Henry and the Great Gorilla

lib/resource-pool.js

@@ -1,4 +1,5 @@
 var Registry = require("./registry"),
+    Semaphore = require('./semaphore'),
     inherits = require("inherits"),
     id = require("./simple-id");
 /**
@@ -13,22 +14,66 @@ var ResourcePool = module.exports = function(options) {
   ResourcePool.super.apply(this);
   this.min = options.min;
   this.max = options.max;
+  this.lockTimeout = options.lockTimeout? options.lockTimeout * 1000 : 0
+  this.maxIdle = options.maxIdle || 0
+
+  // clamp the max idle to at least the min.
+  if (this.maxIdle !== 0 && this.maxIdle < this.min) {
+    this.maxIdle = this.min;
+  }
+
+  var me = this;
 
   //allow bolt-on createResource providers via configuration
   //NOTE: any supplied options.createResource function will
   //override any class-level implementation
   if (typeof options.createResource === "function") {
     this.createResource = options.createResource;
   }
+  if (typeof options.createResourceAsync === "function") {
+    this.createResourceAsync = options.createResourceAsync;
+  }
 
   //init the min number of resources
   if (this.min) {
     for (var i = 0; i < this.min; i++) {
-      this.add(this.createResource());
+      if (this.createResourceAsync) {
+        this.createResourceAsync(function(err, resource) {
+          if (err) {
+            // Uh oh!
+          } else {
+            me.add(resource);
+          }
+        });
+      } else {
+        this.add(this.createResource());
+      }
     }
   }
 };
 
+var lockResource = function(pool, resource) {
+  resource.locked = true;
+  if (pool.lockTimeout > 0) {
+    resource.lockTimer = setTimeout(function() {
+
+      // don't mark it as unlocked, or it could get reallocated.  Just remove it from the pool and dispose it.
+      pool.fire('resourceTimeout', { id: resource.id });
+      pool.remove(resource)
+      if (resource.dispose) {
+        resource.dispose()
+      }
+    }, pool.lockTimeout)
+  }
+};
+
+var unlockResource = function(resource) {
+  resource.locked = false;
+  if (resource.lockTimer) {
+    clearTimeout(resource.lockTimer);
+  }
+};
+
 /**
  * Default implementation just returns an empty object. This makes this class useable
  * as a simple throttling mechanism for parallel processes. Override createResource
@@ -48,15 +93,29 @@ ResourcePool.prototype.getResource = function(cb) {
     return !item.locked;
   });
   if (resource) {
-    resource.locked = true;
+    lockResource(me, resource)
     cb(resource);
   } else {
     //if we're not yet at the max for this pool, create a new resource
     if (this.items.length < this.max) {
-      resource = this.createResource();
-      resource.locked = true;
-      this.add(resource);
-      cb(resource);
+      var resource;
+      var sem = new Semaphore(function() {
+        lockResource(me, resource)
+        me.add(resource);
+        me.fire('resourceAllocated', {id: resource.id});
+        cb(resource);
+      });
+      sem.increment();
+      if (me.createResourceAsync) {
+        sem.increment();
+        me.createResourceAsync(function(err, res) {
+          resource = res;
+          sem.execute();
+        })
+      } else {
+        resource = this.createResource();
+      }
+      sem.execute();
     } else {
       //now we have to wait until one is freed up
       this.once("resourceReleased", function(args) {
@@ -76,6 +135,9 @@ ResourcePool.prototype.getStats = function(cb) {
   cb({
     min: me.min,
     max: me.max,
+    active: me.items.length,
+    locked: lockCount,
+    unlocked: me.items.length - lockCount,
     available: me.max - lockCount
   })
 };
@@ -85,8 +147,27 @@ ResourcePool.prototype.getStats = function(cb) {
  * @param {Object} resource
  */
 ResourcePool.prototype.release = function(resource) {
-  resource.locked = false;
-  this.fire("resourceReleased");
+  var me = this;
+  unlockResource(resource);
+  me.fire("resourceReleased", {id: resource.id});
+
+  // clean up extras
+  me.getStats(function(stats) {
+    if (stats.unlocked > me.maxIdle) {
+      var extra = stats.unlocked - me.maxIdle
+      if (extra > me.min) {
+        for (var i = 0; i < extra; i++) {
+          var resource = me.find(function(item) {
+            return !item.locked;
+          });
+          if (resource) {
+            me.remove(resource);
+            if (resource.dispose) resource.dispose();
+          }
+        }
+      }
+    }
+  });
 };
 
 ResourcePool.prototype.dispose = function() {