Purge idle pipelines

src/functions/demux.ts

@@ -6,6 +6,8 @@ type DemuxStreams = NodeJS.WritableStream | NodeJS.ReadWriteStream;
 
 export interface DemuxOptions extends DuplexOptions {
     remultiplex?: boolean;
+    purgeIdleInterval?: number;
+    maxIdleTime?: number;
 }
 
 export function demux(
@@ -18,12 +20,13 @@ export function demux(
 
 class Demux extends Duplex {
     private streamsByKey: {
-        [key: string]: DemuxStreams;
+        [key: string]: { stream: DemuxStreams; lastWrite: number };
     };
     private demuxer: (chunk: any) => string;
     private construct: (destKey?: string, chunk?: any) => DemuxStreams;
     private remultiplex: boolean;
     private transform: Transform;
+    private maxIdleTime: number;
     constructor(
         construct: (destKey?: string) => DemuxStreams,
         demuxBy: string | ((chunk: any) => string),
@@ -43,10 +46,25 @@ class Demux extends Duplex {
                 cb(null);
             },
         });
+        this.maxIdleTime = options.maxIdleTime || 600000;
+        const purgeIdleInterval = options.purgeIdleInterval || 600000;
+        setInterval(() => {
+            this._destroyIdle();
+        }, purgeIdleInterval);
 
         this.on("unpipe", () => this._flush());
     }
 
+    private _destroyIdle() {
+        for (let key in this.streamsByKey) {
+            const curTime = Date.now();
+            const pipeline = this.streamsByKey[key];
+
+            if (curTime - pipeline.lastWrite > this.maxIdleTime) {
+                delete this.streamsByKey[key];
+            }
+        }
+    }
     // tslint:disable-next-line
     public _read(size: number) {}
 
@@ -54,7 +72,10 @@ class Demux extends Duplex {
         const destKey = this.demuxer(chunk);
         if (this.streamsByKey[destKey] === undefined) {
             const newPipeline = await this.construct(destKey, chunk);
-            this.streamsByKey[destKey] = newPipeline;
+            this.streamsByKey[destKey] = {
+                stream: newPipeline,
+                lastWrite: Date.now(),
+            };
             if (this.remultiplex && isReadable(newPipeline)) {
                 (newPipeline as NodeJS.ReadWriteStream).pipe(this.transform);
             } else if (this.remultiplex) {
@@ -62,10 +83,12 @@ class Demux extends Duplex {
                     `Pipeline construct for ${destKey} does not implement readable interface`,
                 );
             }
+        } else {
+            this.streamsByKey[destKey].lastWrite = Date.now();
         }
 
-        if (!this.streamsByKey[destKey].write(chunk, encoding)) {
-            this.streamsByKey[destKey].once("drain", () => {
+        if (!this.streamsByKey[destKey].stream.write(chunk, encoding)) {
+            this.streamsByKey[destKey].stream.once("drain", () => {
                 cb();
             });
         } else {
@@ -76,8 +99,8 @@ class Demux extends Duplex {
     public _flush() {
         const pipelines = Object.values(this.streamsByKey);
         let totalEnded = 0;
-        pipelines.forEach(pipeline => {
-            pipeline.once("end", () => {
+        pipelines.forEach(({ stream }) => {
+            stream.once("end", () => {
                 totalEnded++;
                 if (pipelines.length === totalEnded) {
                     this.push(null);
@@ -85,12 +108,12 @@ class Demux extends Duplex {
                 }
             });
         });
-        pipelines.forEach(pipeline => pipeline.end());
+        pipelines.forEach(({ stream }) => stream.end());
     }
 
     public _destroy(error: any, cb: (error?: any) => void) {
         const pipelines = Object.values(this.streamsByKey);
-        pipelines.forEach(p => (p as any).destroy());
+        pipelines.forEach(({ stream }) => (stream as any).destroy());
         cb(error);
     }
 }

tests/demux.spec.ts

@@ -862,3 +862,42 @@ test.cb("demux() should be 'destroyable'", t => {
     fakeSource.push(input[3]);
     fakeSource.push(input[4]);
 });
+
+test.cb("Should delete idle pipelines", t => {
+    t.plan(6);
+    const input = [
+        { key: "a", visited: [] },
+        { key: "b", visited: [] },
+        { key: "b", visited: [] },
+        { key: "a", visited: [] },
+        { key: "c", visited: [] },
+        { key: "c", visited: [] },
+        { key: "c", visited: [] },
+        { key: "b", visited: [] },
+        { key: "d", visited: [] },
+    ];
+    const construct = sinon.spy((destKey: string) => {
+        const dest = map((chunk: Test) => {
+            chunk.visited.push(1);
+            return chunk;
+        });
+        t.pass();
+
+        return dest;
+    });
+
+    const demuxed = demux(construct, "key", {
+        maxIdleTime: 110,
+        purgeIdleInterval: 110,
+    });
+
+    demuxed.on("data", data => {
+        if (data.key === "d") t.end();
+    });
+
+    for (let i = 0; i < input.length; i++) {
+        setTimeout(() => {
+            demuxed.write(input[i]);
+        }, i * 100);
+    }
+});