Permalink
Browse files

nextTick: Handle tick callbacks after each tick

  • Loading branch information...
1 parent 0109a9f commit 4e5fe2d45aef5aacf4a6c6c2db28f0b9cc64f123 @isaacs isaacs committed Jul 14, 2012
Showing with 113 additions and 21 deletions.
  1. +42 −19 src/node.js
  2. +64 −0 test/simple/test-next-tick-intentional-starvation.js
  3. +7 −2 test/simple/test-process-active-wraps.js
View
@@ -239,6 +239,8 @@
if (domain) domain.exit();
+ // process the nextTicks after each time we get called.
+ process._tickCallback();
return ret;
};
};
@@ -247,8 +249,19 @@
var nextTickQueue = [];
var nextTickIndex = 0;
var inTick = false;
+ var tickDepth = 0;
+
+ // the maximum number of times it'll process something like
+ // nextTick(function f(){nextTick(f)})
+ // It's unlikely, but not illegal, to hit this limit. When
+ // that happens, it yields to libuv's tick spinner.
+ // This is a loop counter, not a stack depth, so we aren't using
+ // up lots of memory here. I/O can sneak in before nextTick if this
+ // limit is hit, which is not ideal, but not terrible.
+ process.maxTickDepth = 1000;
function tickDone() {
+ tickDepth = 0;
nextTickQueue.splice(0, nextTickIndex);
nextTickIndex = 0;
inTick = false;
@@ -259,28 +272,38 @@
process._tickCallback = function() {
if (inTick) return;
- var nextTickLength = nextTickQueue.length;
- if (nextTickLength === 0) return;
inTick = true;
- while (nextTickIndex < nextTickLength) {
- var tock = nextTickQueue[nextTickIndex++];
- var callback = tock.callback;
- if (tock.domain) {
- if (tock.domain._disposed) continue;
- tock.domain.enter();
- }
- var threw = true;
- try {
- callback();
- threw = false;
- } finally {
- if (threw) tickDone();
- }
- if (tock.domain) {
- tock.domain.exit();
+ // always do this at least once. otherwise if process.maxTickDepth
+ // is set to some negative value, we'd never process any of them.
+ do {
+ tickDepth++;
+ var nextTickLength = nextTickQueue.length;
+ if (nextTickLength === 0) return tickDone();
+ while (nextTickIndex < nextTickLength) {
+ var tock = nextTickQueue[nextTickIndex++];
+ var callback = tock.callback;
+ if (tock.domain) {
+ if (tock.domain._disposed) continue;
+ tock.domain.enter();
+ }
+ var threw = true;
+ try {
+ callback();
+ threw = false;
+ } finally {
+ if (threw) tickDone();
+ }
+ if (tock.domain) {
+ tock.domain.exit();
+ }
}
- }
+ nextTickQueue.splice(0, nextTickIndex);
+ nextTickIndex = 0;
+
+ // continue until the max depth or we run out of tocks.
+ } while (tickDepth < process.maxTickDepth &&
+ nextTickQueue.length > 0);
tickDone();
};
@@ -0,0 +1,64 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+
+// this is the inverse of test-next-tick-starvation.
+// it verifies that process.nextTick will *always* come before other
+// events, up to the limit of the process.maxTickDepth value.
+
+// WARNING: unsafe!
+process.maxTickDepth = Infinity;
+
+var ran = false;
+var starved = false;
+var start = +new Date();
+var timerRan = false;
+
+function spin() {
+ ran = true;
+ var now = +new Date();
+ if (now - start > 100) {
+ console.log('The timer is starving, just as we planned.');
+ starved = true;
+
+ // now let it out.
+ return;
+ }
+
+ process.nextTick(spin);
+}
+
+function onTimeout() {
+ if (!starved) throw new Error('The timer escaped!');
+ console.log('The timer ran once the ban was lifted');
+ timerRan = true;
+}
+
+spin();
+setTimeout(onTimeout, 50);
+
+process.on('exit', function() {
+ assert.ok(ran);
+ assert.ok(starved);
+ assert.ok(timerRan);
+});
@@ -46,11 +46,16 @@ function expect(activeHandles, activeRequests) {
expect(2, 1); // client handle doesn't shut down until next tick
})();
+// Force the nextTicks to be deferred to a later time.
+process.maxTickDepth = 1;
+
process.nextTick(function() {
process.nextTick(function() {
process.nextTick(function() {
- // the handles should be gone but the connect req could still be alive
- assert.equal(process._getActiveHandles().length, 0);
+ process.nextTick(function() {
+ // the handles should be gone but the connect req could still be alive
+ assert.equal(process._getActiveHandles().length, 0);
+ });
});
});
});

0 comments on commit 4e5fe2d

Please sign in to comment.