Andrea Cosentino created CAMEL-23630:
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Summary: camel-dapr - add HeaderFilterStrategy and avoid copying
routing-relevant CloudEvent fields into Camel exchange headers
Key: CAMEL-23630
URL: https://issues.apache.org/jira/browse/CAMEL-23630
Project: Camel
Issue Type: Improvement
Reporter: Andrea Cosentino
Assignee: Andrea Cosentino
camel-dapr does not currently ship a HeaderFilterStrategy. Sibling messaging
components such as camel-iggy (IggyHeaderFilterStrategy), camel-kafka
(KafkaHeaderFilterStrategy), and camel-jms (JmsHeaderFilterStrategy) all
provide one to keep external message metadata from colliding with the
component's own "Camel*"-prefixed configuration headers.
Today, DaprPubSubConsumer.createServiceBusExchange(CloudEvent) copies several
CloudEvent fields directly into the exchange as headers:
{code}
cloudEvent.getPubsubName() -> DaprConstants.PUBSUB_NAME
("CamelDaprPubSubName")
cloudEvent.getTopic() -> DaprConstants.TOPIC
("CamelDaprTopic")
cloudEvent.getId() -> DaprConstants.ID
cloudEvent.getSource() -> DaprConstants.SOURCE
cloudEvent.getType() -> DaprConstants.TYPE
cloudEvent.getSpecversion() -> DaprConstants.SPECIFIC_VERSION
cloudEvent.getDatacontenttype() -> DaprConstants.DATA_CONTENT_TYPE
cloudEvent.getBinaryData() -> DaprConstants.BINARY_DATA
cloudEvent.getTime() -> DaprConstants.TIME
cloudEvent.getTraceParent() -> DaprConstants.TRACE_PARENT
cloudEvent.getTraceState() -> DaprConstants.TRACE_STATE
{code}
Two of these headers (CamelDaprPubSubName and CamelDaprTopic) are also read on
the producer side by DaprConfigurationOptionsProxy.getPubSubName / getTopic via
the getOption(...) helper, which prefers header values over the
endpoint-configured destination. As a result, a route such as
{code}
from("dapr-pubsub:configured-pubsub:configured-topic")
.to("dapr-pubsub:configured-pubsub:another-topic");
{code}
will carry the inbound CloudEvent's pubsubName / topic into the producer hop
instead of using the configured destination.
Proposed change (mirrors the camel-iggy pattern):
# Add a DaprHeaderFilterStrategy extending DefaultHeaderFilterStrategy with
in/out filters on the "Camel" / "camel" prefix (lowerCase=true, in/out
FilterStartsWith = DefaultHeaderFilterStrategy.CAMEL_FILTER_STARTS_WITH).
# Expose it via DaprComponent / DaprEndpoint as the standard
headerFilterStrategy URI option, default-instantiated to the new class.
# In DaprPubSubConsumer.createServiceBusExchange(...), either (a) consult the
configured HeaderFilterStrategy before setting each header, or (b) stop copying
PUBSUB_NAME and TOPIC from the inbound CloudEvent, since those constants are
documented as producer-direction routing headers rather than consumer-direction
metadata.
This brings camel-dapr into consistency with the rest of the messaging
component family and removes the consumer-to-producer header carry-over for
routing-relevant fields.
Reference implementation:
components/camel-iggy/src/main/java/org/apache/camel/component/iggy/IggyHeaderFilterStrategy.java
Affects: camel-dapr 4.12.0 through 4.20.0 and current main.
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