From 5d392effccd7da2584bfee4ef8cd6d565deff8a5 Mon Sep 17 00:00:00 2001
From: Thomas Hobson <git@hexf.me>
Date: Fri, 1 Oct 2021 20:28:54 +1300
Subject: [PATCH] api: maximum concurrent jobs and potential fix for gcc

---
 api/src/config.js     |  7 +++++++
 api/src/job.js        | 38 +++++++++++++++++++++++++++++++-------
 docs/configuration.md |  9 +++++++++
 3 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/api/src/config.js b/api/src/config.js
index 84270aa..bbd7ae9 100644
--- a/api/src/config.js
+++ b/api/src/config.js
@@ -114,6 +114,13 @@ const options = [
             'https://github.com/engineer-man/piston/releases/download/pkgs/index',
         validators: [],
     },
+    {
+        key: 'max_concurrent_jobs',
+        desc: 'Maximum number of concurrent jobs to run at one time',
+        default: 64,
+        parser: parse_int,
+        validators: [(x) => x > 0 || `${x} cannot be negative`]
+    }
 ];
 
 logger.info(`Loading Configuration from environment`);
diff --git a/api/src/job.js b/api/src/job.js
index 683cda6..712dcd8 100644
--- a/api/src/job.js
+++ b/api/src/job.js
@@ -16,6 +16,19 @@ const job_states = {
 let uid = 0;
 let gid = 0;
 
+let remainingJobSpaces = config.max_concurrent_jobs;
+let jobQueue = [];
+
+
+setInterval(()=>{
+    // Every 10ms try resolve a new job, if there is an available slot
+    if(jobQueue.length > 0 && remainingJobSpaces > 0){
+        jobQueue.shift()()
+    }
+}, 10)
+
+
+
 class Job {
     constructor({ runtime, files, args, stdin, timeouts, memory_limits }) {
         this.uuid = uuidv4();
@@ -48,8 +61,15 @@ class Job {
     }
 
     async prime() {
-        logger.info(`Priming job uuid=${this.uuid}`);
+        if(remainingJobSpaces < 1){
+            logger.info(`Awaiting job slot uuid=${this.uuid}`)
+            await new Promise((resolve)=>{
+                jobQueue.push(resolve)
+            })
+        }
 
+        logger.info(`Priming job uuid=${this.uuid}`);
+        remainingJobSpaces--;
         logger.debug('Writing files to job cache');
 
         logger.debug(`Transfering ownership uid=${this.uid} gid=${this.gid}`);
@@ -152,21 +172,23 @@ class Job {
                 }
             });
 
-            const exit_cleanup = () => {
+            const exit_cleanup = async () => {
                 clear_timeout(kill_timeout);
 
                 proc.stderr.destroy();
                 proc.stdout.destroy();
+
+                await this.cleanup_processes()
             };
 
-            proc.on('exit', (code, signal) => {
-                exit_cleanup();
+            proc.on('exit', async (code, signal) => {
+                await exit_cleanup();
 
                 resolve({stdout, stderr, code, signal, output });
             });
 
-            proc.on('error', err => {
-                exit_cleanup();
+            proc.on('error', async err => {
+                await exit_cleanup();
 
                 reject({ error: err, stdout, stderr, output });
             });
@@ -339,11 +361,13 @@ class Job {
     async cleanup() {
         logger.info(`Cleaning up job uuid=${this.uuid}`);
 
-        await this.cleanup_processes();
         await this.cleanup_filesystem();
+
+        remainingJobSpaces++;
     }
 }
 
+
 module.exports = {
     Job,
 };
diff --git a/docs/configuration.md b/docs/configuration.md
index 1388e9d..16a5df0 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -145,3 +145,12 @@ default: https://github.com/engineer-man/piston/releases/download/pkgs/index
 ```
 
 URL for repository index, where packages will be downloaded from.
+
+## Maximum Concurrent Jobs
+
+```yaml
+key: PISTON_MAX_CONCURRENT_JOBS
+default: 64
+```
+
+Maximum number of jobs to run concurrently.