timers: truncate decimal values

Reverts some timers behavior back to as it was before
2930bd1317d15d12738a4896c0a6c05700411b47

That commit introduced an unintended change which allowed non-integer
timeouts to actually exist since the value is no longer converted to an
integer via a TimeWrap handle directly.

Even with the fix in
e9de43549843da9f4f081cce917945878967df7
non-integer timeouts are still indeterministic, because libuv does not
support them.

This fixes the issue by emulating the old behavior:
truncate the `_idleTimeout` before using it.

See comments in
https://github.com/nodejs/node/pull/24214
for more background on this.

PR-URL: https://github.com/nodejs/node/pull/24819
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/timers.js b/lib/timers.js
index 0937e73c4a..14151d6d81 100644
--- a/lib/timers.js
+++ b/lib/timers.js
@@ -193,10 +193,13 @@ exports._unrefActive = function(item) {
 // Appends a timer onto the end of an existing timers list, or creates a new
 // list if one does not already exist for the specified timeout duration.
 function insert(item, refed, start) {
-  const msecs = item._idleTimeout;
+  let msecs = item._idleTimeout;
   if (msecs < 0 || msecs === undefined)
     return;
 
+  // Truncate so that accuracy of sub-milisecond timers is not assumed.
+  msecs = Math.trunc(msecs);
+
   item._idleStart = start;
 
   // Use an existing list if there is one, otherwise we need to make a new one.
@@ -378,7 +381,9 @@ function unenroll(item) {
   // clearTimeout that makes it clear that the list should not be deleted.
   // That function could then be used by http and other similar modules.
   if (item[kRefed]) {
-    const list = lists[item._idleTimeout];
+    // Compliment truncation during insert().
+    const msecs = Math.trunc(item._idleTimeout);
+    const list = lists[msecs];
     if (list !== undefined && L.isEmpty(list)) {
       debug('unenroll: list empty');
       queue.removeAt(list.priorityQueuePosition);