        childProcesses.add(promise.child);
+
         try {
-          const params = this.ffmpegParams(media.url);
-          // TODO: Stream the data from FFmpeg directly to Discord and to a file in TEMPDIR. If
-          // there is an error, abort the request and remove the file. If the request body exceeds
-          // 8MiB, abort the request and, when processing has finished, send the embed with the
-          // link to TMP_DOMAIN and keep the file. If there is no error and the request doesn't
-          // exceed 8MiB, remove the file.
-          const output = await execFileP("ffmpeg/ffmpeg", [
-            // Global options
-            "-y", "-nostats",
-            // Input
-            "-i", media.url,
-            // Filter
-            "-vf", `fps=25, scale='min(${process.env.MAX_VIDEO_DIMENSIONS},iw)':'min(${process.env.MAX_VIDEO_DIMENSIONS},ih)':force_original_aspect_ratio=decrease:sws_flags=fast_bilinear, ${params.filterGraph}, scale='min(${process.env.MAX_VIDEO_DIMENSIONS},iw)':'min(${process.env.MAX_VIDEO_DIMENSIONS},ih)':force_original_aspect_ratio=decrease:sws_flags=fast_bilinear`,
-            // Video encoding
-            "-c:v", "libvpx", "-minrate", "500k", "-b:v", "2000k", "-maxrate", "5000k", "-cpu-used", "5", "-auto-alt-ref", "0",
-            // Audio encoding
-            "-c:a", "libopus", "-b:a", "64000",
-            // Output
-            "-fs", process.env.MAX_VIDEO_SIZE, "-f", "webm", "/tmp/output.webm",
-          ], {
-            // TODO: Send a SIGKILL some seconds after the timeout in case FFmpeg hangs
-            timeout: Number.parseInt(process.env.VIDEO_TIMEOUT)
-          });
-          return {
-            contents: await readFile("/tmp/output.webm"),
-            name: "output.webm"
+          await promise;
+        } catch (err) {
+          if (err.code !== 255) {
+            throw err.stderr;
           }
         } finally {
+          childProcesses.delete(promise.child);
+          clearTimeout(softTimeout);
+          clearTimeout(hardTimeout);
           try {
             if (status) await status.delete();
           } catch {
             // no-op
           }
           runningCommands.delete(this.author.id);
         }
+        return {
+          contents: await readFile("/tmp/output.webm"),
+          name: "output.webm"
+        };
       } else {
         imageParams.path = media.path;
         imageParams.params.type = media.type;

commands/media-editing/lavfilter.js

@@ -0,0 +1,23 @@
+import MediaCommand from "../../classes/mediaCommand.js";
+
+class LavfilterCommand extends MediaCommand {
+  ffmpegParams(url) {
+    const newArgs = this.options.text ?? this.args.filter(item => !item.includes(url)).join(" ");
+    return {
+      filterGraph: newArgs
+    };
+  }
+
+  static description = "Processes a video using a libavfilter filtergraph. See <https://ffmpeg.org/ffmpeg-filters.html>.";
+  static aliases = ["lavfi"];
+  static arguments = ["[filtergraph description]"];
+
+  static requiresText = true;
+  static noText = "You need to provide a filtergraph description!";
+  static noImage = "You need to provide an image/GIF to generate a meme!";
+  static command = "libavfilter";
+
+  static acceptsVideo = true;
+}
+
+export default LavfilterCommand;