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, 366 insertions, 0 deletions

diff --git a/lib/pipeline.c b/lib/pipeline.c
new file mode 100644
index 000000000..7abc35fd0
--- /dev/null
+++ b/lib/pipeline.c
@@ -0,0 +1,366 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2013, Linus Nielsen Feltzing, <linus@haxx.se>
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#include <curl/curl.h>
+
+#include "urldata.h"
+#include "url.h"
+#include "progress.h"
+#include "multiif.h"
+#include "pipeline.h"
+#include "sendf.h"
+#include "rawstr.h"
+#include "bundles.h"
+
+#include "curl_memory.h"
+/* The last #include file should be: */
+#include "memdebug.h"
+
+struct site_blacklist_entry {
+  char *hostname;
+  unsigned short port;
+};
+
+static void site_blacklist_llist_dtor(void *user, void *element)
+{
+  struct site_blacklist_entry *entry = element;
+  (void)user;
+
+  Curl_safefree(entry->hostname);
+  Curl_safefree(entry);
+}
+
+static void server_blacklist_llist_dtor(void *user, void *element)
+{
+  char *server_name = element;
+  (void)user;
+
+  Curl_safefree(server_name);
+}
+
+bool Curl_pipeline_penalized(struct SessionHandle *data,
+                             struct connectdata *conn)
+{
+  if(data) {
+    bool penalized = FALSE;
+    curl_off_t penalty_size =
+      Curl_multi_content_length_penalty_size(data->multi);
+    curl_off_t chunk_penalty_size =
+      Curl_multi_chunk_length_penalty_size(data->multi);
+    curl_off_t recv_size = -2; /* Make it easy to spot in the log */
+
+    /* Find the head of the recv pipe, if any */
+    if(conn->recv_pipe && conn->recv_pipe->head) {
+      struct SessionHandle *recv_handle = conn->recv_pipe->head->ptr;
+
+      recv_size = recv_handle->req.size;
+
+      if(penalty_size > 0 && recv_size > penalty_size)
+        penalized = TRUE;
+    }
+
+    if(chunk_penalty_size > 0 &&
+       (curl_off_t)conn->chunk.datasize > chunk_penalty_size)
+      penalized = TRUE;
+
+    infof(data, "Conn: %d (%p) Receive pipe weight: (%d/%d), penalized: %d\n",
+          conn->connection_id, conn, recv_size,
+          conn->chunk.datasize, penalized);
+    return penalized;
+  }
+  return FALSE;
+}
+
+/* Find the best connection in a bundle to use for the next request */
+struct connectdata *
+Curl_bundle_find_best(struct SessionHandle *data,
+                      struct connectbundle *cb_ptr)
+{
+  struct curl_llist_element *curr;
+  struct connectdata *conn;
+  struct connectdata *best_conn = NULL;
+  size_t pipe_len;
+  size_t best_pipe_len = 99;
+
+  (void)data;
+
+  curr = cb_ptr->conn_list->head;
+  while(curr) {
+    conn = curr->ptr;
+    pipe_len = conn->send_pipe->size + conn->recv_pipe->size;
+
+    if(!Curl_pipeline_penalized(conn->data, conn) &&
+       pipe_len < best_pipe_len) {
+      best_conn = conn;
+      best_pipe_len = pipe_len;
+    }
+    curr = curr->next;
+  }
+
+  /* If we haven't found a connection, i.e all pipelines are penalized
+     or full, just pick one. The request will then be queued in
+     Curl_add_handle_to_pipeline(). */
+  if(!best_conn) {
+    best_conn = cb_ptr->conn_list->head->ptr;
+  }
+  return best_conn;
+}
+
+CURLcode Curl_add_handle_to_pipeline(struct SessionHandle *handle,
+                                     struct connectdata *conn)
+{
+  struct curl_llist_element *sendhead = conn->send_pipe->head;
+  struct curl_llist *pipeline;
+  CURLcode rc;
+
+  pipeline = conn->send_pipe;
+
+  infof(conn->data, "Adding handle: conn: %p\n", conn);
+  infof(conn->data, "Adding handle: send: %d\n", conn->send_pipe->size);
+  infof(conn->data, "Adding handle: recv: %d\n", conn->recv_pipe->size);
+  rc = Curl_addHandleToPipeline(handle, pipeline);
+
+  if(pipeline == conn->send_pipe && sendhead != conn->send_pipe->head) {
+    /* this is a new one as head, expire it */
+    conn->writechannel_inuse = FALSE; /* not in use yet */
+#ifdef DEBUGBUILD
+    infof(conn->data, "%p is at send pipe head!\n",
+          conn->send_pipe->head->ptr);
+#endif
+    Curl_expire(conn->send_pipe->head->ptr, 1);
+  }
+
+  print_pipeline(conn);
+
+  return rc;
+}
+
+/* Move this transfer from the sending list to the receiving list.
+
+   Pay special attention to the new sending list "leader" as it needs to get
+   checked to update what sockets it acts on.
