US20060146877A1 - Multipool using automatically maintained active connection pool list - Google Patents

Abstract

Multipools can keep track of dead connection pools and can avoid selection of the dead connection pools. The multipool can check whether a connection pool has revived in the background.

Description

CLAIM OF PRIORITY
• This application claims priority to U.S. Provisional Application No. 60/640,449 entitled “Multipool Improvements” by Rahul Srivastava, filed Dec. 31, 2004 [Attorney Docket No. BEAS-01789US0].
BACKGROUND OF INVENTION
• Application servers, such as the WebLogic™ Server available from BEA Systems of San Jose, Calif., allow users to do a number of functions. One of the functions typically supported by application servers is to provide access to a database. In one embodiment, a connection pool such as a Java Database Connectivity (JDBC) connection pool is provided by the application server. The connection pool provides a number of already set up connections with a database. These connections are provided to applications of the application server as needed. Such connection pools allow for a relatively large number of applications in the application server to access a database while reducing the database connection time for the application.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a diagram illustrating the use of a multipool with a multipool manager of one embodiment.
• FIGS. 2A-2B are diagrams illustrating the use of a multipool manager having an active connection pool list.
• FIGS. 3A-3B are flowcharts that illustrate the use of an active connection pool list of one embodiment.
• FIG. 4 is a diagram illustrating the operation of a multipool manager of one embodiment of the present invention.
• FIGS. 5A-5B are diagrams that illustrate the use of callbacks with a multipool manager of embodiments of the present invention.
• FIG. 6 is a flowchart illustrating the use of callbacks with a multipool manager of one embodiment of the present invention.
DETAILED DESCRIPTIONMultipools using Automatically Maintained Active Connection Pool List
• FIG. 1 is a diagram that illustrates the operation of amultipool manager102. In some systems, it is desired to have multiple database instances, such asdatabase instances104 and106. Thedatabase instances104 and106 can each contain a current version of a database run on independent machines, for example. When there are multiple database instances, it can be desirable to use multiple connection pools, such asconnection pool108 andconnection pool110. Rather than dedicating each application, such asapplications112,114 and116, to a single connection pool and thus to a single database instance, a multipool system can be used. In a multipool system, amultipool manager102 can determine which connection pool to use to obtain a connection for an application into the database system.
• Diffferent methods for selecting a connection pool are possible. One selection method has a primary connection pool and a backup connection pool. The connections are first attempted at a primary connection pool and then upon failure event, the connections are then sent through a backup connection pool. Another method is a load balancing method where the connections are distributed between multiple connection pools to balance the load at the different connection pools. A round-robin method is an example of a load balancing method.
• One embodiment of the present invention comprises a multipool system to connect to database instances comprisingmultiple connection pools202 and204. The connection pools202 and204 are adapted to provide connections todatabase instances206 and208. Amultipool manager210 is adapted to select and set up connections to a database instance through a connection pool. Themultipool manager210 is adapted to keep track of dead connection pools between requests for conections.
• Themultipool manager210 can select a connection pool in a manner that avoids any dead connection pools. For the example ofFIG. 2A, the multipool manager can avoid selecting connection pool A if it is dead. In one embodiment, a selection of only non-dead connection pools is done as authorized by an application. In one embodiment, the application indicates by a callback or by configuration info whether to switch connection pools.
• Themultipool manager210 can be adapted to maintain alist212 of active connection pools and to use thelist212 to determine what connection pool to connect through. The term “list” is not meant to imply any specific data structure. The active connection pools on the list can include those connection pools that are not those connection pools determined by the multipool manager to be dead.
• Dead connection pools can be tested in the background to see whether they should be returned to the active connection pool list. The list of active connection pools can be a subset of a candidate list provided by an application. Alternatively, separate candidate lists and active lists can be maintained, and the multipool manager can select a connection pool that is on both lists. Themultipool manager210 can store an indication for each connection pool associated with the candidate list indicating whether the connnection pool is active or dead.
• In example ofFIG. 2A, the connection pool A is dead, thus not on the activeconnection pool list212. An application, such as anapplication220, can request a connection into one of thedatabase instances206 or208 through themultipool manager210. InFIG. 2A, themultipool manager210 selects a connection through the connection pool B.
