From 7ad59e0c48e12febae2a2fe86b76116c05977c6f Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Mon, 20 Dec 2010 00:14:52 +0000
Subject: http: support keepalive_requests directive

This limits the number of keepalive requests of a single
connection to prevent a single client from monopolizing server
resources.  On multi-process servers (e.g. Rainbows!) with many
keepalive clients per worker process, this can force a client to
reconnect and increase its chances of being accepted on a
less-busy worker process.

This directive is named after the nginx directive which
is identical in function.
---
 ext/unicorn_http/unicorn_http.rl | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

(limited to 'ext')

diff --git a/ext/unicorn_http/unicorn_http.rl b/ext/unicorn_http/unicorn_http.rl
index 42fcf1d..ba7ecb3 100644
--- a/ext/unicorn_http/unicorn_http.rl
+++ b/ext/unicorn_http/unicorn_http.rl
@@ -26,10 +26,34 @@
 /* all of these flags need to be set for keepalive to be supported */
 #define UH_FL_KEEPALIVE (UH_FL_KAVERSION | UH_FL_REQEOF | UH_FL_HASHEADER)
 
+static unsigned long keepalive_requests = 100; /* same as nginx */
+
+/*
+ * Returns the maximum number of keepalive requests a client may make
+ * before the parser refuses to continue.
+ */
+static VALUE ka_req(VALUE self)
+{
+  return ULONG2NUM(keepalive_requests);
+}
+
+/*
+ * Sets the maximum number of keepalive requests a client may make.
+ * A special value of +nil+ causes this to be the maximum value
+ * possible (this is architecture-dependent).
+ */
+static VALUE set_ka_req(VALUE self, VALUE val)
+{
+  keepalive_requests = NIL_P(val) ? ULONG_MAX : NUM2ULONG(val);
+
+  return ka_req(self);
+}
+
 /* keep this small for Rainbows! since every client has one */
 struct http_parser {
   int cs; /* Ragel internal state */
   unsigned int flags;
+  unsigned long nr_requests;
   size_t mark;
   size_t offset;
   union { /* these 2 fields don't nest */
@@ -465,6 +489,7 @@ static VALUE HttpParser_init(VALUE self)
   http_parser_init(hp);
   hp->buf = rb_str_new(NULL, 0);
   hp->env = rb_hash_new();
+  hp->nr_requests = keepalive_requests;
 
   return self;
 }
@@ -628,13 +653,15 @@ static VALUE HttpParser_keepalive(VALUE self)
  *    parser.next? => true or false
  *
  * Exactly like HttpParser#keepalive?, except it will reset the internal
- * parser state if it returns true.
+ * parser state on next parse if it returns true.  It will also respect
+ * the maximum *keepalive_requests* value and return false if that is
+ * reached.
  */
 static VALUE HttpParser_next(VALUE self)
 {
   struct http_parser *hp = data_get(self);
 
-  if (HP_FL_ALL(hp, KEEPALIVE)) {
+  if ((HP_FL_ALL(hp, KEEPALIVE)) && (hp->nr_requests-- != 0)) {
     http_parser_init(hp);
     hp->flags = UH_FL_TO_CLEAR;
     return Qtrue;
@@ -781,6 +808,13 @@ void Init_unicorn_http(void)
    */
   rb_define_const(cHttpParser, "LENGTH_MAX", OFFT2NUM(UH_OFF_T_MAX));
 
+  /* default value for keepalive_requests */
+  rb_define_const(cHttpParser, "KEEPALIVE_REQUESTS_DEFAULT",
+                  ULONG2NUM(keepalive_requests));
+
+  rb_define_singleton_method(cHttpParser, "keepalive_requests", ka_req, 0);
+  rb_define_singleton_method(cHttpParser, "keepalive_requests=", set_ka_req, 1);
+
   init_common_fields();
   SET_GLOBAL(g_http_host, "HOST");
   SET_GLOBAL(g_http_trailer, "TRAILER");
-- 
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