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How to Define the Timeout of a Query

Bulbgraph.png   This feature is available from PR14Q2

Contents

Introduction

Defining the timeout of a query allows to cancel its execution once a certain amount of time has passed since it was started. This helps to protect the database by preventing queries from being stalled.

QueryTimeOutUtil class

The QueryTimeOutUtil class provides setQueryTimeOut methods that defines the timeout of:

The first argument of the setQueryTimeOut method is the object whose query timeout is to be set. The second argument is a string that represents a timeout profile (see next section).

This class also provides resetQueryTimeOut methods to reset the timeout to 0.

Timeout profiles

Query timeouts are defined using timeout profiles. A timeout profile represents a server-side activity. For instance, the GRID timeout profile, defined in core, is used by the DefaultJsonDataService in the queries that are done to retrieve the records that will be shown in the grid.

Query timeouts are declared in the Openbravo.properties file, using the db.queryTimeout.<profile_name>=#profile_timeout_in_seconds. For instance to define a new profile called MY_PROCESS with a query timeout of 5 seconds, the following line must be added to Openbravo.properties:

db.queryTimeout.MY_PROCESS=5

If the timeout is set to 0, the queries that use that profile will not have a limit in its execution time. Core timeout profiles are set to 0 by default.

Openbravo defines in its core these timeout profiles:

If you create a process and do not set a query profile for its queries, the db.queryTimeout.scheduledProcess or db.queryTimeout.manualProcess will be used by default. You can override these default profiles by executing QueryTimeOutUtil.getInstance().setQueryTimeOut on your query.

Example

Let's suppose a developer is using a query that is bound to be time-consuming, so he wants to allow specifying a limit in its execution time. The developer can reuse an existing query profile or create a new one. In this case none of the existing query profiles applies, so he uses a new one that he calls MY_TIME_CONSUMING_QUERY.

String hql = "update ...";
Query qry = OBDal.getInstance().getSession().createQuery(hql);
QueryTimeOutUtil.getInstance().setQueryTimeOut(qry, queryType);
try {
  qry.executeUpdate();
} catch (Exception e) {
  if (e instanceof SQLTimeoutException || e instanceof QueryTimeoutException) {
    // Handle query cancelation due to query timeout
  }
}

If the developer wants to reuse the query object and wants to reset its query timeout, he should execute this command:

QueryTimeOutUtil.getInstance().resetQueryTimeOut(qry);

When the module that contains this code is installed, the query will actually not have any timeout until the db.queryTimeout.MY_TIME_CONSUMING_QUERY parameter is added to Openbravo.properties with a value higher than 0.

Limitations

In PostreSQL, because of a limitation in the driver this feature is not available until 3.0PR15Q4.

Retrieved from "http://wiki.openbravo.com/wiki/How_to_Define_the_Timeout_of_a_Query"

This page has been accessed 3,829 times. This page was last modified on 11 August 2015, at 07:08. Content is available under Creative Commons Attribution-ShareAlike 2.5 Spain License.