• Themultipool manager210 can test whether a connection pool has been revived in the background asynchronously. In one embodiment, an asychronousbackground test module214 can be used.
• FIG. 2B illustrates an example of this background testing. In this example, a SQL test query is sent to the dead connection pool A. If the correct answer is obtained from thedatabase instance206, themultipool manager210 can update the activeconnection pool list212 with an indication of the connection pool A. In this way, the next time an application requests a connection to a database, a connection through the connection pool A is possible.
• FIG. 3B illustrates a flowchart illustrating the asynchronous testing of a dead connection pools. In one embodiment, preset wait time passes instep300. The wait time can be set by an application and stored with the configureation information for the multipool manager or a default value can be used Instep302, the dead connection pool is tested. If the dead connection pool has revived as indicated by the test, the activeconnection pool list306 is updated, otherwise, the cycle repeats waiting the preset time instep300.
• FIG. 3A illustrates the operation of the request for a connection to a database in one embodiment. Instep308, a request for connection to the database is received at a multipool manager. Instep310, the multipool manager can select a connection pool. In one embodiment, themultipool manager210 selects a connection pool on an active connection pool list. The connection can then be attemped. Instep312, it is checked whether the connection pool is dead. If the connection pool is dead, instep314, the active connection pool list is updated and new connection pool is selected from the active pool list. If the connection pool is not dead, instep315, it is checked to see whether the connection pool is full. If there is no available connections, then the multipool manager can select another connection pool from the active connection pool list, instep310. If any selected connection pool is not dead or full, then, instep316, the connection is done through the selected connection pool.
• FIG. 4 is a flowchart illustrating different conditions that can occur in one embodiment of the present invention. Instep402, a request for a connection to the database is received at a multipool manager. In step404 a multipool manager selects a connection pool from the active pool list. Its possible, as determined in step408, that the selected connection pool is a newly revived connection pool. If so, this is called a failback as indicated in step410. Instep412, it is checked whether the connection pool is dead. If a connection pool is dead, the active connection pool list is updated instep414, and instep416, another connection pool is selected from the active connection pool list, this is called a failover condition. Instep418, if the connection pool is not dead it is checked to see whether the connection pool is full. If the connection pool is full, instep420, it is checked to see whether a spillover is allowed. If it is, instep422 another connection pool is selected from the active connection pool list.Step424, shows a connection is made. As described below an application may authorize a failback, failover or spillover condition with a callback or with config information.
• One embodiment of the present invention is a multipool manager adapted to select and set up connections to a database instance through a connection pool. The multipool manager is adapted to keep track of dead connection pools. The multipool manager implements a selection method in which the multipool manager avoids selecting dead connection pools to provide a connection for an appplication.
• One embodiment of the present invention is a multipool system to connect to database instances comprising multiple connection pools. The connection pools are adapted to provide connections to database instances. A multipool manager is adapted to select and set up connections to a database instance through a connection pool. The multipool manager is adapted to keep track of dead connection pools and to asynchronously test whether a connection pool is revived.
Callback Interface for Multipools
• In some instances it is desirable to check with the application before switching the connection pool. Switching a connection pool can be a complicated process. Sometimes there are preferred database instances and it is not desired that the user switch to another less desirable database instance unless the first database instances are truly unavailable. In one embodiment of the present invention, the multipool manager implements callbacks to an application in order to get authorization from the application for a switch of connection pools.
• In one embodiment of the present invention, a multipool system is used to connect to database instances with multiple connection pools. The connection pools502 and504 are adapted to provide connections todatabase instances508 and510. Amultipool manager506 is adapted to select and set up connections to a database instance through a connection pool. Themultipool manager506 is adapted to check with anapplication512 before switching connection pools.
