Modify

前置阅读

• 创建订阅请看 创建 Subscription.
• 整条订阅启停 / 单 MI 启停请看 SetMonitoringMode.

sub.modify(...)

修改 Subscription 的发布参数 (ModifySubscription 服务):

public ModifySubscriptionResult modify(double publishingIntervalMs);
public ModifySubscriptionResult modify(double publishingIntervalMs,
                                       int lifetimeCount,
                                       int maxKeepAliveCount,
                                       int maxNotificationsPerPublish,
                                       byte priority);

参数	默认 (短重载)	含义
publishingIntervalMs	—	新发布间隔
lifetimeCount	1200	多少个 publish 周期没收到 PublishRequest 就清理订阅
maxKeepAliveCount	50	没新数据时多久发一次空 KeepAlive
maxNotificationsPerPublish	0	单次 Publish 最多发多少条通知, 0 = 不限
priority	0	优先级

返回 ModifySubscriptionResult, 字段:

方法	类型	说明
getRevisedPublishingIntervalMs()	double	服务端实际生效的间隔
getRevisedLifetimeCount()	int	服务端实际生效的 lifetime
getRevisedMaxKeepAliveCount()	int	服务端实际生效的 keepAlive

ModifySubscriptionResult rev = sub.modify(1000.0, 600, 30, 0, (byte) 0);
System.out.println("Revised publishing interval = "
    + rev.getRevisedPublishingIntervalMs() + "ms");

---

sub.modifyMonitoredItems(requests)

批量修改 MI 采样参数 (ModifyMonitoredItems 服务):

public List<ModifyMonitoredItemResult> modifyMonitoredItems(
    List<MonitoredItemModifyRequest> requests);

MonitoredItemModifyRequest 字段:

字段	默认	说明
monitoredItemHandle	—	本地 MI 句柄
samplingIntervalMs	-1	-1 = 跟订阅, 0 = 尽快
queueSize	1	服务端缓冲队列长度
discardOldest	true	true = 丢最旧, false = 丢最新

返回 ModifyMonitoredItemResult:

方法	说明
getStatus()	修改结果
getRevisedSamplingIntervalMs()	服务端实际采样间隔
getRevisedQueueSize()	服务端实际队列大小

import java.util.stream.Collectors;

List<MonitoredItemModifyRequest> requests = miHandles.stream()
    .map(h -> new MonitoredItemModifyRequest(h, 50.0, 10, true))
    .collect(Collectors.toList());

List<ModifyMonitoredItemResult> results = sub.modifyMonitoredItems(requests);
for (ModifyMonitoredItemResult r : results) {
    System.out.println(r);  // ModifyMonitoredItemResult{status=Good, interval=50.0ms, queueSize=10}
}

---

sub.modifyItem(...) 单 MI 简化版

public ModifyMonitoredItemResult modifyItem(int monitoredItemHandle, double samplingIntervalMs);
public ModifyMonitoredItemResult modifyItem(int monitoredItemHandle,
                                            double samplingIntervalMs,
                                            int queueSize,
                                            boolean discardOldest);

ModifyMonitoredItemResult r = sub.modifyItem(handle, 50.0);
System.out.println("Revised sampling = " + r.getRevisedSamplingIntervalMs() + "ms");

---

QueueSize 与 DiscardOldest

服务端为每个 MI 维护一个先进先出队列. 当客户端 Publish 来不及取时, 队列满了:

• discardOldest = true (默认) → 丢最旧, 保留最新
• discardOldest = false → 丢最新, 保留最旧

queueSize = 1 (默认) 只保留最新值, 适合"实时显示"; queueSize = N (N > 1) 适合"采样不能漏"的高频数据.

下一步

• SetMonitoringMode
• Republish