Add option idle_timeout

The main problem with current implementation of HTTP server is it's
cooperative scheduling. To control connections we need invent something
that will periodically checks open connections and close idles with
exceeded timeout. In proposed implementation we close idle connections
with exceeded idle_timeout in synchronous manner - before start
processing a new connection. In comparison to other solutions (like
running checking function in a separate fiber) closing connections
synchronously is much easier to implement and don't make module complex.

Fixes #137

README.md

@@ -134,6 +134,9 @@ httpd = require('http.server').new(host, port[, { options } ])
 * `keepalive_disable` - disables keep-alive connections with misbehaving
   clients. Parameter accept a map that contains a user agents with non-nil
   value. By default map is empty.
+* `idle_timeout` - maximum amount of time an idle (keep-alive) connection will
+  remain idle before closing. When the idle timeout is exceeded, HTTP server
+  closes the keepalive connection. Default value: 0 seconds (disabled).
 
   Example:
 

http/server.lua

@@ -3,6 +3,7 @@
 local lib = require('http.lib')
 
 local fio = require('fio')
+local fiber = require('fiber')
 local require = require
 local package = package
 local mime_types = require('http.mime_types')
@@ -15,6 +16,21 @@ local errno = require 'errno'
 
 local DETACHED = 101
 
+-- A table that maps fiber object to time when it was active last time.
+-- Using for tracking idle connections.
+local connections = {}
+
+local function close_idle_connections(connections)
+    -- FIXME: complexity is O(N) and it is bad
+    for fiber_obj, start_time in pairs(connections) do
+        if fiber.clock() - start_time >= self.options.idle_timeout then
+            log.info("Connection closed, idle_timeout was exceeded (fiber id %d)\n", fiber_obj:id())
+            fiber_obj:cancel()
+            connections[fiber_obj] = nil
+        end
+    end
+end
+
 local function errorf(fmt, ...)
     error(string.format(fmt, ...))
 end
@@ -757,6 +773,11 @@ local function process_client(self, s, peer)
     while true do
         local hdrs = ''
 
+        connections[fiber.id] = fiber.clock()
+        if self.options.idle_timeout > 0 then
+            close_idle_connections(connections)
+        end
+
         local is_eof = false
         while true do
             local chunk = s:read{
@@ -979,6 +1000,9 @@ local function httpd_stop(self)
         self.tcp_server:close()
         self.tcp_server = nil
     end
+
+    connections = {}
+
     return self
 end
 
@@ -1303,6 +1327,10 @@ local exports = {
         if type(options.keepalive_disable) ~= 'table' then
             error('Option keepalive_disable must be a table.')
         end
+        if options.idle_timeout ~= nil and
+           type(options.idle_timeout) ~= 'number' then
+            error('Option idle_timeout must be a number.')
+        end
 
         local default = {
             max_header_size     = 4096,
@@ -1317,6 +1345,7 @@ local exports = {
             log_errors          = true,
             display_errors      = false,
             keepalive_disable   = {},
+            idle_timeout        = 0, -- no timeout, option is disabled
         }
 
         local self = {

test/integration/http_server_options_test.lua

@@ -30,6 +30,11 @@ g.before_test('test_keepalive_disallowed', function()
     g.httpd:start()
 end)
 
+g.before_test('test_idle_timeout_default', function()
+    g.httpd = helpers.cfgserv()
+    g.httpd:start()
+end)
+
 g.after_each(function()
     helpers.teardown(g.httpd)
 end)
@@ -73,3 +78,8 @@ g.test_keepalive_change_in_runtime = function(g)
         ["Mozilla/4.0"] = true
     })
 end
+
+g.test_idle_timeout_default = function(g)
+    local httpd = g.httpd
+    t.assert_equals(httpd.options.idle_timeout, 0)
+end