Bjorn Beskow created CAMEL-23349:
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Summary: Camel OpenTelemetry2 programmatic baggage management
Key: CAMEL-23349
URL: https://issues.apache.org/jira/browse/CAMEL-23349
Project: Camel
Issue Type: Improvement
Components: camel-opentelemetry
Affects Versions: 4.19.0, 4.18.1
Reporter: Bjorn Beskow
With Camel OpenTelemetry2 and OpenTelemetry spring boot starter, most aspects
of Span Customization such as adding attributes, events and creating nested
spans can be done using the OpenTelemetry apis. Programmatically adding OTEL
baggage is however an exception. The typical use case for OTEL baggage is to
allow for small pieces of contextual data that need to travel with a request
across distributed service boundaries, independent of any single span. In our
business context, it is in the form of a "business correlation id" that is
captured from a header or from the message payload as the very first processor
of a boundary component, and should be available to all downstream components.
The OTEL api itself cannot easily be used to add baggage items to a Camel
route, due to `Scope` handling: Baggage must be added to a baggage scope, and
is visible and propagated during the lifetime of the scope. The OTEL api looks
like this:
// Create baggage with an entry
Baggage baggage = Baggage.current().builder()
.put("user-id", "12345")
.build();
// Attach baggage to current context
Context contextWithBaggage = Context.current().with(baggage);
// Make it current (scoped)
try (var scope = contextWithBaggage.makeCurrent()) {
// Your code here - baggage is now active
}
Doing this in a processor, the scope instance must be kept open as long as
needed, typically until the end of the exchange. In theory, the following
simple albeit brittle solution should work:
Baggage baggage = Baggage.current().toBuilder()
.put("user-id", "12345")
.build();
Context ctxWithBaggage = Context.current().with(baggage);
Scope scope = ctxWithBaggage.makeCurrent();
exchange.getExchangeExtension().addOnCompletion(new SynchronizationAdapter() {
@Override public void onDone(Exchange exchange) {
scope.close();
}
});
In practice however, this doesn't work. A (final) baggage scope is already
(automatically) created at the start of a Camel route execution, stored on the
exchange as part of a wrapped instance of
org.apache.camel.opentelemetry2.OpenTelemetrySpanAdapter and properly closed at
the end of the route. It is that scope that is passed to the OTEL propagator,
not the scope created programmatically as in the example above.
Hence to my understanding, the simplest way to programmatically add baggage
items would be to allow for mutating the Baggage scope stored in the
org.apache.camel.opentelemetry2.OpenTelemetrySpanAdapter. The required pieces
are already present, but would need to be exposed in a public API (currently,
both context, baggage and baggage scope are protected).
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