fix(pool): added optional setting for killing processes and not retaining them

REFERENCE.md

@@ -105,6 +105,7 @@ interface AdvancedSettings {
   retryProcessDelay: number = 5000; // delay before processing next job in case of internal error.
   backoffStrategies: {}; // A set of custom backoff strategies keyed by name.
   drainDelay: number = 5; // A timeout for when the queue is in drained state (empty waiting for jobs).
+  reuseProcesses: boolean = true; // Flag if true then child processes are kept for each processor, false kills child processes after finish
 }
 ```
 

lib/process/child-pool.js

@@ -13,6 +13,9 @@ const ChildPool = function ChildPool() {
     return new ChildPool();
   }
 
+  // Flag for keeping or killing processes after finished processing, default keep always
+  this.reuseProcesses = true;
+
   this.retained = {};
   this.free = {};
 };
@@ -39,6 +42,10 @@ const convertExecArgv = function(execArgv) {
   });
 };
 
+ChildPool.prototype.setReuseProcesses = function(reuseProcesses) {
+  this.reuseProcesses = reuseProcesses;
+}
+
 ChildPool.prototype.retain = function(processFile) {
   const _this = this;
   let child = _this.getFree(processFile).pop();
@@ -65,8 +72,12 @@ ChildPool.prototype.retain = function(processFile) {
 };
 
 ChildPool.prototype.release = function(child) {
-  delete this.retained[child.pid];
-  this.getFree(child.processFile).push(child);
+  if (this.reuseProcesses === true) {
+    delete this.retained[child.pid];
+    this.getFree(child.processFile).push(child);
+  } else {
+    this.kill(child);
+  }
 };
 
 ChildPool.prototype.remove = function(child) {

lib/queue.js

@@ -211,7 +211,8 @@ const Queue = function Queue(name, url, opts) {
     guardInterval: 5000,
     retryProcessDelay: 5000,
     drainDelay: 5,
-    backoffStrategies: {}
+    backoffStrategies: {},
+    reuseProcesses: true
   });
 
   this.settings.lockRenewTime =
@@ -650,6 +651,7 @@ Queue.prototype.setHandler = function(name, handler) {
     }
 
     this.childPool = this.childPool || require('./process/child-pool')();
+    this.childPool.setReuseProcesses(this.settings.reuseProcesses);
 
     const sandbox = require('./process/sandbox');
     this.handlers[name] = sandbox(handler, this.childPool).bind(this);

test/test_child-pool.js

@@ -141,4 +141,18 @@ describe('Child pool', () => {
         expect(children).to.include(child);
       });
   });
+
+  it('should kill child after processing is finished and not retain it', function() {
+    const processor = __dirname + '/fixtures/fixture_processor_bar.js';
+
+    pool.setReuseProcesses(false);
+
+    return pool.retain(processor).then(_child => {
+      expect(_child).to.be.ok;
+      pool.release(_child);
+
+      expect(pool.retained).to.be.empty;
+      expect(pool.free[processor]).to.be.empty;
+    });
+  });
 });