Multiple pipelines and limiting the number of connections.

Introducing a number of options to the multi interface that
allows for multiple pipelines to the same host, in order to
optimize the balance between the penalty for opening new
connections and the potential pipelining latency.

Two new options for limiting the number of connections:

CURLMOPT_MAX_HOST_CONNECTIONS - Limits the number of running connections
to the same host. When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished, so we can reuse the connection.

CURLMOPT_MAX_TOTAL_CONNECTIONS - Limits the number of connections in total.
When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished. The free connection will then be reused, if possible, or
closed if the pending handle can't reuse it.

Several new options for pipelining:

CURLMOPT_MAX_PIPELINE_LENGTH - Limits the pipeling length. If a
pipeline is "full" when a connection is to be reused, a new connection
will be opened if the CURLMOPT_MAX_xxx_CONNECTIONS limits allow it.
If not, the handle will be put in a pending state until a connection is
ready (either free or a pipe got shorter).

CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a transfer with a content
length that is larger than this.

CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a chunk larger than this.

CURLMOPT_PIPELINING_SITE_BL - A blacklist of hosts that don't allow
pipelining.

CURLMOPT_PIPELINING_SERVER_BL - A blacklist of server types that don't allow
pipelining.

See the curl_multi_setopt() man page for details.

1 files changed, 0 insertions, 7 deletions

diff --git a/lib/README.pipelining b/lib/README.pipelining
index c7b462248..e5bf6ec33 100644
--- a/lib/README.pipelining
+++ b/lib/README.pipelining
@@ -42,10 +42,3 @@ Details
   still resolve the second one properly to make sure that they actually _can_
   be considered for pipelining. Also, asking for explicit pipelining on handle
   X may be tricky when handle X get a closed connection.
-
-- We need options to control max pipeline length, and probably how to behave
-  if we reach that limit. As was discussed on the list, it can probably be
-  made very complicated, so perhaps we can think of a way to pass all
-  variables involved to a callback and let the application decide how to act
-  in specific situations. Either way, these fancy options are only interesting
-  to work on when everything is working and we have working apps to test with.