• In the example ofFIG. 5A, a callback is available from themultipool manager506 to theapplication512. If the connection pool is to be switched, themultipool manager506 can do a callback to theapplication512 to determine whether the application will authorize the switch. In example ofFIG. 5A, the active connection pool list includes connection pool B but not connection pool A. Before switching to connection pool B themultipool pool manager506 can do a callback to theapplication512. In one embodiment, in step 1 a request for connection is received by themultipool manager506. Instep 2, after the multipool manager determines that a connection pool switch may be desirable, a callback is done to theapplication512. The callback can be, for example, the calling of thecallback method514 which is part of theapplication512. Themultipool manager506 can storeconfiguration information506awhich may include an indication of what conditions the callback is to be sent and/or an indication of the callback method name, in this case, callback method A. The application code can implement acallback method514 in any manner. In one embodiment, a callback response is received by the multipool manager instep 3. The callback response can be an indication whichmultipool manager506 can use to determine how to connect.
• In one embodiment, the callback response indications include an “OK” indication. When the “OK” indication is received, the multipool manager switches to the new connection pool. Another callback response indication is a “retry” indication. If a “retry” indication is received, themultipool manager506 can attempt to get a connection with the old connection pool. Another possible callback response indication is a “don't reconnect” indication. When a “don't reconnect” indication is received the multipool manager not attempt to make a connection.
• FIG. 5B illustrates a possible reason that a “retry” indication might be provided by the callback method. In one example, it may be desirable to do a certain number of attempts onto a primary database instance before switching over to a secondary database instance.FIG. 5B illustrates an example in which an independent ping is done from theapplication512 to thedatabase instance508 as part of the callback method. If the independent ping comes up with an indication that thedatabase instance508 is still running, the application can send a “retry” indication. If theapplication512 is sufficiently convinced that the database instance is down, a “OK” callback response can be sent.
• Any callback method can be implemented by theapplication512. In one example, the multipool manager has a callback interface that can be implemented by any application code.
• FIG. 6 is a diagram illustrating the operation of callbacks of one embodiment. Instep602, it is checked if the connection pool is to be switched as determined by the multipool manager. If the connect pool is not to be switched, the connection is done to the connection pool instep604. If the connection is to be switched, then instep606, it is checked whether a callback is indicated for the condition. If no callback is indicated, then the connection is done through the new connection pool without a callback. If a callback is indicated, instep610, a callback is done. If an “OK” indication is received, the connection is done with the new connection pool instep614. If a retry indication is received, a connection is attempted to be done using the old connection pool, instep616. Otherwise, if a “don't reconnect” indication is received, no connection through a connection pool is done inStep618.
• In one embodiment, a multipool manager is adapted to select and set up connections to a database instance through a connection pool. The multipool manager is adapted to check with an application before switching connection pools.
DETAILED DESCRIPTION OF ONE NON-LIMITING EXAMPLE
• The following description gives one non-limiting implementation of multipool implementation. The discussion below gives one embodiment, but those skilled in the art will understand that other implementations of the above-described concepts can be done. Any potentially limitating language given below is to be interpreted in the context of the specific non-limiting implementation and is not meant to limit the general concepts.
• MultiPools can check with the application before failing over to alternate Pools. This is useful if the configured test for the Pool currently in use encounters a random or transient failure, if the application wants to control when a Database Management System (DBMS) instance that's currently not handling clients is brought back into service or if applications can specified an identity when getting connections from Pools, and connections from a matching pool should be returned. This is useful in cases where the DBMS vendor does not provide native support for setting client identities on anonymous JDBC connections.
• A number of improvements can be implemented for multipools.
• • FAILOVER—Existing MultiPool algorithm “HIGH_AVAILABILITY” will be renamed as “FAILOVER”. It will also optionally provide the ability to route application requests for connections to alternative Pools if the current Pool is busy.
  • HEALTH—Existing functionality will be improved to mark dead Pools so that application requests for connections are not routed to these Pools.
  • CALLBACK—A callback interface will be provided to applications to control MultiPool decision to failover to alternative Pools when a failed Pool is detected, or to fail back to Pools previously marked dead.
• Applications can configure a FAILOVER algorithm. FAILOVER can have connections sent through a primary connection pool and have these connections routed through a secondary connection pool upon the failure of the primary connection pool. FAILOVER can optionally also be able to route application requests for connections to alternative Pools if the current Pool is busy.
• In one embodiment, applications will also be able to configure the following MultiPool attribute:

