Managed memory leak when calling from JS to .NET

[tjanczuk]

The following code generates a managed memory leak (managed heap ever increasing). Ultimately (~10min on my box) the process fails with out of memory exception:

var func = require('edge').func(function () {/*
    async (object input) => {
        return null;
    }
*/});

var data = '{"data_package_id":"341f0a51-3521-400e-ba05-b86939433e9b","timestamp":1375988508262,"records":[{"id":"df63580b-5047-4ed2-a5f3-e928abd8414a","timestamp":1375988508118,"context":[],"target_users":[],"extension":{"eventRecordTime":1375988508118,"apiVersion":"v1","shortUrl":"shortUrl","httpMethod":"POST","callerUserAgent":"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.110 Safari/537.36","azureDeployName":"localhost","connectionId":"3f813fd4-aea9-4e7b-a44c-e4a3f75da38b"},"sampling_data":{},"context_ids":{"connectionId":"1bb5c8d4-acc2-4a01-aa7e-79317eedd5d5"},"event_type":"edf_trouter_request_check","type":"trouter"}],"ids":{"deployment":"TrouterTest"},"schema":1,"type":"Service","source":"Node Test","version":"1.0.0.0"}';

function one() {
    func(data, function (error, data) {
        if (error) throw error;
        setTimeout(one, 1);
    });
}

one();

[tjanczuk]

Useful resource: http://www.codeproject.com/Articles/19490/Memory-Leak-Detection-in-NET

It appears the ClrFuncInvokeContext associated with a call from V8 to CLR is never collected, which also contains other objects in its closure:

!dumpheap -stat
...
03be0f14    77629      2173612 ClrFuncInvokeContext
64112b0c    77629      2484128 System.Action
6411acc0    78354    120662376 System.String

[tjanczuk]

Root cause: ClrFuncInvokeContext remained GC-rooted when CLR function completed synchronously on V8 thread. This prevented ClrFuncInvokeContext along with its closure (which includes payload passed from CLR to JS) from being reclaimed by the GC.

[tjanczuk]

The fix is to refactor code such the ClrFuncInvokeContext is being GC-rooted only when the CLR function does not complete synchronously.

[tjanczuk]

For future reference: here is a guide to native leak investigation with windbg: http://www.codeproject.com/Articles/31382/Memory-Leak-Detection-Using-Windbg