Hi,

I am using CURLOPT_OPENSOCKETFUNCTION and CURLOPT_CLOSESOCKETFUNCTION callbacks to control the number of maximum connections allowed to use.

In my code, for each easy handle, I set these two callbacks as below.

    curl_easy_setopt(m_curl, CURLOPT_OPENSOCKETFUNCTION, doOpenSocket);
    curl_easy_setopt(m_curl, CURLOPT_OPENSOCKETDATA, this);
    curl_easy_setopt(m_curl, CURLOPT_CLOSESOCKETFUNCTION, doCloseSocket);
    curl_easy_setopt(m_curl, CURLOPT_CLOSESOCKETDATA, this);

In the OPENSOCKETFUNCTION callback, if maximum sockets are already opened, it queues this request up and return CURL_SOCKET_BAD.

curl_socket_t HttpClientTransfer::doOpenSocket(void* userp, curlsocktype purpose, struct curl_sockaddr* addr)
{
...

    if (m_connectionsInUse >= getMaxConnections())
    {
        m_queue.push_back(tr);
        tr->setQueued(true);

        hcmWarn("Maximum sockets reached, request queued up (%d in queue) [worker %p]\n", m_queue.size(), this);

        return CURL_SOCKET_BAD;
    }

    curl_socket_t sd = socket(addr->family, addr->socktype, addr->protocol);
    if (sd >= 0)
    {
        ++m_connectionsInUse;

        hcmInfo("Open socket %d (%d in use now) [worker %p]\n", sd, m_connectionsInUse, this);
        return sd;
    }
    else
    {
        hcmError("socket(): %s [worker %p]\n", strerror(errno), this);
        return CURL_SOCKET_BAD;
    }

}

int HttpClientTransfer::doCloseSocket(void* userp, curl_socket_t sd)
{
...

    if (sd >= 0)
    {
        close(sd);
        --m_connectionsInUse;

        hcmInfo("Close socket %d (%d remain in use) [worker %p]\n", sd, m_connectionsInUse, this);
        return 0;
    }
    else
    {
        hcmError("Invalid socket %d to close [worker %p]\n", sd, this);
        return 1;
    }
}

The problem I run into is the number of OPENSOCKET being called isn't equal to that of CLOSESOCKET, so we sometimes saw a situation that m_connectionsInUse becomes minus (shown in log as below).

<07:35:48.453 INF HCM 11686:11799 7:0>[closeSocket(HttpClientWorker.cpp:125)] Close socket 80 (-22 remain in use) [worker 0x1946ed0]

Any problem of the way that I'm using these two callbacks?

thanks,
yamin

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Received on 2012-01-04