Set a cache update policy by using the change tracking feature

Preparations

Create an AccessKey and obtain the AccessKey ID and AccessKey Secret. For more information, see create an AccessKey pair.

Procedure

IntelliJ IDEA (Community Edition 2018.1.4 Windows) is used in this example.

1. Download the SDK package (dts-subscribe-3.0.jar).
2. Add the dts-subscribe-3.0.jar package to the project dependencies.
   1. Open IntelliJ IDEA, choose File > New > Project, and then create a Maven project.
   2. In the menu bar, choose File > Project Structure.
   3. In the left-side navigation pane, click Modules. On the right side of the page, choose > 1 JARs or directories.
   4. Select the dts-subscribe-3.0.jar package and add it to the project dependencies.
      
3. Perform the following steps to set a cache update policy for a MongoDB or Redis database:
   • Run the demo code for MongoDB
     1. Double-click the pom.xml file and add the following settings to the file:

        <dependencies>
            <dependency>
                <groupId>com.vividsolutions</groupId>
                <artifactId>jts</artifactId>
                <version>1.13</version>
            </dependency>
            <dependency>
                <groupId>org.mongodb</groupId>
                <artifactId>mongo-java-driver</artifactId>
                <version>3.2.0</version>
            </dependency>
        </dependencies>

     2. Save the settings and wait for the dependencies to be loaded.
        Note We recommend that you enable IntelliJ IDEA to update Maven dependencies.
     3. Create a Java class file named DTSMySQL2Mongo in the Maven project.
     4. Download the demo code for MongoDB.
     5. Copy the downloaded demo code and replace the existing content in the DTSMySQL2Mongo file with the demo code.
     6. Edit the code in the DTSMySQL2Mongo file and set the parameters.

        Parameter	Description
        accessKey	Enter the AccessKey ID and AccessKey secret of the Alibaba Cloud account. For more information, see Before you begin.
        accessSecret
        Subscription_Instance_ID	Enter the ID of the change tracking instance. To obtain the ID of the change tracking instance, perform the following steps: Log on to the DTS console. In the left-side navigation pane, click Change Tracking.
        mongUrl	Enter the connection string of the MongoDB database and the name of the authentication database. The format is <Connection string>:<Service port number>/<Authentication database name>, for example, ds-bp********-pub.mongodb.rds.aliyuncs.com:3717/admin.
        mongUserName	Enter the database account of the MongoDB database. Note The database account must have the read/write permissions on the destination database. For example, if the tracked data is written to a MongoDB database named testdata, the database account must have the read/write permissions on the testdata database.
        mongUserPassword	Enter the password of the database account.

     7. In the menu bar of IntelliJ IDEA, choose Run > Run to run the program.
   • Run the demo code for Redis
     1. Double-click the pom.xml file and add the following settings to the file:

        <dependencies>
            <dependency>
                <groupId>com.vividsolutions</groupId>
                <artifactId>jts</artifactId>
                <version>1.13</version>
            </dependency>
            <dependency>
                <groupId>redis.clients</groupId>
                <artifactId>jedis</artifactId>
                <version>2.7.2</version>
            </dependency>
        </dependencies>

     2. Save the settings and wait for the dependencies to be loaded.
        Note We recommend that you enable IntelliJ IDEA to update Maven dependencies.
     3. Create a Java class file named DTSMySQL2Redis in the Maven project.
     4. Download the demo code for Redis.
     5. Copy the downloaded demo code and replace the existing content in the DTSMySQL2Redis file with the demo code.
     6. Edit the code in the DTSMySQL2Redis file and set the parameters.

        Parameter	Description
        accessKey	Enter the AccessKey ID and AccessKey secret of the Alibaba Cloud account. For more information, see Before you begin.
        accessSecret
        Subscription_Instance_ID	Enter the ID of the change tracking instance. To obtain the ID of the change tracking instance, perform the following steps: Log on to the DTS console. In the left-side navigation pane, click Change Tracking.
        redisPassword	Enter the database password of the Redis database. Note If a password is set for the Redis database, you must change the code in line 73 from pool = new JedisPool(config, redisUrl, redisPort, 3000); to pool = new JedisPool(config, redisUrl, redisPort, 3000,redisPassword).
        redisPort	Enter the service port number of the Redis database. The default port number is 6379.
        redisUrl	Enter the endpoint (domain name or IP address) of the Redis database.

     7. In the menu bar of IntelliJ IDEA, choose Run > Run to run the program.
4. When the program runs, it retrieves incremental data from the source database and writes the data to the MongoDB or Redis database.