Limit concurrent blocks processed

1 files changed, 51 insertions, 0 deletions

diff --git a/lib/utils/batch.js b/lib/utils/batch.js
new file mode 100644
index 0000000..5b92be5
--- /dev/null
+++ b/lib/utils/batch.js
@@ -0,0 +1,51 @@
+var Q = require("q");
+var _ = require("lodash");
+
+// Execute a method for all element
+function execEach(items, options) {
+    var concurrents = 0, d = Q.defer(), pending = [];
+
+    options = _.defaults(options || {}, {
+        max: 100,
+        fn: function(item) {}
+    });
+
+
+    function startItem(item, i) {
+        if (concurrents >= options.max) {
+            pending.push([item, i]);
+            return;
+        }
+
+        concurrents++;
+        Q()
+        .then(function() {
+            return options.fn(item, i);
+        })
+        .then(function() {
+            concurrents--;
+
+            // Next pending
+            var next = pending.shift();
+
+            if (concurrents == 0 && !next) {
+                d.resolve();
+            } else if (next) {
+                startItem.apply(null, next);
+            }
+        })
+        .fail(function(err) {
+            pending = [];
+            d.reject(err);
+        })
+    }
+
+    _.each(items, startItem);
+
+    return d.promise;
+}
+
+module.exports = {
+    execEach: execEach
+};
+