Sun Java System Message Queue 4.1 Administration Guide

Configuring a Persistent Data Store

A broker’s persistent data store holds information about physical destinations, durable subscriptions, messages, transactions, and acknowledgments. Message Queue brokers are configured by default to use a file-based persistent store, but you can reconfigure them to plug in any data store accessible through a JDBC-compliant driver. The broker configuration property imq.persist.store (see Table 14–4) specifies which of the two forms of persistence to use.

Configuring a File-Based Store

A file-based data store is automatically created when you create a broker instance. The store is located in the broker’s instance directory; see Appendix A, Platform-Specific Locations of Message Queue Data for the exact location.

By default, Message Queue performs asynchronous write operations to disk. The operating system can buffer these operations for efficient performance. However, if an unexpected system failure should occur between write operations, messages could be lost. To improve reliability (at the cost of reduced performance), you can set the broker property imq.persist.file.sync to write data synchronously instead. For further discussion about this property, see File-Based Persistence and Table 14–5.

When you start a broker instance, you can use the imqbrokerd command’s -reset option to clear the file system store. For more information about this option and its suboptions, see Broker Utility.

Configuring a JDBC-Based Store

To configure a broker to use JDBC-based persistence, you set JDBC-related properties in the broker’s instance configuration file and create the appropriate database schema. The Message Queue Database Manager utility (imqdbmgr) uses your JDBC driver and the broker configuration properties to create the schema and manage the database. You can also use the Database Manager to delete corrupted tables from the database or if you want to use a different database as a data store. See Database Manager Utility for more information.

Note –

Example configurations are available for HADB, Java DB (Apache Derby), Oracle, and MySQL database products. The location of these files is platform-dependent, and is listed under “Example applications and configurations” in the relevant tables of Appendix A, Platform-Specific Locations of Message Queue Data. In addition, examples for Oracle are provided as commented-out values in the instance configuration file, config.properties, and for MySQL in the default broker configuration file, default.properties.

To Configure a JDBC-Based Data Store

Set JDBC-related properties in the broker’s instance configuration file.

The relevant properties are discussed under JDBC-Based Persistence and listed in Table 14–6. In particular, you must set the broker’s imq.persist.store property to jdbc (see Persistence Properties).

Place a copy of, or a symbolic link to, your JDBC driver’s .jar file in the following location, depending on your platform:
For example, if you are using HADB on a Solaris system, the following command copies the driver’s .jar file to the appropriate location:
```
   
cp  /opt/SUNWhadb/4/lib/hadbjdbc4.jar  /usr/share/lib/imq/ext
```
The following command creates a symbolic link instead:
```
   
ln  -s  /opt/SUNWhadb/4/lib/hadbjdbc4.jar  /usr/share/lib/imq/ext
```

Create the database schema needed for Message Queue persistence.

Use the imqdbmgr create all command (for an embedded database) or the imqdbmgr create tbl command (for an external database); see Database Manager Utility.
1. Change to the directory where the Database Manager utility resides, depending on your platform:
2. Enter the imqdbmgr command:
```
   
imqdbmgr create all
```
  Note –
  If you use an embedded database, it is best to create it under the following directory:
```
   
.../instances/instanceName/dbstore/databaseName
```
  If an embedded database is not protected by a user name and password, it is probably protected by file system permissions. To ensure that the database is readable and writable by the broker, the user who runs the broker should be the same user who created the embedded database using the imqdbmgr command.

Displaying Information About the Persistent Store

The query subcommand of the Database Manager utility (imqdbmgr) displays information about the persistent store, including the store version, the database user, and whether the database tables have been created. Example 4–1 shows an example of the output.

Example 4–1 Displaying Persistent Store Information

dbmgr query

[04/Oct/2005:15:30:20 PDT] Using plugged-in persistent store:
        version=400
        brokerid=Mozart1756
        database connection url=jdbc:oracle:thin:@Xhome:1521:mqdb
        database user=scott
Running in standalone mode.
Database tables have already been created.

Securing Persistent Data

The persistent store can contain, among other information, message files that are being temporarily stored. Since these messages may contain proprietary information, it is important to secure the data store against unauthorized access. This section describes how to secure data in a file-based or JDBC-based data store.

Securing a File-Based Store

A broker using file-based persistence writes persistent data to a flat-file data store whose location is platform-dependent (see Appendix A, Platform-Specific Locations of Message Queue Data):

   …/instances/instanceName/fs370

where instanceName is a name identifying the broker instance. This directory is created when the broker instance is started for the first time. The procedure for securing this directory depends on the operating system platform on which the broker is running:

On Solaris and Linux, the directory’s permissions are determined by the file mode creation mask (umask) of the user who started the broker instance. Hence, permission to start a broker instance and to read its persistent files can be restricted by setting the mask appropriately. Alternatively, an administrator (superuser) can secure persistent data by setting the permissions on the instances directory to 700.
On Windows, the directory’s permissions can be set using the mechanisms provided by the Windows operating system. This generally involves opening a Properties dialog for the directory.

Securing a JDBC-Based Store

A broker using JDBC-based persistence writes persistent data to a JDBC-compliant database. For a database managed by a database server (such as Oracle), it is recommended that you create a user name and password to access the Message Queue database tables (tables whose names start with IMQ). If the database does not allow individual tables to be protected, create a dedicated database to be used only by Message Queue brokers. See the documentation provided by your database vendor for information on how to create user name/password access.

The user name and password required to open a database connection by a broker can be provided as broker configuration properties. However it is more secure to provide them as command line options when starting up the broker, using the imqbrokerd command’s -dbuserand -dbpassword options (see Broker Utility).

For an embedded database that is accessed directly by the broker by means of the database’s JDBC driver, security is usually provided by setting file permissions on the directory where the persistent data will be stored, as described above under Securing a File-Based Store To ensure that the database is readable and writable by both the broker and the Database Manager utility, however, both should be run by the same user.