TkbmCONNPOOL v. 0.98 (22. Jun 1999)
=========================================================================
A database connection pooling package.

BEFORE USING THIS COMPONENT, YOU ARE REQUESTED TO READ ALL OF THIS TEXT
DOCUMENT AND SPECIALLY TO NOTICE AND ACCEPT THE DISCLAIMER.

Can be used as a demonstration of how to create descendents of TDataSet,
or as in my case, to allow a program to generate temporary data that can
be used directly by all data aware controls.

Copyright 1999 Kim Bo Madsen/Optical Services - Scandinavia
All rights reserved.

You are allowed to used this component in any project for free.
You are NOT allowed to claim that you have created this component or to
copy its code into your own component and claim that is was your idea.

Im offering this for free for your convinience, and the ONLY thing I DEMAND
is to get an E-MAIL about what project this component (or dirived versions)
is used for. That will be my reward of offering this component for free to you!

You dont need to state my name in your software, although it would be
appreciated if you do.

If you find bugs or alter the component (f.ex. see suggested enhancements
further down), please DONT just send the corrected/new code out on the internet,
but instead send it to me, so I can put it into the official version. You will
be acredited if you do so.

Usage
=====

The components are heavily based on TkbmMemTable and thus that component MUST
exist to be able to install the TkbmConnPool package.

- Put a TDatabase on a datamodule. It will only be used as a template for
   internal database components.
- Put a TSession on the datamodule (if you require threaded operation) and
   set its AutoSessionName to true.
- Put a TkbmConnectionPool on the datamodule and set the Database property to
   point at the TDatabase you previously added. Set the max. number of
   simultanious connections to the database. There can be more than
   one TkbmConnectionPool on a form for different databases. The
   TkbmConnectionPool pool queries and queue them in an intelligent
   way. The seemingly fastest and shortest queue is allways used for
   a new query.
- Put a TkbmPooledSession on the datamodule Connect it to the TkbmConnectionPool.
   It handles multisession (multithreaded) environments.
- Create a new datamodule which will be cloned every time a new thread (web session)
   is started.
- Now put as many TkbmPooledQuery or TkbmPooledStoredProc as you need on
   the session datamodule and connect them to the TkbmPooledSession component.
   Optionally set the Sync property to either Async or Sync. If set to Sync, the
   queries/sproc will be executed in the queues in the order that they were executed
   in the application. If set to Async, they will be executed as fast as possible
   even in parallel.
   Beware that the components are READONLY. If you want to modify a record, you
   have to do it with SQL UPDATE commands. You ofcourse can use the
   TkbmPooledQuery for that purpose.

Components
==========

TkbmConnectionPool
------------------
Properties:

 MaxConnections (R/W, Integer) Max. number of concurrent database connections
                               shared among all users and queries.

 CurConnections (R, Integer)   Returns current number of established database
                               connections.

 CurConnectionsOwnerIDs (R, string)
                               Returns the owner ID's as a string of the currently
                               active connections.

 CurRequests (R, Integer)      Returns current number of queued requests.

 Database (R/W, TDatabase)     The database that is to be used as a template
                               for new database connections.

 MaxCacheAge (R/W, integer)    How old in secs. can a cached entry be before its discarded.

 MaxCacheEntries (R/W, integer)
                               How many entries can be cached before the least used will
                               be discarded.

 EnableCache (R/W, boolean)    Do caching or not.

 ConnectionTimeout (R/W, integer)
                               How many secs. will a connection to the database
                               be held after the last use before it is closed.

 GarbageInterval (R/W, integer)
                               How many secs between each garbage collection.

 GarbageCollection (R/W, boolean)
                               Will garbage collection happen? Garbage collection
                               takes care of removing timedout cached entries and
                               connections.

 CacheHits (R, longint)        Number of cache hits.
 CacheMisses (R,longint)       Number of cache misses.

Events:
 OnGetLogonParams(DBTemplate:TDatabase; ConnID:integer; var dbParams:TStringList)
                               Called whenever a new database connection is to be
                               made. ConnID is the number of the new connection (<MaxConnections).
                               dbParams contains the parameters (f.ex. user name/password etc) to
                               be used in creating a new database connection.

 OnGarbageCollection (R/W, TkbmConnectionPoolGarbageCollection)
                               Called each time a garbage collection is starting.

Methods:
 TimeoutConnections;           Mark all connections to be timed out.
 KillConnections;              Kill all connections as fast as possible.



TkbmPooledSession
-----------------
Properties:

  ConnectionPool (R/W, TkbmConnectionPool) The connectionpool to connect to.

  AutoSessionName (R/W, boolean) If to generate sessionnames automatically.
                                 Should be true for multithreaded applications.

  SessionName (R/W, string)      The logical name of this session (can be any string).
                                 If AutoSessionName=true then SessionName will be
                                 modified to always being unique.

  ThreadSessionName (R, string)  The unique version of SessionName if AutoSessionName=true.

  OwnerID (R/W, integer)         A number identifying the current user of this session.
                                 Can be used to track who is doing what.

  IsLocked (R, boolean)          Returns true if this session is locked for sync. use.

  SessionNumber (R/W, integer)   A user defined number. Not used by the system.

Methods:
  function LockSession(Sync:boolean):TkbmConnection
                                 Returns a connection object. If sync=true, locks the session
                                 for synchrone use only.
  procedure UnlockSession;       Unlocks the session object.

TkbmPooledDataSet
-----------------
  The ancestor of all pooled datasets. Inherits from TkbmMemTable which inherits from TDataset.

Properties:

  Sync (R/W, TkbmPooledSync)     Either kpssAsync or kpssSync.
  SessionName (R/W, string)      Refers to the SessionName of a TkbmPooledSession.
  CacheHits (R, longint)         Number of hits in the cache for this dataset.
  CacheMisses (R, longint)       Number of misses in the cache for this dataset.
  Cached (R/W, boolean)          Cache the contents of this dataset?
  CacheParams (R/W, TParamType)  Also cache the parameters (in/out) of this dataset?
  IsFromCache (R,boolean)        Returns true if the answer for the request came from the cache.
  MaxCacheRecordCount (R/W,integer)
                                 Dont cache datasets with more than this number of rows.

TkbmPooledQuery
---------------
  Inherits from TkbmPooledDataSet.
  Has the same functionality as TQuery + TkbmPooledDataSet + TkbmMemTable.

TkbmPooledStoredProc
--------------------
  Inherits from TkbmPooledDataSet.
  Has the same functionality as TStoredProc + TkbmPooledDataSet + TkbmMemTable.

Please see the comments in the start of the componentsource for whats new
in this release.

DISCLAIMER
By using this component or parts theiroff you are accepting the full
responsibility of the use. You are understanding that the author cant be
made responsible in any way for any problems occuring using this component.
You also recognize the author as the creator of this component and agrees
not to claim otherwize!

Please forward corrected versions (source code ONLY!), comments,
and emails saying you are using it for this or that project to:
          [email protected]
//=============================================================================

History:
  Please look in the sourcecode.

Contributors:

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