Context:
I have an Node.js application which memory seems to very high, I don't know if that is memory leak or not, because it is reduced after certain period time, but some times on heavy load it keeps on increasing takes much longer to get reduced.
So going through the articles and couple of videos, i figured that i have to heap snapshot and analyse what is causing the memory leak.
Steps:
I have taken 4 snap shots as of now in my local to reproduce the memory leak.
Snapshot 1: 800MB
Snapshot 2: 1400MB
Snapshot 3: 1600MB
Snapshot 4: 2000+MB
When i uploaded the heapdump files to chrome dev tools I see there a lot of information but i don't know how to proceed from there.
Please check below screenshot, it says there is constructor [array] which has 687206 as shallow Size & Retained Size is 721414 in the columns, so when expanded that constructor i can see there are 4097716 constructors created ( refer the second screenshot attached below ).
Question
What does internal array [] means ? Why is there 4097716 created ?
How can a filter out the constructor which created by my app and showing me that instead of some system/v8 engine constructor ?
In the same screenshot one of the constructor uses global variable called tenantRequire function, this is custom global function which is being used internally in some places instead of normal Node.js require, I see the variable across all the constructor like "Array", "Object". This is that global tenantRequire code for reference. It is just patched require function with trycatch. Is this causing the memory leak somehow ?
Refer screenshot 3, [string] constructor it has 270303848 as shallow size. When i expanded it shows modules loaded by Node.js. Question why is this taking that much size ? & Why is my lodash modules are repeated in that string constructor ?
Without knowing much about your app and the actions that cause the high memory usage, it's hard to tell what could be the issue. Which tool did you use to record the heap snapshot? What is the sequence of operations you did when you recorded the snapshot? Could you add this information to your question?
A couple of remarks
You tagged the question with node.js and showed Chrome DevTools. That's ok. You can totally take a heap snapshot of a Node.js application and analyze it in Chrome DevTools. But since both Node.js and Chrome use the same JS engine (V8) and the same garbage collector (Orinoco), it might be a bit confusing for someone who reads the question. Just to make sure I understand it correctly: the issue is in a Node.js app, not in a browser app. And you are using Chrome just to analyze the heap snapshot. Right?
Also, you wrote that you took the snapshots to reproduce the memory leak. That's not correct. You performed some action which you thought would cause a high memory usage, recorded a heap snapshot, and later loaded the snapshot in Chrome DevTools to observe the supposed memory leak.
Trace first, profile second
Every time you suspect a performance issue, you should first use tracing to understand which functions in your applications are problematic (i.e. slow, create a lot of objects that have to be garbage-collected, etc).
Then, when you know which functions to focus on, you can profile them.
Try these visual tools
There are a few tools that can help you with tracing/profiling your app. Have a look a FlameScope (a web app) and node-clinic (a suite of tools). There is also Perfetto, but I think it's for Chrome apps, not Node.js apps.
I also highly recommend the V8 blog.
Related
I am trying to set up an environment for detecting memory leaks in my application.
App setup: Angular + Electron
Simulating app use with: Mocha + Spectron + Webdriverio
I have tests for different user scenarios that I run on freshly setup app and periodically collect memory usage of each process.
When the app is in idle, memory usage is as expected. But I have run into a problem with other test cases. It seems that when running tests with mocha, I get unexpected and unknown structures in memory. That results in a memory leak.
I have attached a screenshot below (Memory tab on dev tools), that best describes my confusion.
Snapshot 1: Taken after the app is set up (81.8 MB)
Snapshot 2: Taken after a group of tests have completed (~ 10 minutes of normal use) and the app has returned to starting state (109 MB)
Snapshot 3: Taken after I have forced GC (via "Collect Garbage" button) (108 MB)
Comparing snapshot 1 and 2, I can see where most of the memory is (~19 MB): in strings.
Inspection of retainers tells me that those strings are linked to (Global handlers)>(GC roots), selecting one of the strings and executing $0 in console results in the same output for all strings: <body>...</body>. When I hover the element, it is linked to a body of my app (for every string).
"Expanding string structure" gives me a feeling, that this is caused by some module being loaded multiple times and its references never being destroyed (my guess is that is is loaded via Module() in internal/modules/cjs/loader.js:136)?
Expanding string structure
When examining memory with "Allocation timelines", I don't find this "large string objects" under unreleased memory for same action that results in new "large string object" under "heap snapshot > comparison"
When I simulate a test scenario by hand or I simulate clicks via function in console, there is no memory leak.
All of that makes me think, I am doing or using something wrong (regarding mocha).
My questions:
Is mocha not suitable for this kind of setup (i.e. it holds some references until the app is closed)?
If a structure is retained only by (Global handlers)>(GC roots), when will it be released? I read here, that they are not something you need to worry about but in my case, they are :/
How are there multiple strings (multiple references?) that, when called via $0, all reference same DOM element (<body>)?