  /**
  * If set, application requests for connections will be routed to
  * alternate pools if current pool is busy. This is only relevant
  * when running with the HIGH_ALGORITHM algorithm. Default
  implies
  * feature is disabled.
  *
  * @param newVal The new attribute value
  * @dynamic
  * @default false
  *
  public boolean isFailoverRequestIfBusy( );
  public void setFailoverRequestIfBusy(boolean failoverRequestIfBusy);

• Applications can be able to implement and register a callback with the system. This callback can be invoked when the MultiPool detects a dead or busy Pool, giving application the ability to control whether MultiPool fails over to an alternative Pool or not.
• In one embodiment, applications will be able to implement the following interface:

  	/**
  	* Application can optionally implement this interface if it wants
  	* to control the failover behavior of WebLogic Server MultiPools.
  	*
  	* If application has registered a class with WebLogic Server that
  	* implements this interface, WebLogic Server will invoke this interface's
  	* method “allowPoolFailover( )” and take different actions depending upon
  	* the return code from the method's invokation.
  	*

  *

  @see

  	weblogic.management.configuration.JDBCMultiPoolMBean#setConnectionPoolFailoverCallbackHandler
  	*/
  	public interface ConnectionpoolFailoverCallback {
  	// name of this interface
  	static   public   final   String   IF_NAME   =
  	“weblogic.jdbc.extensions.ConnectionPoolFailoverCallback”;
  	// opcodes for method ′allowPoolFailover( )′
  	static public final int OPCODE_CURR_POOL_DEAD = 0;
  	static public final int OPCODE_CURR_POOL_BUSY = 1;
  	static public final int OPCODE_REENABLE_CURR_POOL = 2;
  	// return codes for method ′allowPoolFailover( )′
  	static public final int OK = 0; // application is ok with impending action
  	static public final int RETRY_CURRENT = 1; // retry current pool
  	static public final int DONOT_FAILOVER = 2; // do not failover, WLS will
  	throw weblogic.jdbc.extensions.PoolUnavailableSQLException
  	/*
  	* MultiPool will invoke this method under various failover/failback
  	* conditions. Application should return one of the above-defined codes
  	* from this method, based upon application-specific semantics.
  	*
  	* @param currPool - name of connection pool currently in use.
  	* will NEVER be null
  	*
  	* @param nextPool - name of alternate connection pool.
  	* will be null for opcode ′OPCODE_REENABLE_CURR_POOL′
  	*
  	* @param opcode - operation being performed
  	* OPCODE_CURR_POOL_DEAD - ′currPool′ is Dead, MultiPool needs to
  	* failover application requests for connections to ′nextPool′.
  	*
  	* Application should return “OK”, “RETRY_CURRENT” or “DONOT_FAILOVER”,
  	* depending on what it wants the MultiPool to do.
  	*
  	* OPCODE_CURR_POOL_BUSY - ′currPool′ is Busy, MultiPool needs to
  	* re-route application requests for connections to ′nextPool′
  	*
  	* Application should return “OK” if it is ok with this action,
  	* else should return either of the other return codes.
  	*
  	* OPCODE_REENABLE_CURR_POOL - ′currPool′ was previously found
  	* Dead and was consequently disabled. It has now been found healthy,
  	* and MultiPool needs to re-enable it.
  	*
  	* Application should return “OK” if it is ok with this action,
  	* else should return either of the other return codes.
  	*
  	public int allowPoolFailover(String currPool, String nextPool, int opcode);

  }

• Application can register this callback in the attribute “ConnectionPoolFailoverCallbackHandler” of JDBCMultiPoolMBean.

  /**
  * Used to set the absolute name of the application class that implements
  * the interface
  weblogic.jdbc.extensions.ConnectionPoolFailoverCallback.
  *
  * @see weblogic.jdbc.extensions.ConnectionPoolFailoverCallback
  * @non-dynamic
  */
  public String getConnectionPoolFailoverCallbackHandler ( );
  public void setConnectionPoolFailoverCallbackHandler
  (String className);

• Multipools can be enhanced to internally monitor and track the health of the Pools underneath. If a Pool is determined to be dead, it will be marked so and subsequent application requests for connections will not be routed to that Pool.
• In one embodiment, applications will be able to configure the following JDBCMultiPoolMBean attribute:

