下面是一个使用Apache Samza的示例代码,该代码可以将表格刷新更新到更改日志:
import org.apache.samza.application.StreamApplication;
import org.apache.samza.application.descriptors.StreamApplicationDescriptor;
import org.apache.samza.serializers.JsonSerde;
import org.apache.samza.storage.kv.KeyValueStore;
import org.apache.samza.storage.kv.inmemory.InMemoryKeyValueStore;
import org.apache.samza.table.ReadWriteTable;
import org.apache.samza.table.Table;
import org.apache.samza.table.TableReadFunction;
import org.apache.samza.table.TableWriteFunction;
import org.apache.samza.table.descriptors.TableDescriptor;
import org.apache.samza.table.descriptors.TableDescriptorBuilder;
import org.apache.samza.task.StreamTask;
import org.apache.samza.task.TaskContext;
import org.apache.samza.task.TaskCoordinator;
import org.apache.samza.task.TaskCoordinator.RequestScope;
import org.apache.samza.task.TaskCoordinator.RequestType;
import org.apache.samza.task.WindowableTask;
import org.apache.samza.task.sql.SimpleMessage;
public class TableRefreshExample implements StreamApplication {
private static final String INPUT_TOPIC = "input-topic";
private static final String OUTPUT_TOPIC = "output-topic";
private static final String STATE_STORE_NAME = "state-store";
@Override
public void describe(StreamApplicationDescriptor appDescriptor) {
// 定义输入流和输出流
appDescriptor.getInputStream(INPUT_TOPIC)
.map(this::processRecord)
.sendTo(appDescriptor.getOutputStream(OUTPUT_TOPIC));
// 定义状态存储和表
TableDescriptor tableDescriptor = new TableDescriptorBuilder<>(STATE_STORE_NAME)
.withKeySerde(JsonSerde.of(String.class))
.withValueSerde(JsonSerde.of(String.class))
.withTableReadFunction(StateReadFunction.class)
.withTableWriteFunction(StateWriteFunction.class)
.build();
appDescriptor.getTable(tableDescriptor);
}
private SimpleMessage processRecord(SimpleMessage message) {
// 从表中读取数据
KeyValueStore stateStore = getContext().getStore(STATE_STORE_NAME);
String value = stateStore.get(message.getKey());
// 更新数据
if (value != null) {
value = value + " " + message.getValue();
} else {
value = message.getValue();
}
// 将更新后的数据写回表中
stateStore.put(message.getKey(), value);
return new SimpleMessage(message.getKey(), value);
}
public static class StateReadFunction implements TableReadFunction {
@Override
public String get(String key) {
// 从状态存储中读取数据
KeyValueStore stateStore = getContext().getStore(STATE_STORE_NAME);
return stateStore.get(key);
}
}
public static class StateWriteFunction implements TableWriteFunction {
@Override
public void put(String key, String value) {
// 将数据写入状态存储
KeyValueStore stateStore = getContext().getStore(STATE_STORE_NAME);
stateStore.put(key, value);
// 立即将表格刷新更新到更改日志
TaskCoordinator taskCoordinator = getContext().getTaskCoordinator();
taskCoordinator.commit(RequestScope.ALL_TASKS_IN_CONTAINER, RequestType.ALL);
}
@Override
public void delete(String key) {
// 从状态存储中删除数据
KeyValueStore stateStore = getContext().getStore(STATE_STORE_NAME);
stateStore.delete(key);
// 立即将表格刷新更新到更改日志
TaskCoordinator taskCoordinator = getContext().getTaskCoordinator();
taskCoordinator.commit(RequestScope.ALL_TASKS_IN_CONTAINER, RequestType.ALL);
}
}
}
这个示例代码中,我们定义了一个TableRefreshExample
类,实现了StreamApplication
接口。在describe
方法中,我们定义了输入流和输出流,并且定义了一个名为state-store
的状态存储和表。
在processRecord
方法中,我们从表中读取数据,并根据具体业务逻辑进行数据处理和更新。然后,我们将更新后的数据写回表中。
在StateWriteFunction
中,我们实现了TableWriteFunction
接口的put
和delete
方法,用于将数据写入状态存储和删除数据。在这两个方法中,我们通过TaskCoordinator
的commit
方法将表格刷新更新到更改日志。