Tribblix: manual page: CURLMOPT_MAX_TOTAL

CURLMOPT_MAX_TOTAL_CONNECTIONS(3) Introduction to Library Functions

NAME

CURLMOPT_MAX_TOTAL_CONNECTIONS - max simultaneously open connections

SYNOPSIS

#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_MAX_TOTAL_CONNECTIONS,
long amount);

DESCRIPTION

Pass a long for the amount. The set number is used as the maximum
number of simultaneously open connections in total using this multi
handle. For each new session, libcurl might open a new connection up
to the limit set by CURLMOPT_MAX_TOTAL_CONNECTIONS(3). If
CURLMOPT_PIPELINING(3) is enabled, libcurl can try multiplexing if
the host is capable of it.

When more transfers are added to the multi handle than what can be
performed due to the set limit, they get queued up waiting for their
chance.

While a transfer is queued up internally waiting for a connection,
the CURLOPT_TIMEOUT_MS(3) timeout is counted inclusive of the waiting
time, meaning that if you set a too narrow timeout the transfer might
never even start before it times out. The
CURLOPT_CONNECTTIMEOUT_MS(3) time is also similarly still treated as
a per-connect timeout and might expire even before making a new
connection is permitted.

Changing this value while there are transfers in progress is
possible. The new value is then used the next time checks are
performed. Lowering the value does not close down any active
transfers, it simply does not allow new ones to get made.

DEFAULT

0, which means that there is no limit. It is then simply controlled
by the number of easy handles added concurrently and how much
multiplexing is being done.

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURLM *m = curl_multi_init();
/* never do more than 15 connections */
curl_multi_setopt(m, CURLMOPT_MAX_TOTAL_CONNECTIONS, 15L);
}

AVAILABILITY

Added in curl 7.30.0

RETURN VALUE

curl_multi_setopt(3) returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).