Marco Collovati created CAMEL-15748:
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Summary: Paho consumer never connects if the broker is not
reachable at startup
Key: CAMEL-15748
URL: https://issues.apache.org/jira/browse/CAMEL-15748
Project: Camel
Issue Type: Bug
Components: camel-paho
Affects Versions: 3.6.0, 3.4.4, 3.5.0
Reporter: Marco Collovati
Having a route with a paho consumer in a route, if the broker is not reachable
at startup, camel context fail fast and shuts down.
This can be avoided by setting the *SupervisingRouteController*, but this way,
even if camel context does not fail, the consumer is never able to establish a
connection.
The reason is that when *PahoConsumer* starts for the first time, it creates a
*MqttClient* and stores it into *client* field; the call to *client.connect*
throws an exception due to broker down;
{code:java}
@Override
protected void doStart() throws Exception {
super.doStart(); connectOptions =
PahoEndpoint.createMqttConnectOptions(getEndpoint().getConfiguration());
if (client == null) {
clientId = getEndpoint().getConfiguration().getClientId();
if (clientId == null) {
clientId = "camel-" + MqttClient.generateClientId();
}
stopClient = true;
client = new MqttClient(
getEndpoint().getConfiguration().getBrokerUrl(),
clientId,
PahoEndpoint.createMqttClientPersistence(getEndpoint().getConfiguration()));
LOG.debug("Connecting client: {} to broker: {}", clientId,
getEndpoint().getConfiguration().getBrokerUrl());
client.connect(connectOptions);
}
// other code omitted for brevity
client.subscribe(getEndpoint().getTopic(),
getEndpoint().getConfiguration().getQos());{code}
after that *doStop* is invoked but the *client* instance is not nullified,
because it is not connected
{code:java}
@Override
protected void doStop() throws Exception {
super.doStop(); if (stopClient && client != null &&
client.isConnected()) {
String topic = getEndpoint().getTopic();
// only unsubscribe if we are not durable
if (getEndpoint().getConfiguration().isCleanSession()) {
LOG.debug("Unsubscribing client: {} from topic: {}", clientId,
topic);
client.unsubscribe(topic);
} else {
LOG.debug("Client: {} is durable so will not unsubscribe from
topic: {}", clientId, topic);
}
LOG.debug("Disconnecting client: {} from broker: {}", clientId,
getEndpoint().getConfiguration().getBrokerUrl());
client.disconnect();
client = null;
}
}
{code}
when the supervisor tries to restart the route, *client* instance already
exists, but the call to *client.subscribe* fails because the client is not
connected.
Perhaps always nullify *client* in *doStop* should resolve the issue; however I
have no idea it this solution will impact in other ways.
A better solution may be to handle automatic reconnect in the consumer, like
*RabbitConsumer* does, for example.
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