Add Custom Attribute with Auto Instrumentation

[codeforaliving]

We are currently using Open Telemetry auto instrumentation with a Java extension (just a SpanProcessor for now) to rename span names as well as redact sensitive info from the url. Now we want to add a custom attribute to our traces and spans.

We currently have a servlet filter to add the transaction id to the current span, but I am not sure how to propagate that value to child spans and I am not seeing the value at all in XRay. We are using Spring Boot and exporting through Prometheus.

Any suggestions on how to get a custom attribute propagated?

[trask]

hi @codeforaliving! you could do something like https://github.com/microsoft/ApplicationInsights-Java/blob/main/agent/agent-tooling/src/main/java/com/microsoft/applicationinsights/agent/internal/init/InheritedAttributesSpanProcessor.java

also check out #6191 and open-telemetry/oteps#207

[codeforaliving]

Hello @trask . Is this the correct way to add something to Baggage?

Baggage.current().toBuilder().put("my-transaction-id", transactionId).build().storeInContext(Context.current()).makeCurrent();

[trask]

make sure to use makeCurrent via try-with-resources to make sure that it is closed

[codeforaliving]

make sure to use makeCurrent via try-with-resources to make sure that it is closed

@trask thanks for the response. So essentially wrap the entire call in a try-with-resources? Will that still allow Baggage to be retrieved in our custom extension?

[codeforaliving]

@trask When I make the call via try-with-resources, I am unable to access the value from Baggage in my custom extension. For example:

try (Scope ignored = Context.current().with(Baggage.current().toBuilder().put("foo", "bar").build()).makeCurrent()) { // what should I do here? }

[laurit]

try (Scope ignored = Context.current().with(Baggage.current().toBuilder().put("foo", "bar").build()).makeCurrent()) { // what should I do here? }

Assuming you are using it in a servlet filter you should be calling filterChain.doFilter(request, response); there. This way the baggage you added in the context will be available during the request processing and will be cleared when the request is done.

[codeforaliving]

@laurit thanks for the response. We have a class that adds a transaction ID to ThreadLocal and that is where I wanted to put the baggage logic. Can’t something just be added to baggage without the auto close?

[laurit]

We encourage people to use try with resource to ensure that the scope returned from makeCurrent() is closed. If you don't want to use try with resource then it is fine as long as you close the scope manually or verify yourself that you don't have a memory leak.

[codeforaliving]

@laurit Thanks again for the response. Do you think it is sufficient to use the try-with-resources when extracting the Baggage items and adding them to a span in our custom SpanProcessor extension? In other words, after we extract the Baggage from the parent context and determine that the value is there, perform the following:

...
final String transactionId = Baggage.fromContext(parentContext).getEntryValue("transaction-id");
try (Scope ignored = baggage.makeCurrent()) {
     span.setAttribute("transaction-id", transactionId);
}
...

[laurit]

I don't see how this could help. Baggage.fromContext(parentContext) finds the current baggage from context, no need to call makeCurrent on it again. span.setAttribute doesn't do anything with context so changing the context with makeCurrent shouldn't be needed. Just

final String transactionId = Baggage.fromContext(parentContext).getEntryValue("transaction-id");
span.setAttribute("transaction-id", transactionId);

should be enough.