Node.js heap out of memory


Today I ran my script for filesystem indexing to refresh RAID files index and after 4h it crashed with following error:

[md5:]  241613/241627 97.5%  
[md5:]  241614/241627 97.5%  
[md5:]  241625/241627 98.1%
Creating missing list... (79570 files missing)
Creating new files list... (241627 new files)

<--- Last few GCs --->

11629672 ms: Mark-sweep 1174.6 (1426.5) -> 1172.4 (1418.3) MB, 659.9 / 0 ms [allocation failure] [GC in old space requested].
11630371 ms: Mark-sweep 1172.4 (1418.3) -> 1172.4 (1411.3) MB, 698.9 / 0 ms [allocation failure] [GC in old space requested].
11631105 ms: Mark-sweep 1172.4 (1411.3) -> 1172.4 (1389.3) MB, 733.5 / 0 ms [last resort gc].
11631778 ms: Mark-sweep 1172.4 (1389.3) -> 1172.4 (1368.3) MB, 673.6 / 0 ms [last resort gc].

<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x3d1d329c9e59 <JS Object>
1: SparseJoinWithSeparatorJS(aka SparseJoinWithSeparatorJS) [native array.js:~84] [pc=0x3629ef689ad0] (this=0x3d1d32904189 <undefined>,w=0x2b690ce91071 <JS Array[241627]>,L=241627,M=0x3d1d329b4a11 <JS Function ConvertToString (SharedFunctionInfo 0x3d1d3294ef79)>,N=0x7c953bf4d49 <String[4]\: ,\n  >)
2: Join(aka Join) [native array.js:143] [pc=0x3629ef616696] (this=0x3d1d32904189 <undefin...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [/usr/bin/node]
 2: 0xe2c5fc [/usr/bin/node]
 3: v8::Utils::ReportApiFailure(char const*, char const*) [/usr/bin/node]
 4: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [/usr/bin/node]
 5: v8::internal::Factory::NewRawTwoByteString(int, v8::internal::PretenureFlag) [/usr/bin/node]
 6: v8::internal::Runtime_SparseJoinWithSeparator(int, v8::internal::Object**, v8::internal::Isolate*) [/usr/bin/node]
 7: 0x3629ef50961b

Server is equipped with 16gb RAM and 24gb SSD swap. I highly doubt my script exceeded 36gb of memory. At least it shouldn't

Script creates index of files stored as Array of Objects with files metadata (modification dates, permissions, etc, no big data)

Here's full script code:

I've already experiend weird node issues in the past with this script what forced me eg. split index into multiple files as node was glitching when working on such big files as String. Is there any way to improve nodejs memory management with huge datasets?

7/25/2016 2:45:21 AM

Accepted Answer

If I remember correctly, there is a strict standard limit for the memory usage in V8 of around 1.7 GB, if you do not increase it manually.

In one of our products we followed this solution in our deploy script:

 node --max-old-space-size=4096 yourFile.js

There would also be a new space command but as I read here: a-tour-of-v8-garbage-collection the new space only collects the newly created short-term data and the old space contains all referenced data structures which should be in your case the best option.

6/2/2017 2:21:41 PM

Just in case anyone runs into this in an environment where they cannot set node properties directly (in my case a build tool):

NODE_OPTIONS="--max-old-space-size=4096" node ...

You can set the node options using an environment variable if you cannot pass them on the command line.


If you want to increase the memory usage of the node globally - not only single script, you can export environment variable, like this:
export NODE_OPTIONS=--max_old_space_size=4096

Then you do not need to play with files when running builds like npm run build.


I encountered this issue when trying to debug with VSCode, so just wanted to add this is how you can add the argument to your debug setup.

You can add it to the runtimeArgs property of your config in launch.json.

See example below.

"version": "0.2.0",
"configurations": [{
        "type": "node",
        "request": "launch",
        "name": "Launch Program",
        "program": "${workspaceRoot}\\server.js"
        "type": "node",
        "request": "launch",
        "name": "Launch Training Script",
        "program": "${workspaceRoot}\\training-script.js",
        "runtimeArgs": [

Here are some flag values to add some additional info on how to allow more memory when you start up your node server.

1GB - 8GB

#increase to 1gb
node --max-old-space-size=1024 index.js

#increase to 2gb
node --max-old-space-size=2048 index.js 

#increase to 3gb
node --max-old-space-size=3072 index.js

#increase to 4gb
node --max-old-space-size=4096 index.js

#increase to 5gb
node --max-old-space-size=5120 index.js

#increase to 6gb
node --max-old-space-size=6144 index.js

#increase to 7gb
node --max-old-space-size=7168 index.js

#increase to 8gb 
node --max-old-space-size=8192 index.js 


i was struggling with this even after setting --max-old-space-size.

Then i realised need to put options --max-old-space-size before the karma script.

also best to specify both syntaxes --max-old-space-size and --max_old_space_size my script for karma :

node --max-old-space-size=8192 --optimize-for-size --max-executable-size=8192  --max_old_space_size=8192 --optimize_for_size --max_executable_size=8192 node_modules/karma/bin/karma start --single-run --max_new_space_size=8192   --prod --aot