;;;; *************************************************************************
;;;; FILE IDENTIFICATION
;;;;
-;;;; Name: pool.cl
+;;;; Name: pool.lisp
;;;; Purpose: Support function for connection pool
;;;; Programmers: Kevin M. Rosenberg, Marc Battyani
;;;; Date Started: Apr 2002
;;;;
-;;;; $Id: pool.lisp,v 1.1 2002/09/30 10:19:23 kevin Exp $
-;;;;
-;;;; This file, part of CLSQL, is Copyright (c) 2002 by Kevin M. Rosenberg
+;;;; This file, part of CLSQL, is Copyright (c) 2002-2010 by Kevin M. Rosenberg
;;;;
;;;; CLSQL users are granted the rights to distribute and use this software
;;;; as governed by the terms of the Lisp Lesser GNU Public License
;;;; (http://opensource.franz.com/preamble.html), also known as the LLGPL.
;;;; *************************************************************************
-(declaim (optimize (debug 3) (speed 3) (safety 1) (compilation-speed 0)))
-(in-package :clsql-sys)
+(in-package #:clsql-sys)
+
+(defparameter *db-pool-max-free-connections* 4
+ "Threshold of free-connections in the pool before we disconnect a
+ database rather than returning it to the pool. This is really a heuristic
+that should, on avg keep the free connections about this size.")
(defvar *db-pool* (make-hash-table :test #'equal))
+(defvar *db-pool-lock* (make-process-lock "DB Pool lock"))
(defclass conn-pool ()
((connection-spec :accessor connection-spec :initarg :connection-spec)
- (database-type :accessor database-type :initarg :database-type)
- (free-connections :accessor free-connections
- :initform (make-array 5 :fill-pointer 0 :adjustable t))
- (all-connections :accessor all-connections
- :initform (make-array 5 :fill-pointer 0 :adjustable t))))
-
-(defun acquire-from-conn-pool (pool)
- (if (zerop (length (free-connections pool)))
- (let ((conn (connect (connection-spec pool)
- :database-type (database-type pool) :if-exists :new)))
- (vector-push-extend conn (all-connections pool))
- (setf (conn-pool conn) pool)
- conn)
- (vector-pop (free-connections pool))))
-
-(defun release-to-conn-pool (conn)
- (vector-push-extend conn (free-connections (conn-pool conn))))
+ (database-type :accessor pool-database-type :initarg :pool-database-type)
+ (free-connections :accessor free-connections :initform nil)
+ (all-connections :accessor all-connections :initform nil)
+ (lock :accessor conn-pool-lock
+ :initform (make-process-lock "Connection pool"))))
-(defun clear-conn-pool (pool)
- (loop for conn across (all-connections pool)
- do (setf (conn-pool conn) nil)
- (disconnect :database conn))
- (setf (fill-pointer (free-connections pool)) 0)
- (setf (fill-pointer (all-connections pool)) 0))
-(defun find-or-create-connection-pool (connection-spec database-type)
- "Find connection pool in hash table, creates a new connection pool if not found"
- (let* ((key (list connection-spec database-type))
- (conn-pool (gethash key *db-pool*)))
- (unless conn-pool
- (setq conn-pool (make-instance 'conn-pool
- :connection-spec connection-spec
- :database-type database-type))
- (setf (gethash key *db-pool*) conn-pool))
- conn-pool))
-
-(defun acquire-from-pool (connection-spec database-type &optional pool)
+(defun acquire-from-pool (connection-spec database-type &optional pool encoding)
+ "Try to find a working database connection in the pool or create a new
+one if needed. This performs 1 query against the DB to ensure it's still
+valid. When possible (postgres, mssql) that query will be a reset
+command to put the connection back into its default state."
(unless (typep pool 'conn-pool)
(setf pool (find-or-create-connection-pool connection-spec database-type)))
- (acquire-from-conn-pool pool))
+ (or
+ (loop for pconn = (with-process-lock ((conn-pool-lock pool) "Acquire")
+ (pop (free-connections pool)))
+ always pconn
+ thereis
+ ;; test if connection still valid.
+ ;; (e.g. db reboot -> invalid connection )
+ (handler-case
+ (progn (database-acquire-from-conn-pool pconn)
+ pconn)
+ (sql-database-error (e)
+ ;; we could check for a specific error,
+ ;; but, it's safer just to disconnect the pooled conn for any error ?
+ (warn "Database connection ~S had an error while acquiring from the pool:
+ ~S
+Disconnecting.~%"
+ pconn e)
+ ;;run database disconnect to give chance for cleanup
+ ;;there, then remove it from the lists of connected
+ ;;databases.
