heapdump-analyser dump.heapsnapshotEnters interactive mode.
heapdump-analyser dump.heapsnapshot ClassToFind
heapdump-analyser dump.heapsnapshot ClosureToFind()
heapdump-analyser dump.heapsnapshot @IdToFindFinds all ClassToFind classes or ClosureToFind closures in the heapsnapshot and prints out a colorful retainer trace for them.
heapdump-analyser a.heapsnapshot b.heapsnapshot c.heapsnapshot [ClassToFind|ClosureToFind()|@IdToFind]Finds only retained objects in c.heapsnapshot that were allocated between a.heapsnapshot and b.heapsnapshot.
Compared to the v8 devtools it
- correctly analyses WeakMaps and circular dependencies within them.
- eliminates references between the classes/closures you are looking for.
Note that it may take a large amount of memory for the analysis so you may want to increase the max memory with NODE_OPTIONS=--max_old_space_size=16000. It takes about 16x size of heapsnapshot.
Note that creating a heapsnapshot is pretty slow and blocks execution of your code.
Since Node.js 16 you can use --heapsnapshot-near-heap-limit=1 to create a heapsnapshot when the process runs out of memory. Best reduce the available amount of memory via --max_old_space_size=500 to make it run out of memory faster and make the size of the heapsnapshot smaller.
node --max_old_space_size=500 --heapsnapshot-near-heap-limit=1 program.jsIt also possible to create a heapsnapshot on a signal via --heapsnapshot-signal=SIGUSR2
node --heapsnapshot-signal=SIGUSR2 program.js
ps aux
kill -USR2 1234The npm package heapdump allows to create a heapsnapshot from javascript:
console.log("creating heapdump...");
require("heapdump").writeSnapshot((err) => console.log("done", err));Using the devtools is not recommended since the devtools affect the results, are very slow and crash when the heapsnapshot is too large.