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An accurate concurrency control on multiple web application servers

IP.com Disclosure Number: IPCOM000132440D
Original Publication Date: 2005-Dec-16
Included in the Prior Art Database: 2005-Dec-16
Document File: 1 page(s) / 9K

Publishing Venue

IBM

Abstract

A method, which can control accurately the system-wide concurrency level of transactions that are classified into groups according to their service level requirements on a Web-based system and can allow skewed workload allocation that are generally unavoidable because general Web servlet programs require session sticky characteristics, is disclosed. This method is another one to achieve the accurate system-wide concurrency level control, which can also be achieved by the invention filed as JP9-2004-0227.

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An accurate concurrency control on multiple web application servers

 A method, which can control accurately the system-wide concurrency level of transaction groups on a Web-based system and can allow skewed workload allocation, is disclosed. A mission critical system generally consists of transactions of various loads. When a mission critical system is implemented on a Web-based system, it is difficult to make the system stable because the Web-based system does not have a fine workload control function that can control the system load while the system has transactions of various loads running concurrently. It is necessary for a fine workload control function that it can control system-wide concurrency levels of transactions classified into groups according to their service level requirements. Generally speaking, transactions which are used in a session by a user have to pass data to next transactions using session object. Therefore they require session sticky characteristics, which mean all transactions in a session have to be executed on a same application server. It results skewed workload allocation among a plural of Web application servers.

 There is assumed to be a fine feed-forward workload control function called "Group Flow Control" on each web application server. In brief, GFC does the following as an extension of a web application framework such as Struts that is implemented by Apache Struts project.

1) Sorts transactions into groups with similar priorities and characteristics.
2) Controls the concurrency level of these groups according to their service level requirements.

 When a transaction arrives on a Web application server on which the current concurrency level of its transaction group reaches the local upper limit of the concurrency level, it will wait for a pre-defined interval or will be cancelled according to the pre-defined action for each group.

The method of JP9-2004-0227 controls the system-wide concurrency level as follows in brief.
1) Assigns a little larger maximum concurrency level than the average expected concurrency level for each transaction group on each local web application server.
2) Monitors the current concurrency level of each group every pre-specified short intervals. If the sum of the local current concurrency level of a group reaches or exceeds the system-wide maximum concurrency level target of the group, decreases the maximum concurrency level of the group on each web application server to the current concurrency level of the group on itself. Oth...