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node-memwatch: Leak Detection and Heap Diffing for Node.JS

node-memwatch is here to help you detect and find memory leaks in Node.JS code. It provides:

  • A stats event, emitted on full MarkSweepCompact GCs giving you data describing your heap usage and trends over time.

  • A HeapDiff class that lets you compare the state of your heap between two points in time, telling you what has been allocated, and what has been released.

Installation

  • npm install @airbnb/node-memwatch

Description

There are a growing number of tools for debugging and profiling memory usage in Node.JS applications, but there is still a need for a platform-independent native module that requires no special instrumentation. This module attempts to satisfy that need.

To get started, import node-memwatch like so:

varmemwatch=require('@airbnb/node-memwatch');

Leak Detection

Currently unsupported while we explore heuristics

Heap Usage

The best way to evaluate your memory footprint is to look at heap usage right after V8 performs garbage collection. memwatch does exactly this - it checks heap usage only after GC to give you a stable baseline of your actual memory usage.

When V8 performs a garbage collection (technically, we're talking about a full GC with heap compaction), memwatch will emit a stats event.

memwatch.on('stats',function(stats){ ... });

The stats data will look something like this:

{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}

V8 has its own idea of when it's best to perform a GC, and under a heavy load, it may defer this action for some time. To aid in speedier debugging, memwatch provides a gc() method to force V8 to do a full GC and heap compaction.

Heap Diffing

For leak isolation, it provides a HeapDiff class that takes two snapshots and computes a diff between them. For example:

// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();

The contents of diff will look something like:

{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}

The diff shows that during the sample period, the total number of allocated String and Array classes decreased, but Leaking Class grew by 9998 allocations. Hmmm.

You can use HeapDiff in your on('stats') callback; even though it takes a memory snapshot, which triggers a V8 GC, it will not trigger the stats event itself. Because that would be silly.

Future Work

Please see the Issues to share suggestions and contribute!

License

http://wtfpl.net

About

A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.

Resources

Readme
Activity

Stars

6 stars

Watchers

0 watching

Forks

1 fork
Report repository

Releases

Packages

Used by

Contributors

Languages

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var __re = new RegExp('^' + "github\\.com" + '
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
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Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
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var __re = new RegExp('^' + ".*" + '
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
Skip to content
BranchesTags
Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
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observer.observe(document.body, { childList: true, subtree: true });
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} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
Skip to content
BranchesTags
Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
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})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
Skip to content
BranchesTags
Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
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function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
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lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
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node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
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0 watching
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1 fork
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GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
Skip to content
BranchesTags
Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages

, 'i');
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filter: invert(1) hue-rotate(180deg) !important;
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})();
})();
GitHub - dhlolo/node-memwatch: A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks. · GitHub
Skip to content
BranchesTags
Repository files navigation
node-memwatch: Leak Detection and Heap Diffing for Node.JS
node-memwatch is here to help you detect and find memory leaks in
Node.JS code. It provides:
  • A stats event, emitted on full MarkSweepCompact GCs giving you
data describing your heap usage and trends over time.
  • A HeapDiff class that lets you compare the state of your heap between
two points in time, telling you what has been allocated, and what
has been released.
Installation
  • npm install @airbnb/node-memwatch
Description
There are a growing number of tools for debugging and profiling memory
usage in Node.JS applications, but there is still a need for a
platform-independent native module that requires no special
instrumentation. This module attempts to satisfy that need.
To get started, import node-memwatch like so:
varmemwatch=require('@airbnb/node-memwatch');
Leak Detection
Currently unsupported while we explore heuristics
Heap Usage
The best way to evaluate your memory footprint is to look at heap
usage right after V8 performs garbage collection. memwatch does
exactly this - it checks heap usage only after GC to give you a stable
baseline of your actual memory usage.
When V8 performs a garbage collection (technically, we're talking
about a full GC with heap compaction), memwatch will emit a stats
event.
memwatch.on('stats',function(stats){ ... });
The stats data will look something like this:
{gcScavengeCount: 1,gcScavengeTime: 1100880,// nsgcMarkSweepCompactCount: 2,gcMarkSweepCompactTime: 21157231,// nsgcIncrementalMarkingCount: 0,gcIncrementalMarkingTime: 0,//nsgcProcessWeakCallbacksCount: 0,gcProcessWeakCallbacksTime: 0,// nstotal_heap_size: 16097280,// bytestotal_heap_size_executable: 3670016,// bytestotal_physical_size: 10741880,// bytestotal_available_size: 1487689928,// bytesused_heap_size: 5691584,// bytesheap_size_limit: 1501560832,// bytesmalloced_memory: 8192,peak_malloced_memory: 1185464,gc_time: 4587251// ns}
V8 has its own idea of when it's best to perform a GC, and under a
heavy load, it may defer this action for some time. To aid in
speedier debugging, memwatch provides a gc() method to force V8 to
do a full GC and heap compaction.
Heap Diffing
For leak isolation, it provides a HeapDiff class that takes two snapshots and
computes a diff between them. For example:
// Take first snapshotvarhd=newmemwatch.HeapDiff();// do some things ...// Take the second snapshot and compute the diffvardiff=hd.end();
The contents of diff will look something like:
{"before": {"nodes": 11625,"size_bytes": 1869904,"size": "1.78 mb"},"after": {"nodes": 21435,"size_bytes": 2119136,"size": "2.02 mb"},"change": {"size_bytes": 249232,"size": "243.39 kb","freed_nodes": 197,"allocated_nodes": 10007,"details": [{"what": "String","size_bytes": -2120,"size": "-2.07 kb","+": 3,"-": 62},{"what": "Array","size_bytes": 66687,"size": "65.13 kb","+": 4,"-": 78},{"what": "LeakingClass","size_bytes": 239952,"size": "234.33 kb","+": 9998,"-": 0}]}}
The diff shows that during the sample period, the total number of
allocated String and Array classes decreased, but Leaking Class
grew by 9998 allocations. Hmmm.
You can use HeapDiff in your on('stats') callback; even though it
takes a memory snapshot, which triggers a V8 GC, it will not trigger
the stats event itself. Because that would be silly.
Future Work
Please see the Issues to share suggestions and contribute!
License
http://wtfpl.net
About
A NodeJS library to keep an eye on your memory usage, and discover and isolate leaks.
Resources
Readme
Activity
Stars
6 stars
Watchers
0 watching
Forks
1 fork
Report repository
Releases
Packages
Used by
Contributors
Languages