davsclaus commented on code in PR #28128:
URL: https://github.com/apache/camel/pull/28128#discussion_r4321905633
##########
docs/user-manual/modules/ROOT/pages/camel-4x-upgrade-guide-4_24.adoc:
##########
@@ -1806,6 +1806,24 @@ the server does not have, with the status code
`Bad_NodeIdUnknown`, and the othe
affected. Previously an awaited write or read completed without an error and
with a `null` body, and a browse failed
with a `NullPointerException`.
+=== camel-milo - the consumer reports a lost connection and refreshes its
values after it
+
+The OPC UA client consumer delivers `Bad_NoCommunication` with a null value
for every monitored node when
+communication with the server is lost, and the current value of every node
once communication is restored. Before,
+the consumer delivered nothing during an outage, and values that did not
change were not delivered again after it.
+
+A consumer that starts while the server cannot be reached, or whose client
cannot connect at all, for example because
+of wrong credentials or an untrusted server certificate, delivers the status
for its nodes too; the cause is in the
+log. A connection that Camel rebuilds after a failed request delivers it for
every node of the connection. Each loss and
+each recovery delivers one exchange per node.
+
+A route that uses only the value of the `DataValue` body receives a null for
these exchanges, which the type converters
+turn into `0` or `false`; a route that stores values checks the status code of
the body first, for example with
+`${body.statusCode.bad}`. A value can now arrive again after an outage, so a
route that counts values, computes
Review Comment:
Since there is deliberately no option, could you add one sentence on how to
keep the previous behaviour, for example
`filter(simple("${body.statusCode.good}"))` right after the consumer? Users
upgrading with routes that write `body.value` straight to a historian will look
for exactly that sentence.
##########
components/camel-milo/src/main/java/org/apache/camel/component/milo/client/internal/SubscriptionManager.java:
##########
@@ -115,25 +116,83 @@ public class SubscriptionManager {
StatusCodes.Bad_SecurityChecksFailed,
StatusCodes.Bad_TcpSecureChannelUnknown,
StatusCodes.Bad_RequestTypeInvalid);
+ /**
+ * The status of a monitored node while communication with the server is
lost: the source of the value is configured
+ * but cannot be reached, and no last value is kept (OPC 10000-8 Table 61,
OPC 10000-14 Table 80).
+ */
+ private static final StatusCode NO_COMMUNICATION = new
StatusCode(StatusCodes.Bad_NoCommunication);
+
private final AtomicLong clientHandleCounter = new AtomicLong();
+ /**
+ * The generation of the last connection built, zero before the first.
+ */
+ private final AtomicLong generationCounter = new AtomicLong();
+
/**
* Listens to the subscription of a connection and to the state of its
session. It is registered on the client
* before the client connects, so that it sees every change of the session
state.
*/
private final class SubscriptionListenerImpl
implements OpcUaSubscription.SubscriptionListener,
SessionActivityListener {
- private volatile boolean sessionActive;
+ /**
+ * The generation of the connection, which orders its values and loss
reports against those of the connection
+ * that replaces it.
+ */
+ private final long generation;
+
+ /**
+ * Whether the session is active. The client connects before the
connection is used, and Milo dispatches the
+ * activity callbacks in the order of the transitions.
+ */
+ private volatile boolean sessionActive = true;
+
+ /**
+ * The subscription of the connection, once it is created.
+ */
+ private volatile OpcUaSubscription subscription;
+
+ SubscriptionListenerImpl(final long generation) {
Review Comment:
Nit: could the constructor move below the `closed` / `lostSessionId` fields,
so all fields are declared together?
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