  	/**
  	* Used to configure the frequency at which the MultiPool checks
  	* the health of connection pools that were previously found
  	* dead and were consequently disabled.
  	*
  	* @param newVal The new attribute value
  	* @dynamic
  	* @default 300
  	*/
  	void setHealthCheckFrequencySeconds (int newVal);
  	int getHealthCheckFrequencySeconds ( );

• Embodiments may be implemented using a conventional general purpose or a specialized digital computer or microprocessor(s) programmed according to the teachings of the present disclosure, as will be apparent to those skilled in the computer art. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art. The invention may also be implemented by the preparation of integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art.
• One embodiment includes a computer program product which is a storage medium (media) having instructions stored thereon/in which can be used to program a computer to perform any of the features presented herein. The storage medium can include, but is not limited to, any type of disk including floppy disks, optical discs, DVD, CD-ROMs, micro drive, and magneto-optical disks, ROMs, Rams, EPROM's, EPROM's, Drams, Rams, flash memory devices, magnetic or optical cards, Nan systems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data.
• Stored on any one of the computer readable medium (media), the present invention includes software for controlling both the hardware of the general purpose/specialized computer or microprocessor, and for enabling the computer or microprocessor to interact with a human user or other mechanism utilizing the results of the present invention. Such software may include, but is not limited to, device drivers, operating systems, execution environments/containers, and user applications.
• The foregoing description of preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to one of ordinary skill in the relevant arts. For example, steps performed in the embodiments of the invention disclosed can be performed in alternate orders, certain steps can be omitted, and additional steps can be added. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims (21)

1. A multipool system to connect to database instances comprising:

multiple connection pools, the connection pools adapted to provide connections to database instances; and

a multipool manager adapted to select and set up connections to a database instance through a connection pool, the multipool manager adapted to keep track of dead connection pools between requests for connections.

2. The multipool system ofclaim 1, wherein the multipool manager tests whether a connection pool has revived.

3. The multipool system ofclaim 2, wherein the test is done in the background asynchronously.

4. The multipool system ofclaim 2, wherein the test is done periodically with a time period that can be set by an application.

5. The multipool system ofclaim 1, wherein the multipool manager sends connections through a primary connection pool preferentially.

6. The multipool system ofclaim 5, wherein there is spillover to a secondary connection pool

7. The multipool system ofclaim 1, wherein the multipool manager load balances connections through multiple connection pools.

8. The multipool system ofclaim 1, wherein the multipool manager check with an application before switching connection pools.

9. The multipool system ofclaim 8, wherein the multipool manager uses a callback interface.

10. The multipool system ofclaim 8, wherein callback information is registered with multipool system by the application.

11. The multipool system ofclaim 1, wherein the multipool manager maintains a list of active connection pools and uses the list to determine what connection pool to connect through.

12. A multipool manager adapted to select and set up connections to a database instance through a connection pool, the multipool manager adapted to keep track of dead connection pools and wherein the multipool manager implements a selection method in which the multipool manager avoids selecting dead connection pools to provide a connection for an application.

13. The multipool manager ofclaim 12, wherein the multipool manager tests whether a connection pool has revived.

14. The multipool manager ofclaim 12, wherein the multipool manager sends connections through a primary connection pool preferentially.

15. The multipool manager ofclaim 12, wherein the multipool manager load balances connections through multiple connection pools.

16. The multipool manager ofclaim 12, wherein the multipool manager checks with an application before switching connection pools.

17. The multipool manager ofclaim 12, wherein the multipool manager adapted to maintain a list of active connection pools and to use the list to determine what connection pool to connect through.

18. A multipool system to connect to database instances comprising:

multiple connection pools, the connection pools adapted to provide connections to database instances; and

a multipool manager adapted to select and set up connections to a database instance through a connection pool, the multipool manager adapted to keep track of dead connection pools and to asynchronously test whether a connection pool is revived.

19. The multipool system ofclaim 18, wherein the multipool manager sends connections through a primary connection pool preferentially.

20. The multipool system ofclaim 18, wherein the multipool manager load balances connections through multiple connection pools.

21. The multipool manager ofclaim 18, wherein the multipool manager checks with an application before switching connection pools.

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