+ (%pool-force-disconnect pconn)
+ (with-process-lock ((conn-pool-lock pool) "remove dead conn")
+ (setf (all-connections pool)
+ (delete pconn (all-connections pool))))
+ nil)))
+ (let ((conn (connect (connection-spec pool)
+ :database-type (pool-database-type pool)
+ :if-exists :new
+ :make-default nil
+ :encoding encoding)))
+ (with-process-lock ((conn-pool-lock pool) "new conection")
+ (push conn (all-connections pool))
+ (setf (conn-pool conn) pool))
+ conn)))
(defun release-to-pool (database)
- (release-to-conn-pool database))
+ "Release a database connection to the pool. The backend will have a
+chance to do cleanup."
+ (let ((pool (conn-pool database)))
+ (cond
+ ;;We read the list of free-connections outside the lock. This
+ ;;should be fine as long as that list is never dealt with
+ ;;destructively (push and pop destructively modify the place,
+ ;;not the list). Multiple threads getting to this test at the
+ ;;same time might result in the free-connections getting
+ ;;longer... meh.
+ ((and *db-pool-max-free-connections*
+ (>= (length (free-connections pool))
+ *db-pool-max-free-connections*))
+ (%pool-force-disconnect database)
+ (with-process-lock ((conn-pool-lock pool) "Remove extra Conn")
+ (setf (all-connections pool)
+ (delete database (all-connections pool)))))
+ (t
+ ;;let it do cleanup
+ (database-release-to-conn-pool database)
+ (with-process-lock ((conn-pool-lock pool) "Release to pool")
+ (push database (free-connections pool)))))))
+
+(defmethod database-acquire-from-conn-pool (database)
+ (case (database-underlying-type database)
+ (:postgresql
+ (database-execute-command "RESET ALL" database))
+ (:mysql
+ (database-query "SHOW ERRORS LIMIT 1" database nil nil))
+ (:mssql
+ ;; rpc escape sequence since this can't be called as a normal sp.
+ ;;http://msdn.microsoft.com/en-us/library/aa198358%28SQL.80%29.aspx
+ (database-execute-command "{rpc sp_reset_connection}" database))
+ (T
+ (database-query "SELECT 1;" database '(integer) nil))))
+
+(defmethod database-release-to-conn-pool (database)
+ (case (database-underlying-type database)
+ (:postgresql
+ (ignore-errors
+ ;;http://www.postgresql.org/docs/current/static/sql-discard.html
+ ;;this was introduced relatively recently, wrap in ignore-errors
+ ;;so that it doesn't choke older versions.
+ (database-execute-command "DISCARD ALL" database)))))
+
+(defun clear-conn-pool (pool)
+ (with-process-lock ((conn-pool-lock pool) "Clear pool")
+ (mapc #'%pool-force-disconnect (all-connections pool))
+ (setf (all-connections pool) nil
+ (free-connections pool) nil))
+ nil)
+
+(defun find-or-create-connection-pool (connection-spec database-type)
+ "Find connection pool in hash table, creates a new connection pool
+if not found"
+ (with-process-lock (*db-pool-lock* "Find-or-create connection")
+ (let* ((key (list connection-spec database-type))
+ (conn-pool (gethash key *db-pool*)))
+ (unless conn-pool
+ (setq conn-pool (make-instance 'conn-pool
+ :connection-spec connection-spec
+ :pool-database-type database-type))
+ (setf (gethash key *db-pool*) conn-pool))
+ conn-pool)))
(defun disconnect-pooled (&optional clear)
- "Disconnects all connections in the pool"
- (maphash
- #'(lambda (key conn-pool)
- (declare (ignore key))
- (clear-conn-pool conn-pool))
- *db-pool*)
- (when clear (clrhash *db-pool*))
+ "Disconnects all connections in the pool. When clear, also deletes
+the pool objects."
+ (with-process-lock (*db-pool-lock* "Disconnect pooled")
+ (maphash
+ #'(lambda (key conn-pool)
+ (declare (ignore key))
+ (clear-conn-pool conn-pool))
+ *db-pool*)
+ (when clear (clrhash *db-pool*)))
t)
+(defun %pool-force-disconnect (database)
+ "Force disconnection of a connection from the pool."
+ ;;so it isn't just returned to pool
+ (setf (conn-pool database) nil)
+ ;; disconnect may error if remote side closed connection
+ (ignore-errors (disconnect :database database)))
+
+;(defun pool-start-sql-recording (pool &key (types :command))
+; "Start all stream in the pool recording actions of TYPES"
+; (dolist (con (pool-connections pool))
+; (start-sql-recording :type types
+; :database (connection-database con))))
+
+;(defun pool-stop-sql-recording (pool &key (types :command))
+; "Start all stream in the pool recording actions of TYPES"
+; (dolist (con (pool-connections pool))
+; (stop-sql-recording :type types
+; :database (connection-database con))))
+
+;(defmacro with-database-connection (pool &body body)
+; `(let ((connection (obtain-connection ,pool))
+; (results nil))
+; (unwind-protect
+; (with-database ((connection-database connection))
+; (setq results (multiple-value-list (progn ,@body))))
+; (release-connection connection))
+; (values-list results)))
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