1 ;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10 -*-
2 ;;;; *************************************************************************
3 ;;;; FILE IDENTIFICATION
6 ;;;; Purpose: Support function for connection pool
7 ;;;; Programmers: Kevin M. Rosenberg, Marc Battyani
8 ;;;; Date Started: Apr 2002
10 ;;;; This file, part of CLSQL, is Copyright (c) 2002-2010 by Kevin M. Rosenberg
12 ;;;; CLSQL users are granted the rights to distribute and use this software
13 ;;;; as governed by the terms of the Lisp Lesser GNU Public License
14 ;;;; (http://opensource.franz.com/preamble.html), also known as the LLGPL.
15 ;;;; *************************************************************************
17 (in-package #:clsql-sys)
19 (defparameter *db-pool-max-free-connections* 4
20 "Threshold of free-connections in the pool before we disconnect a database
21 rather than returning it to the pool. NIL for no limit. This is really a
22 heuristic that should, on avg keep the free connections about this size.")
24 (defvar *db-pool* (make-hash-table :test #'equal))
25 (defvar *db-pool-lock* (make-process-lock "DB Pool lock"))
27 (defclass conn-pool ()
28 ((connection-spec :accessor connection-spec :initarg :connection-spec)
29 (database-type :accessor pool-database-type :initarg :pool-database-type)
30 (free-connections :accessor free-connections :initform nil)
31 (all-connections :accessor all-connections :initform nil)
32 (lock :accessor conn-pool-lock
33 :initform (make-process-lock "Connection pool"))))
38 (defun acquire-from-pool (connection-spec database-type &optional pool encoding)
39 "Try to find a working database connection in the pool or create a new
40 one if needed. This performs 1 query against the DB to ensure it's still
41 valid. When possible (postgres, mssql) that query will be a reset
42 command to put the connection back into its default state."
43 (unless (typep pool 'conn-pool)
44 (setf pool (find-or-create-connection-pool connection-spec database-type)))
46 (loop for pconn = (with-process-lock ((conn-pool-lock pool) "Acquire")
47 (pop (free-connections pool)))
50 ;; test if connection still valid.
51 ;; (e.g. db reboot -> invalid connection )
53 (progn (database-acquire-from-conn-pool pconn)
55 (sql-database-error (e)
56 ;; we could check for a specific error,
57 ;; but, it's safer just to disconnect the pooled conn for any error ?
58 (warn "Database connection ~S had an error while acquiring from the pool:
62 ;;run database disconnect to give chance for cleanup
63 ;;there, then remove it from the lists of connected
65 (%pool-force-disconnect pconn)
66 (with-process-lock ((conn-pool-lock pool) "remove dead conn")
67 (setf (all-connections pool)
68 (delete pconn (all-connections pool))))
70 (let ((conn (connect (connection-spec pool)
71 :database-type (pool-database-type pool)
75 (setf (conn-pool conn) pool)
76 (with-process-lock ((conn-pool-lock pool) "new conection")
77 (push conn (all-connections pool)))
80 (defun release-to-pool (database &optional (pool (conn-pool database)))
81 "Release a database connection to the pool. The backend will have a
82 chance to do cleanup."
83 (unless (conn-pool database) (setf (conn-pool database) pool))
85 ;;We read the list of free-connections outside the lock. This
86 ;;should be fine as long as that list is never dealt with
87 ;;destructively (push and pop destructively modify the place,
88 ;;not the list). Multiple threads getting to this test at the
89 ;;same time might result in the free-connections getting
91 ((or (and *db-pool-max-free-connections*
92 (>= (length (free-connections pool))
93 *db-pool-max-free-connections*)))
94 (%pool-force-disconnect database)
96 (with-process-lock ((conn-pool-lock pool) "Remove extra Conn")
97 (setf (all-connections pool)
98 (delete database (all-connections pool)))))
101 (database-release-to-conn-pool database)
102 (with-process-lock ((conn-pool-lock pool) "Release to pool")
103 (push database (free-connections pool))))))
105 (defmethod database-acquire-from-conn-pool (database)
106 (case (database-underlying-type database)
108 (database-execute-command "RESET ALL" database))
110 (database-query "SHOW ERRORS LIMIT 1" database nil nil))
112 ;; rpc escape sequence since this can't be called as a normal sp.
113 ;;http://msdn.microsoft.com/en-us/library/aa198358%28SQL.80%29.aspx
114 (database-execute-command "{rpc sp_reset_connection}" database))
116 (database-query "SELECT 1;" database '(integer) nil))))
118 (defmethod database-release-to-conn-pool (database)
119 (case (database-underlying-type database)
122 ;;http://www.postgresql.org/docs/current/static/sql-discard.html
123 ;;this was introduced relatively recently, wrap in ignore-errors
124 ;;so that it doesn't choke older versions.
125 (database-execute-command "DISCARD ALL" database)))))
127 (defun clear-conn-pool (pool)
128 "Be careful this function will disconnect connections without regard
129 to whether another thread is actively using them."
130 (with-process-lock ((conn-pool-lock pool) "Clear pool")
131 (mapc #'%pool-force-disconnect (all-connections pool))
132 (setf (all-connections pool) nil
133 (free-connections pool) nil))
136 (defun find-or-create-connection-pool (connection-spec database-type)
137 "Find connection pool in hash table, creates a new connection pool
139 (let ((key (list connection-spec database-type)))
140 (with-process-lock (*db-pool-lock* "Find-or-create connection")
141 (or (gethash key *db-pool*)
142 (setf (gethash key *db-pool*)
143 (make-instance 'conn-pool
144 :connection-spec connection-spec
145 :pool-database-type database-type))))))
147 (defun disconnect-pooled (&optional clear)
148 "Disconnects all connections in the pool. When clear, also deletes
150 (with-process-lock (*db-pool-lock* "Disconnect pooled")
152 #'(lambda (key conn-pool)
153 (declare (ignore key))
154 (clear-conn-pool conn-pool))
156 (when clear (clrhash *db-pool*)))
159 (defun %pool-force-disconnect (database)
160 "Force disconnection of a connection from the pool."
161 ;;so it isn't just returned to pool
162 (setf (conn-pool database) nil)
163 ;; disconnect may error if remote side closed connection
164 (ignore-errors (disconnect :database database)))
166 ;(defun pool-start-sql-recording (pool &key (types :command))
167 ; "Start all stream in the pool recording actions of TYPES"
168 ; (dolist (con (pool-connections pool))
169 ; (start-sql-recording :type types
170 ; :database (connection-database con))))
172 ;(defun pool-stop-sql-recording (pool &key (types :command))
173 ; "Start all stream in the pool recording actions of TYPES"
174 ; (dolist (con (pool-connections pool))
175 ; (stop-sql-recording :type types
176 ; :database (connection-database con))))
178 ;(defmacro with-database-connection (pool &body body)
179 ; `(let ((connection (obtain-connection ,pool))
182 ; (with-database ((connection-database connection))
183 ; (setq results (multiple-value-list (progn ,@body))))
184 ; (release-connection connection))
185 ; (values-list results)))