Add concurrent setting

README.md

@@ -119,6 +119,7 @@ The container is locked down, so there is no networking, limited memory and CPU
     - `memory` Max memory usage of a container.  
     - `cpu` Max CPU usage of a container.  
     - `timeout` Time limit for code in milliseconds.  
-    - `prepare` Whether to run containers on setup.  
+    - `prepare` Whether to start containers on setup.  
         Setting to true will speed up the first eval, but that language might not be used.
+    - `concurrent` Number of code evaluations per language than can run at a time.  
 0. Run `node .`

config.example.json

@@ -11,5 +11,6 @@
     "memory": "256m",
     "cpus": "0.25",
     "timeout": 10000,
-    "prepare": false
+    "prepare": false,
+    "concurrent": 10
 }

src/struct/LanguageHandler.js

@@ -1,6 +1,7 @@
 const { AkairoHandler } = require('discord-akairo');
 const { Collection } = require('discord.js');
 const Language = require('./Language');
+const Queue = require('./Queue');
 const childProcess = require('child_process');
 const util = require('util');
 const path = require('path');
@@ -24,6 +25,7 @@ class LanguageHandler extends AkairoHandler {
 
         this.aliases = new Collection();
         this.containers = new Collection();
+        this.queues = new Collection();
     }
 
     register(language, filepath) {
@@ -56,6 +58,7 @@ class LanguageHandler extends AkairoHandler {
             return Promise.all(loads.map(async name => {
                 const folder = path.join(__dirname, '../../docker', name);
                 await util.promisify(childProcess.exec)(`docker build -t "1computer1/comp_iler:${name}" ${folder}`);
+                this.queues.set(id, new Queue(10));
                 if (this.client.config.prepare) {
                     await this.setupContainer(id);
                 }
@@ -89,10 +92,13 @@ class LanguageHandler extends AkairoHandler {
         this.containers.get(id).count += 1;
     }
 
-    async evalCode({ language, code, options }) {
+    evalCode({ language, code, options }) {
         const { id = language.id, env = {} } = language.runWith(options);
+        const queue = this.queues.get(id);
+        return queue.enqueue(async () => {
             const { name, count } = await this.setupContainer(id);
             this.incrementCount(id);
+
             const proc = childProcess.spawn('docker', [
                 'exec',
                 `-eCOUNT=${count}`,
@@ -108,6 +114,7 @@ class LanguageHandler extends AkairoHandler {
                 await this.kill(name);
                 throw err;
             }
+        });
     }
 
     handleSpawn(proc) {

src/struct/Queue.js

@@ -0,0 +1,38 @@
+class Queue {
+    constructor(limit) {
+        this.limit = limit;
+        this.tasks = [];
+        this.ongoing = 0;
+    }
+
+    get length() {
+        return this.tasks.length;
+    }
+
+    enqueue(task) {
+        return new Promise((resolve, reject) => {
+            this.tasks.push({ task, resolve, reject });
+            if (this.ongoing <= this.limit) {
+                this.process();
+            }
+        });
+    }
+
+    async process() {
+        this.ongoing++;
+        const { task, resolve, reject } = this.tasks.shift();
+        try {
+            const x = await task();
+            resolve(x);
+        } catch (e) {
+            reject(e);
+        }
+
+        this.ongoing--;
+        while (this.ongoing <= this.limit && this.tasks.length > 0) {
+            this.process();
+        }
+    }
+}
+
+module.exports = Queue;