[Twisted-Python] Effects of backlog parameter on listenTCP
itamar at itamarst.org
Wed Jul 18 21:19:12 EDT 2012
On 07/18/2012 07:43 PM, Tobias Oberstein wrote:
> Could someone shortly elaborate on the semantics / effect of the parameter "backlog" with listenTCP?
> The docs say: "size of the listen queue".
> Is that a tunable within Twisted?
> I mean, there are kernel parameters for queue sizes of not yet completely TCP handshaked connections and so on. But those are kernel tunables.
> What does the "backlog" parameter?
> The reason I am asking: I am stress testing a Twisted server and I see client connections denied upon high connection rates .. does the parameter help?
It's the parameter passed to the listen(2) system call - from the man page:
The backlog argument defines the maximum length to which the
queue of pending connections for sockfd may grow. If a connection
request arrives when the
queue is full, the client may receive an error with an
indication of ECONNREFUSED or, if the underlying protocol supports
retransmission, the request may
be ignored so that a later reattempt at connection succeeds.
So, yes, higher values will prevent connection refused.
More information about the Twisted-Python