uWebSockets: Memory doesn't free

Hi I am running a simple test with the following code:

#include <iostream>

#include "App.h"

using namespace std;

struct SocketContext {
  string id;
};

int main(int argc, char** argv) {
  uWS::SSLApp({
    .key_file_name = getenv("SSL_KEY_FILE"),
    .cert_file_name = getenv("SSL_CERT_FILE")
  })
  .ws<SocketContext>(
    "/",
    {
      .compression = uWS::SHARED_COMPRESSOR,
      .maxPayloadLength = 256 * 1024,
      .idleTimeout = 60,
      .maxBackpressure = 64 * 1024,
      .closeOnBackpressureLimit = false,
      .resetIdleTimeoutOnSend = false,
      .sendPingsAutomatically = false,
      .upgrade = nullptr,
      .open = [](auto* ws) { },
      .message = [](auto* ws, string_view message, uWS::OpCode opCode) {  },
      .drain = [](auto* ws) { },
      .ping = [](auto* ws, string_view message) {},
      .pong = [](auto* ws, string_view message) {},
      .subscription = [](auto* ws, string_view message, int, int) {},
      .close = [](auto* ws, int code, string_view message) { }})
  .listen(8081,[](auto* token) {})
  .run();

  return 0;
}

uWebsocket version/commit used: https://github.com/uNetworking/uWebSockets/tree/ba6ff7b7f4015859586691c7c1ec0149a3ee3858 .

I run the process under massif memory tool valgrind --tool=massif --threshold=0.01 <executable>, and run a simple tester against this opening 100s of connections and terminating them.

This is the memory usage I get from massif:

    MB
59.74^                                  #                                     
     |                             @@::@#                                     
     |                             @ : @#:::@:::@:::@::::@::::::::@::: ::  :  
     |                             @ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                          :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                        :::@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                       :: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                   :@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                   :@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |                  ::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |              ::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |              ::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |            ::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |            ::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |         :::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |        ::::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |        ::::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |      ::::::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |  :@::::::::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
     |  :@::::::::::::::::@:::: :@:@ : @#:::@:::@:::@: ::@::::::::@:::::::@:::
   0 +----------------------------------------------------------------------->Gi
     0                                                                   23.00

Number of snapshots: 75
 Detailed snapshots: [3, 20, 27, 29, 32, 33 (peak), 37, 41, 45, 50, 60, 70]

The alignment might look a bit janky but point is that the memory doesn’t get released upon termination of the tester connections.

This is a problem I am dealing with at the moment in a production application, but for simplicity I wrote the code above. results are similar.

I did the same without use of SSL ( uWS::App()) and here is massif memory print:

     MB
4.821^                                       :                                
     |                                    :@#:::::::::::::::::::::::::::::::::
     |                                  :::@#::                              :
     |                                @@:::@#::                              :
     |                              :@@@:::@#::                              :
     |                           :@@:@@@:::@#::                              :
     |                         @@:@@:@@@:::@#::                              :
     |                      :::@@:@@:@@@:::@#::                              :
     |                    :@:::@@:@@:@@@:::@#::                              :
     |                  @::@:::@@:@@:@@@:::@#::                              :
     |                @@@::@:::@@:@@:@@@:::@#::                              :
     |              @:@@@::@:::@@:@@:@@@:::@#::                              :
     |           @:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |         :@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |        ::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |      @:::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |    ::@:::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |    ::@:::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |    ::@:::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
     |    ::@:::@@:@@:@@@::@:::@@:@@:@@@:::@#::                              :
   0 +----------------------------------------------------------------------->Mi
     0                                                                   281.8

Number of snapshots: 56
 Detailed snapshots: [7, 13, 15, 17, 18, 21, 22, 23, 27, 32, 34, 36, 37, 38, 40, 41, 42, 43, 48, 50, 52 (peak)]

Would appreciate any insights. Can provide any more information required.