在i386上使用dds库进行操作，尝试反复提取样本。我明确地在“ read正在”而不是“ take正在”示例，因此它们永远不会过期或被删除。
启动两个黑板应用程序，（1）和（2）
在两个应用程序中都执行读取。这将返回“缓存为空”。
从（1）开始写入，传感器ID：1，事件ID：1，值：1。
从（1）中读取，确认值
从（2）中读取，确认值
从（2）开始写入，传感器ID：1，事件ID：1，值：2。
从（2）中读取，“缓存为空”
从（1）中读取，“缓存为空”
好像我“断”了！我相信样本的生命周期应该是无限的（或者我已经开始理解...但是无法确认！）-但我无法明确设置它。 topicQos.lifespan.duration的类型为Duration_t，但是我无法将其设置为“新的Duration_t(Duration_t.DURATION_INFINITY_SEC,Duration_t.DURATION_INFINITY_NSEC)”，因为它已经完成了？
public class Main {
private static final String EVENT_TOPIC_NAME = "EVENTS";
private static BufferedReader in = null;
private static PrintStream out = null;
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws IOException {
in = new BufferedReader(new InputStreamReader(System.in));
out = new PrintStream(new BufferedOutputStream(System.out));
DomainParticipantFactory factory = DomainParticipantFactory.TheParticipantFactory;
DomainParticipant participant = factory.create_participant(100,
DomainParticipantFactory.PARTICIPANT_QOS_DEFAULT,
null,
StatusKind.STATUS_MASK_NONE);
EventTypeSupport.register_type(participant, EventTypeSupport.get_type_name());
TopicQos topicQos = new TopicQos();
topicQos.durability.direct_communication = true;
topicQos.durability.kind = DurabilityQosPolicyKind.TRANSIENT_DURABILITY_QOS;
topicQos.reliability.kind = ReliabilityQosPolicyKind.RELIABLE_RELIABILITY_QOS;
topicQos.resource_limits.max_instances = 100;
topicQos.resource_limits.max_samples = 100;
topicQos.resource_limits.max_samples_per_instance = 1;
topicQos.ownership.kind = OwnershipQosPolicyKind.SHARED_OWNERSHIP_QOS;
topicQos.history.kind = HistoryQosPolicyKind.KEEP_LAST_HISTORY_QOS;
topicQos.history.depth = 1;
topicQos.history.refilter = RefilterQosPolicyKind.ALL_REFILTER_QOS;
// Since this is on the same computer, and being typed by a human, we can exepct source timestamps to be useful in ordering
topicQos.destination_order.kind = DestinationOrderQosPolicyKind.BY_SOURCE_TIMESTAMP_DESTINATIONORDER_QOS;
Topic topic =
participant.create_topic(EVENT_TOPIC_NAME,
EventTypeSupport.get_type_name(),
topicQos,
new EventTopicListener(),
StatusKind.STATUS_MASK_ALL);
exitIfNullBecause(topic, "Could not create topic");
Subscriber subscriber = participant.create_subscriber(DomainParticipant.SUBSCRIBER_QOS_DEFAULT,
null,
StatusKind.STATUS_MASK_NONE);
exitIfNullBecause(subscriber, "Could not create subscriber");
DataReader reader = subscriber.create_datareader(participant.lookup_topicdescription(EVENT_TOPIC_NAME),
subscriber.DATAREADER_QOS_USE_TOPIC_QOS,
null,
StatusKind.STATUS_MASK_NONE);
exitIfNullBecause(reader, "Could not create reader");
EventDataReader eventReader = (EventDataReader) reader;
Publisher publisher = participant.create_publisher(DomainParticipant.PUBLISHER_QOS_DEFAULT,
null,
StatusKind.STATUS_MASK_NONE);
exitIfNullBecause(publisher, "Could not create publisher");
DataWriter writer = publisher.create_datawriter(topic,
publisher.DATAWRITER_QOS_USE_TOPIC_QOS,
null,
StatusKind.STATUS_MASK_NONE);
exitIfNullBecause(writer, "Could not create writer");
EventDataWriter eventWriter = (EventDataWriter)writer;
boolean loop = true;
byte inputBuffer[] = new byte[1024];
String command;
while(loop){
print("Enter action [read|write|exit]: ");
command = in.readLine();
if(command.startsWith("r")){
dumpCache(eventReader);
} else if(command.startsWith("w")) {
writeCache(eventWriter);
} else if(command.startsWith("e")){
println("exiting...");
System.exit(0);
} else {
println("Unknown: '" + command + "'");
}
}
System.exit(0);
}
private static void print(String output){
out.print(output);
out.flush();
}
private static void println(String output){
out.println(output);
out.flush();
}
private static void exitIfNullBecause(Object thing, String string) {
if (thing == null) {
println("ERROR: " + string);
System.exit(1);
}
}
private static void dumpCache(EventDataReader eventReader) {
// Something interesting here: I can creat it with a collection as a paramter. TODO: Investigate!
EventSeq eventSeq = new EventSeq();
SampleInfoSeq infoSeq = new SampleInfoSeq();
Event event = null;
SampleInfo info = null;
try{
eventReader.read(eventSeq, infoSeq, 100, SampleStateKind.ANY_SAMPLE_STATE, ViewStateKind.ANY_VIEW_STATE, InstanceStateKind.ANY_INSTANCE_STATE);
} catch (Exception e){
println("Cache is empty");
return;
}
Iterator<SampleInfo> infoIter = infoSeq.iterator();
out.printf("| Sensor ID | Event ID | Value |\n");
for(int i=0; i<infoSeq.size(); i++){
event = (Event)eventSeq.get(i);
out.printf("| %9d | %8d | %5d |\n", event.sensor_id, event.event_id, event.value);
}
out.flush();
}
private static void writeCache(EventDataWriter eventWriter) throws IOException {
Event event = new Event();
print("Sensor ID: ");
String sensor_id_str = in.readLine();
print("Event ID: ");
String event_id_str = in.readLine();
print("Value: ");
String value_str = in.readLine();
Event sample = new Event();
sample.sensor_id = Integer.parseInt(sensor_id_str);
sample.event_id = Integer.parseInt(event_id_str);
sample.value = Integer.parseInt(value_str);
InstanceHandle_t handle = eventWriter.register_instance(sample);
// eventWriter.write(sample, handle);
eventWriter.write_w_timestamp(sample, handle, Time_t.now());
out.printf("SensorID: %s, EventID: %s, Value: %s\n",sensor_id_str,event_id_str,value_str); out.flush();
}
}
最佳答案
该问题似乎与lifespan无关。
我不确定您使用的是哪种DDS实现，但是根据DDS规范，您是否在dumpCache方法中执行零复制操作。如果您忘记退还贷款，则您使用的实现可能会像这样。
读/取零副本后，通常应return_loan。
因此，请在dumpCache方法的末尾添加以下代码：
try{
eventReader.return_loan(eventSeq, infoSeq);
} catch (Exception e){
println("Error returning loan");
return;
}
关于java - DDS DataReader缓存中断，无法再访问，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/4108830/