Expose libvips thread pool size

README.md

@@ -365,6 +365,18 @@ sharp.cache(200); // { current: 75, high: 99, memory: 200, items: 500 }
 sharp.cache(50, 200); // { current: 49, high: 99, memory: 50, items: 200}
 ```
 
+#### sharp.concurrency([threads])
+
+`threads`, if provided, is the Number of threads _libvips'_ should create for image processing. The default value is the number of CPU cores. A value of `0` will reset to this default.
+
+This method always returns the current concurrency.
+
+```javascript
+var threads = sharp.concurrency(); // 4
+sharp.concurrency(2); // 2
+sharp.concurrency(0); // 4
+```
+
 #### sharp.counters()
 
 Provides access to internal task counters.

index.js

@@ -430,6 +430,16 @@ module.exports.cache = function(memory, items) {
   return sharp.cache(memory, items);
 };
 
+/*
+  Get and set size of thread pool
+*/
+module.exports.concurrency = function(concurrency) {
+  if (Number.isNaN(concurrency)) {
+    concurrency = null;
+  }
+  return sharp.concurrency(concurrency);
+};
+
 /*
   Get internal counters
 */

src/sharp.cc

@@ -775,6 +775,20 @@ NAN_METHOD(cache) {
   NanReturnValue(cache);
 }
 
+/*
+  Get and set size of thread pool
+*/
+NAN_METHOD(concurrency) {
+  NanScope();
+
+  // Set concurrency
+  if (args[0]->IsInt32()) {
+    vips_concurrency_set(args[0]->Int32Value());
+  }
+  // Get concurrency
+  NanReturnValue(NanNew<Number>(vips_concurrency_get()));
+}
+
 /*
   Get internal counters (queued tasks, processing tasks)
 */
@@ -807,6 +821,7 @@ extern "C" void init(Handle<Object> target) {
   NODE_SET_METHOD(target, "metadata", metadata);
   NODE_SET_METHOD(target, "resize", resize);
   NODE_SET_METHOD(target, "cache", cache);
+  NODE_SET_METHOD(target, "concurrency", concurrency);
   NODE_SET_METHOD(target, "counters", counters);
 }
 

tests/parallel.js

@@ -8,8 +8,10 @@ var inputJpg = path.join(__dirname, "fixtures/2569067123_aca715a2ee_o.jpg"); //
 var width = 720;
 var height = 480;
 
+sharp.concurrency(1);
+
 var timer = setInterval(function() {
-  console.dir(sharp.cache());
+  console.dir(sharp.counters());
 }, 100);
 
 async.mapSeries([1, 1, 2, 4, 8, 16, 32, 64, 128], function(parallelism, next) {
@@ -33,5 +35,5 @@ async.mapSeries([1, 1, 2, 4, 8, 16, 32, 64, 128], function(parallelism, next) {
   );
 }, function() {
   clearInterval(timer);
-  console.dir(sharp.cache());
+  console.dir(sharp.counters());
 });

tests/unit.js

@@ -28,6 +28,13 @@ var inputGif = path.join(fixturesPath, "Crash_test.gif"); // http://upload.wikim
 sharp.cache(0); // Disable
 sharp.cache(50, 500); // 50MB, 500 items
 
+// Ensure concurrency can be set
+var defaultConcurrency = sharp.concurrency();
+sharp.concurrency(16);
+assert.strictEqual(16, sharp.concurrency());
+sharp.concurrency(0);
+assert.strictEqual(defaultConcurrency, sharp.concurrency());
+
 async.series([
   // Resize with exact crop
   function(done) {