2025-04-17 clj-otel | Clojure Slack Archive

clj-otel 2025-04-17

kenny 2025-04-17T14:42:26.642389Z

I’m adding tracing in a concurrent app where parent tasks spawn child tasks. However, I’m facing an issue where child task spans aren’t properly attached to their parent spans. My initial approach looks like this:

(defn start-task!
  []
  (span/with-span! :start-task 
    (let [do-sub-task (fn [sub-task] 
                        (span/with-span! :sub-task 
                          ;; do work
                          ))
          sub-tasks []]
      (doseq [sub-task sub-tasks] (submit! executor do-sub-task sub-task)))))

This results in disconnected traces - the sub-task spans aren’t linked to the parent span in trace visualizations. I found that explicitly passing the context to child tasks resolves the issue:

(defn start-task!
  []
  (span/with-span! :start-task
    (let [ctx (context/dyn)
          do-sub-task (fn [sub-task]
                        (span/with-span! {:name :sub-task :parent ctx}
                          ;; do work
                          ))
          sub-tasks []]
      (doseq [sub-task sub-tasks] (submit! executor do-sub-task sub-task)))))

Question Is explicitly capturing and passing the parent context the recommended pattern for preserving trace relationships across concurrent boundaries? Are there alternative approaches or best practices I should consider? Is this best done by using the steffan-westcott.clj-otel.context API?

kenny 2025-04-18T13:33:23.821529Z

thx!

kenny 2025-04-17T14:45:23.818899Z

Another approach I tried was using (span/get-span-context).

(defn start-task!
  []
  (span/with-span! :start-task
    (let [ctx (span/get-span-context)
          do-sub-task (fn [sub-task]
                        (span/with-span! {:name :sub-task :parent ctx}
                          ;; do work
                          ))
          sub-tasks []]
      (doseq [sub-task sub-tasks] (submit! executor do-sub-task sub-task)))))

However, this throws an exception.

class io.opentelemetry.api.internal.AutoValue_ImmutableSpanContext cannot be cast to class io.opentelemetry.context.Context (io.opentelemetry.api.internal.AutoValue_ImmutableSpanContext

steffan 2025-04-17T15:11:01.448949Z

As https://cljdoc.org/d/com.github.steffan-westcott/clj-otel-api/0.2.7/doc/concepts#_instrumenting_asynchronous_clojure_code, when manually instrumenting asynchronous code, use either explicit context passing or the bound context value. The second code sample you gave is a good example of the explicit context passing approach.

steffan 2025-04-17T15:18:09.333729Z

To compare the two approaches, look for the bound-async and explicit-async directories in each of the microservices examples. Here is one example : https://github.com/steffan-westcott/clj-otel/tree/master/examples/microservices/auto-instrument/middleware/sentence-summary-service/src/example/sentence_summary_service

steffan 2025-04-17T15:25:50.176199Z

For further description of context, current context and bound context please see https://cljdoc.org/d/com.github.steffan-westcott/clj-otel-api/0.2.7/doc/concepts#_context.

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clj-otel 2025-04-17