Server crash when dashboard call with several thousand of entries

[llaske]

When the dashboard is run on a database with several thousand of entries, the graph not drawn and the server crash.

On the server side the error is:

<--- Last few GCs --->

[18304:0x3924b60]    41557 ms: Mark-sweep 1347.3 (1456.2) -> 1347.3 (1456.2) MB, 141.8 / 0.0 ms  (average mu = 0.069, current mu = 0.001) allocation failure scavenge might not succeed
[18304:0x3924b60]    41699 ms: Mark-sweep 1347.3 (1456.2) -> 1347.2 (1440.2) MB, 141.6 / 0.0 ms  (average mu = 0.035, current mu = 0.001) last resort GC in old space requested


<--- JS stacktrace --->

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

Security context: 0x0f0dfe69e6e9 <JSObject>
    0: builtin exit frame: stringify(this=0x0f0dfe691a21 <Object map = 0x33024b5042a9>,0x26881e0826f1 <undefined>,0x26881e0826f1 <undefined>,0x379283b16cd1 <JSArray[7640]>,0x0f0dfe691a21 <Object map = 0x33024b5042a9>)

    1: arguments adaptor frame: 1->3
    2: stringify(aka stringify) [0x1097c01e5cb9] [/home/lionel/src/olpc/sugarizer-server/node_modules/express/lib/response.js:~1114] [pc=0x2e0...

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
 1: 0x8fa050 node::Abort() [node]
 2: 0x8fa09c  [node]
 3: 0xb0020e v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [node]
 4: 0xb00444 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [node]
 5: 0xef4952  [node]
 6: 0xef4a58 v8::internal::Heap::CheckIneffectiveMarkCompact(unsigned long, double) [node]
 7: 0xf00b32 v8::internal::Heap::PerformGarbageCollection(v8::internal::GarbageCollector, v8::GCCallbackFlags) [node]
 8: 0xf01464 v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [node]
 9: 0xf02979 v8::internal::Heap::CollectAllAvailableGarbage(v8::internal::GarbageCollectionReason) [node]
10: 0xf0413e v8::internal::Heap::AllocateRawWithRetryOrFail(int, v8::internal::AllocationSpace, v8::internal::AllocationAlignment) [node]
11: 0xed3d1b v8::internal::Factory::NewRawTwoByteString(int, v8::internal::PretenureFlag) [node]
12: 0x1203f60 v8::internal::IncrementalStringBuilder::Extend() [node]
13: 0xfc8141 v8::internal::JsonStringifier::SerializeString(v8::internal::Handle<v8::internal::String>) [node]
14: 0xfc859b v8::internal::JsonStringifier::Result v8::internal::JsonStringifier::Serialize_<true>(v8::internal::Handle<v8::internal::Object>, bool, v8::internal::Handle<v8::internal::Object>) [node]
15: 0xfcd6ad v8::internal::JsonStringifier::Result v8::internal::JsonStringifier::Serialize_<false>(v8::internal::Handle<v8::internal::Object>, bool, v8::internal::Handle<v8::internal::Object>) [node]
16: 0xfcabfa v8::internal::JsonStringifier::Result v8::internal::JsonStringifier::Serialize_<true>(v8::internal::Handle<v8::internal::Object>, bool, v8::internal::Handle<v8::internal::Object>) [node]
17: 0xfcd6ad v8::internal::JsonStringifier::Result v8::internal::JsonStringifier::Serialize_<false>(v8::internal::Handle<v8::internal::Object>, bool, v8::internal::Handle<v8::internal::Object>) [node]
18: 0xfcd316 v8::internal::JsonStringifier::Result v8::internal::JsonStringifier::Serialize_<false>(v8::internal::Handle<v8::internal::Object>, bool, v8::internal::Handle<v8::internal::Object>) [node]
19: 0xfce409 v8::internal::JsonStringifier::Stringify(v8::internal::Handle<v8::internal::Object>, v8::internal::Handle<v8::internal::Object>, v8::internal::Handle<v8::internal::Object>) [node]
20: 0xbd4d31 v8::internal::Builtin_JsonStringify(int, v8::internal::Object**, v8::internal::Isolate*) [node]
21: 0x2e091c8dbf7d 
Abandon (core dumped)

[im-prakher]

@llaske due to such huge amount of data, the memory size must have exceeded its limit for the heap in v8. Have a look at this,
heap-size-limit in v8.

By the way, restarting the server with following command to increase the memory for process will solve the issue,
node --max-old-space-size="NEW_MEMORY_SIZE in MB" server.js

For 8GB memory space set memory size to 8192 MB,
node --max-old-space-size=8192 server.js

This will start the server.js with a memory limit of 8 GB.

[llaske]

@im-prakher thanks for the advice but increasing the memory will not solve the issue when users count will continue to grow.
We should found a more long-term solution.

[llaske]

Fixed in #212