How come this string objects are not visible in "Allocation timelines"?
What can be the cause of this type of memory leak?
No, i don't think it is mocha related thing.
Trick is that mocha runs at nodejs side, and controls browser thru chromiumdriver using webdriver protocol (HTTP):
What i can see from strings in your snapshot it is actually some code that is send from chromedriver into your app.
I believe this is some issue of chromedriver.
This might be some injections into page when chromedriver tries to execute some commands.
You can try to cleanup cookies, local and session storage between tests, or hard reload with https://webdriver.io/docs/api/browser/reloadSession.html - but reload is pretty slow thing...
Or reload just current context with https://webdriver.io/docs/api/webdriver.html#refresh
Also you can try to manually execute some clenup js code on app side with
https://webdriver.io/docs/api/browser/execute.html
Recently I started my first project with node.js, and I can definitely say I'm loving it. Very powerful with all the modules; however, it seems I'm having a "slight" memory leak that causes my server to crash after about an hour (hit's 99-100% CPU). I've been trying to fix this problem for a while now.
Luckily, after a bit of searching, I found a popular tool called memwatch. I of course installed the module, and started logging memory usage/storage of my server's process.
Eventually, after looking through the logs, I have found the likely cause.
{
"what": "String",
"size_bytes": 9421368,
"size": "8.98 mb",
"+": 16635,
"-": 533
}
Of course, within thirty seconds this little bugger managed an increase of 9mb (very unusual). This is nice and dandy to know that my memory leak seems to be of type string, but where exactly do I go from here? Is there any way I can get more accurate results?
I looked through my code, but there really isn't a string in my code that could possibly grow like this. Is there a possibility this string isn't actually a part of my code, and more a part of node or the Socket.IO module?
Right approach. Use StrongOps (Previously Nodefly) to profile memory. Isolate type of leaking object. Look at heap retained sizes as well as the instance counts. Growing Instance counts with steady workload will point at few smoking guns.
I believe StrongOps uses memwatch + some V8 profiler/GC code under the hood. Better automation. See link - http://strongloop.com/node-js-performance/strongops/
Then used node-heapdump module, that their co-founder (core contributor Ben Noordhuis) wrote to isolate the leak down to collection object, GC roots and line of code.
See blog from Ben - http://strongloop.com/strongblog/how-to-heap-snapshots/
You can use node-heapdump module, to make a dump of the V8 heap for later inspection, so you will be able to see more accurate results.
After you will make a heapdump, analyze it with Chrome DevTools:
https://developers.google.com/chrome-developer-tools/docs/javascript-memory-profiling
As Shubhra suggested, another tool to consider in helping you diagnose your memory leak is the heap profiler of StrongOps monitoring. You can easily get started in a few steps here: http://docs.strongloop.com/display/DOC/Setting+up+StrongOps+monitoring
This will save you time from having to dig through logs and gives you a visual of what's going on in your applications heap over time, as well as comparing the String to other likely culprits causing your memory leak.
You can find more information here: http://docs.strongloop.com/display/DOC/Profiling#Profiling-Memoryprofiler
I'm creating bower package search site (everything is open sourced) and I hit the wall. I have some memory leak (or I think I have) and I honestly don't know why it is there.
You can download it and run on Your own, but simple hint will help me greatly.
I have narrowed it down to this function call here https://github.com/kamilbiela/bowereggs-backend/blob/master/main.js#L14 ( nest.fetchAndSave() ) which is all defined here: https://github.com/kamilbiela/bowereggs-backend/blob/master/lib/nest.js
Basically it downloads a package list from internet, Json.parse and inserts it into database, plus some when.js promises.
Running this function few times creates a 30mb of memory per run, that is not cleaned by garbage collector. Also note that this is my first "real" node.js project, so I'll be really grateful for any tip.
For anyone having the same problem:
https://github.com/c4milo/node-webkit-agent
After making few heap dumps I discovered that objects are garbage collected and the real memory usage isn't tied to it. I think that real memory usage is bigger because of using mongo and other non node.js stuff. Also real memory usage stabilizes at ~300mb, heap dumps at ~35mb.
I am looking after an app built with Node JS that's producing some interesting issues. It was originally running on Node JS v0.3.0 and I've since upgraded to v0.10.12. We're using Node JS to render charts on the server and we've noticed the memory usage keeps climbing chart after chart.
Q1: I've been monitoring the RES column in top for the Node JS process, is this correct or should I be monitoring something else?
I've been setting variables to null to try and reallocate memory back to the system resources (I read this somewhere as a solution) and it makes only a slight difference.
I've pushed the app all the way to 1.5gb and it then ceases to function and the process doesn't appear to die. No error messages which I found odd.
Q2: Is there anything else I can do?
Thanks
Steve
That is a massive jump in versions. You may want to share what code changes you may have made to get it working on latest stable. The api is not the same as back in v0.3, so that may be part of the problem.
