Hi,I am using libevent to implement a HTTP server. I am observing a crash & connection disconnect in libevent in the following scenario.1. The process starts a libevent HTTP server & registers for callbacks for different URLs.2. For one of the GET request from the client, the server needs to keep the connection open & send chunk replies as when data from some other source arrive.3. So it does a *_reply_start() & then *_reply_chunk() when data is availableEverything works fine at the beginning , but after a while (random could in 30 mins or couple of hours) observe the following issues1. 1. The libevent crashes. Checked the core dump analysis of multiple crashes & it points to the following code.a. 0x0042b0a8 in evbuffer_add_buffer (outbuf=0x4924b8, inbuf=0x496428) at buffer.c:7742. Sometimes the connection between server & client gets disconnected. When checked through wireshark, observed a FIN ACK coming from the HTTP server.Below is a simplified code snippet showcasing the implementation & use case.I would appreciate if someone could let know, if I am doing something wrong in the usage of the libevent APIs & what could be the cause of the crash.#define KEY_STRING "CHECK"
struct evhttp_request *req; //Structure holds the req, on which chunk reply is sentpthread_t SenderThread;bool startSend = false;void connectionClosed(struct evhttp_connection* evcon, void* key){printf("Connection closed by client");}
//****** Function to send some data every 5 secs************/
void sendChunk(struct evhttp_connection* evcon, void* key){int counter = 0;printf("Start sending data everyy 5 secs");while(1){
if(startSend) //startSend is set to true when client does a GET & SSEEvents_cb() is invoked{evbuffer *databuf = evbuffer_new();if (databuf != NULL){evbuffer_add(databuf,"event:remoteEvent\n",strlen("event:remoteEvent\n"));evbuffer_add_printf(databuf,"data:TestDATA%d\n",counter);evhttp_send_reply_chunk(req, databuf);evbuffer_free(databuf);counter++;if(10000 == counter)counter = 0;}sleep(5);}else{sleep(2); //Sleep for 2 secs & then check if the flag is set or not
}}}///******Callback when Client does a GET on URL "/SSEEvents"********void SSEEvents_cb(struct evhttp_request *aReq, void *key){if (EVHTTP_REQ_GET == aReq->type){const char * getUri = evhttp_request_get_uri(aReq);if( NULL == getUri ){evhttp_send_reply(aReq, 400, "Bad request", NULL); //Response back to client}req = (evhttp_request*) aReq;evhttp_request_own(aReq);evhttp_connection_set_closecb(evhttp_request_get_connection(aReq),&connectionClosed, KEY_STRING);evhttp_add_header(aReq->output_headers,"Content-Type","text/event-stream"); //Mandatoryevhttp_send_reply_start(aReq, 200, "OK"); ///Start the reply & then set the flag so that chunk reply can be sent every 5 secs// Set this flag to true so that the sender thread can start sending chunk datastartSend = true;}else{evhttp_send_reply(aReq, 501, " SET Not Implemented", NULL);}}int StartServer(char *aIPAddress, char *aPort){base = event_base_new();if (!base){printf("Couldn't create an event_base: So Exiting");return 1;}/* Create a new evhttp object to handle requests. */http = evhttp_new(base);if (!http){printf("Couldn't create evhttp: So Exiting....");return 1;}//Register for callback for any HTTP request for url "SSEEvents"evhttp_set_cb(http, "/SSEEvents", SSEEvents_cb, this);/* Now we tell the evhttp what port to listen on */uint16_t port = atoi(aPort);handle = evhttp_bind_socket_with_handle(http, aIPAddress, port);if (!handle){printf("couldn't bind to IP & port %d. Exiting.",(uint16_t)port);return -1;}///** Launch Thread to send chunk reply after http client makes requestpthread_attr_t attr;pthread_attr_init(&attr);pthread_attr_setstacksize(&attr, (128 * 1024)); //128kbsint threadCreate = -1;threadCreate = pthread_create(&SenderThread, NULL, &sendChunk, NULL);event_base_dispatch(base);return 0;}int main(int argc , char *argv[]){StartServer(argv[1], argv[2]);}Regards,Alap