+
+*/
+void Curl_move_handle_from_send_to_recv_pipe(struct SessionHandle *handle,
+                                             struct connectdata *conn)
+{
+  struct curl_llist_element *curr;
+
+  curr = conn->send_pipe->head;
+  while(curr) {
+    if(curr->ptr == handle) {
+      Curl_llist_move(conn->send_pipe, curr,
+                      conn->recv_pipe, conn->recv_pipe->tail);
+
+      if(conn->send_pipe->head) {
+        /* Since there's a new easy handle at the start of the send pipeline,
+           set its timeout value to 1ms to make it trigger instantly */
+        conn->writechannel_inuse = FALSE; /* not used now */
+#ifdef DEBUGBUILD
+        infof(conn->data, "%p is at send pipe head B!\n",
+              conn->send_pipe->head->ptr);
+#endif
+        Curl_expire(conn->send_pipe->head->ptr, 1);
+      }
+
+      /* The receiver's list is not really interesting here since either this
+         handle is now first in the list and we'll deal with it soon, or
+         another handle is already first and thus is already taken care of */
+
+      break; /* we're done! */
+    }
+    curr = curr->next;
+  }
+}
+
+bool Curl_pipeline_site_blacklisted(struct SessionHandle *handle,
+                                    struct connectdata *conn)
+{
+  if(handle->multi) {
+    struct curl_llist *blacklist =
+      Curl_multi_pipelining_site_bl(handle->multi);
+
+    if(blacklist) {
+      struct curl_llist_element *curr;
+
+      curr = blacklist->head;
+      while(curr) {
+        struct site_blacklist_entry *site;
+
+        site = curr->ptr;
+        if(Curl_raw_equal(site->hostname, conn->host.name) &&
+           site->port == conn->remote_port) {
+          infof(handle, "Site %s:%d is pipeline blacklisted\n",
+                conn->host.name, conn->remote_port);
+          return TRUE;
+        }
+        curr = curr->next;
+      }
+    }
+  }
+  return FALSE;
+}
+
+CURLMcode Curl_pipeline_set_site_blacklist(char **sites,
+                                           struct curl_llist **list_ptr)
+{
+  struct curl_llist *old_list = *list_ptr;
+  struct curl_llist *new_list = NULL;
+
+  if(sites) {
+    new_list = Curl_llist_alloc((curl_llist_dtor) site_blacklist_llist_dtor);
+    if(!new_list)
+      return CURLM_OUT_OF_MEMORY;
+
+    /* Parse the URLs and populate the list */
+    while(*sites) {
+      char *hostname;
+      char *port;
+      struct site_blacklist_entry *entry;
+
+      entry = malloc(sizeof(struct site_blacklist_entry));
+
+      hostname = strdup(*sites);
+      if(!hostname)
+        return CURLM_OUT_OF_MEMORY;
+
+      port = strchr(hostname, ':');
+      if(port) {
+        *port = '\0';
+        port++;
+        entry->port = (unsigned short)strtol(port, NULL, 10);
+      }
+      else {
+        /* Default port number for HTTP */
+        entry->port = 80;
+      }
+
+      entry->hostname = hostname;
+
+      if(!Curl_llist_insert_next(new_list, new_list->tail, entry))
+        return CURLM_OUT_OF_MEMORY;
+
+      sites++;
+    }
+  }
+
+  /* Free the old list */
+  if(old_list) {
+    Curl_llist_destroy(old_list, NULL);
+  }
+
+  /* This might be NULL if sites == NULL, i.e the blacklist is cleared */
+  *list_ptr = new_list;
+
+  return CURLM_OK;
+}
+
+bool Curl_pipeline_server_blacklisted(struct SessionHandle *handle,
+                                      char *server_name)
+{
+  if(handle->multi) {
+    struct curl_llist *blacklist =
+      Curl_multi_pipelining_server_bl(handle->multi);
+
+    if(blacklist) {
+      struct curl_llist_element *curr;
+
+      curr = blacklist->head;
+      while(curr) {
+        char *bl_server_name;
+
+        bl_server_name = curr->ptr;
+        if(Curl_raw_nequal(bl_server_name, server_name,
+                           strlen(bl_server_name))) {
+          infof(handle, "Server %s is blacklisted\n", server_name);
+          return TRUE;
+        }
+        curr = curr->next;
+      }
+    }
+
+    infof(handle, "Server %s is not blacklisted\n", server_name);
+  }
+  return FALSE;
+}
+
+CURLMcode Curl_pipeline_set_server_blacklist(char **servers,
+                                             struct curl_llist **list_ptr)
+{
+  struct curl_llist *old_list = *list_ptr;
+  struct curl_llist *new_list = NULL;
+
+  if(servers) {
+    new_list = Curl_llist_alloc((curl_llist_dtor) server_blacklist_llist_dtor);
+    if(!new_list)
+      return CURLM_OUT_OF_MEMORY;
+
+    /* Parse the URLs and populate the list */
+    while(*servers) {
+      char *server_name;
+
+      server_name = strdup(*servers);
+      if(!server_name)
+        return CURLM_OUT_OF_MEMORY;
+
+      if(!Curl_llist_insert_next(new_list, new_list->tail, server_name))
+        return CURLM_OUT_OF_MEMORY;
+
+      servers++;
+    }
+  }
+
+  /* Free the old list */
+  if(old_list) {
+    Curl_llist_destroy(old_list, NULL);
+  }
+
+  /* This might be NULL if sites == NULL, i.e the blacklist is cleared */
+  *list_ptr = new_list;
+
+  return CURLM_OK;
+}
+
+
+void print_pipeline(struct connectdata *conn)
+{
+  struct curl_llist_element *curr;
+  struct connectbundle *cb_ptr;
+  struct SessionHandle *data = conn->data;
+
+  cb_ptr = conn->bundle;
+
+  if(cb_ptr) {
+    curr = cb_ptr->conn_list->head;
+    while(curr) {
+      conn = curr->ptr;
+      infof(data, "- Conn %d (%p) send_pipe: %d, recv_pipe: %d\n",
+            conn->connection_id,
+            conn,
+            conn->send_pipe->size,
+            conn->recv_pipe->size);
+      curr = curr->next;
+    }
+  }
+}