If not then the issue you see it more likely from heap fragmentation than from an actual leak. In later v8 versions garbage collection is more liberal with cleanup to improve performance. (see http://code.google.com/p/chromium/issues/detail?id=112386 for some discussion on this)
You may try running the application with --max_old_space_size=32 which will limit the amount of memory v8 can use to around 32MB. Note the docs say "max size of the old generation", so it won't be exactly 32MB. Just around it, for lack of a better technical explanation.
Also you can track the amount of external memory usage with --trace_external_memory. This will allow you to know if external memory (i.e. Buffers) are being retained in your application.
You're note on the application hanging around 1.5GB would tell me you're probably on a 64-bit system. You only mentioned it ceases to function, but didn't note if the CPU is spinning during that time. Also since I don't have example code I'm not sure of what might be causing this to happen.
I'd try running on latest development (v0.11.3 at the time of this writing) and see if the issue is fixed. A lot of performance/memory enhancements are being worked on that may help your issue.
I guess you have somewhere a memory leak (in form of a closure?) that keeps the (not longer used?) diagrams(?) somewhere in memory.
The v8 sometimes needs a bit tweaking when it comes to > 1 GB of memory. Try out --noincremental_marking and/or --max_old_space_size=81920000 (if you have 8 GB available).
Check for more options with node --v8-options and go through the --trace*-parameters to find out what slows down/stops node.
I'm writing a MIDlet using LWUIT and images seem to eat up incredible amounts of memory. All the images I use are PNGs and are packed inside the JAR file. I load them using the standard Image.createImage(URL) method. The application has a number of forms and each has a couple of labels an buttons, however I am fairly certain that only the active form is kept in memory (I know it isn't very trustworthy, but Runtime.freeMemory() seems to confirm this).
The application has worked well in 240x320 resolution, but moving it to 480x640 and using appropriately larger images for UI started causing out of memory errors to show up. What the application does, among other things, is download remote images. The application seems to work fine until it gets to this point. After downloading a couple of PNGs and returning to the main menu, the out of memory error is encountered. Naturally, I looked into the amount of memory the main menu uses and it was pretty shocking. It's just two labels with images and four buttons. Each button has three images used for style.setIcon, setPressedIcon and setRolloverIcon. Images range in size from 15 to 25KB but removing two of the three images used for every button (so 8 images in total), Runtime.freeMemory() showed a stunning 1MB decrease in memory usage.
The way I see it, I either have a whole lot of memory leaks (which I don't think I do, but memory leaks aren't exactly known to be easily tracked down), I am doing something terribly wrong with image handling or there's really no problem involved and I just need to scale down.
If anyone has any insight to offer, I would greatly appreciate it.
Mobile devices are usually very low on memory. So you have to use some tricks to conserve and use memory.
We had the same problem at a project of ours and we solved it like this.
for downloaded images:
Make a cache where you put your images. If you need an image, check if it is in the cachemap, if it isn't download it and put it there, if it is, use it. if memory is full, remove the oldest image in the cachemap and try again.
for other resource images:
keep them in memory only for as long as you can see them, if you can't see them, break the reference and the gc will do the cleanup for you.
Hope this helps.
There are a few things that might be happening here:
You might have seen the memory used before garbage collection, which doesn't correspond to the actual memory used by your app.
Some third party code you are running might be pooling some internal datastructures to minimize allocation. While pooling is a viable strategy, sometimes it does look like a leak. In that case, look if there is API to 'close' or 'dispose' the objects you don't need.
Finally, you might really have a leak. In this case you need to get more details on what's going on in the emulator VM (though keep in mind that it is not necessarily the same as the phone VM).
Make sure that your emulator uses JRE 1.6 as backing JVM. If you need it to use the runtime libraries from erlyer JDK, use -Xbootclasspath:<path-to-rt.jar>.
Then, after your application gets in the state you want to see, do %JAVA_HOME%\bin\jmap -dump:format=b,file=heap.bin <pid> (if you don't know the id of your process, use jps)
Now you've got a dump of the JVM heap. You can analyze it with jhat (comes with the JDK, a bit difficult to use) or some third party profilers (my preference is YourKit - it's commercial, but they have time-limited eval licenses)
I had a similar problem with LWUIT at Java DTV. Did you try flushing the images when you don't need them anymore (getAWTImage().flush())?
Use EncodedImage and resource files when possible (resource files use EncodedImage by default. Read the javadoc for such. Other comments are also correct that you need to actually observe the amount of memory, even high RAM Android/iOS devices run out of memory pretty fast with multiple images.
Avoid scaling which effectively eliminates the EncodedImage.
Did you think of the fact, that maybe loading the same image from JAR, many times, is causing many separate image objects (with identical contents) to be created instead of reusing one instance per-individual-image? This is my first guess.