Consider using `serial_test` for test modules using subscribers

[eureka-cpu]

Running the append_blob_client.rs tests produces these errors, but they can be avoided by running them serially with https://docs.rs/serial_test/latest/serial_test/:

     Running tests/append_blob_client.rs (target/debug/deps/append_blob_client-6634ef5a7bf23216)

running 11 tests
test test_append_block ... FAILED
test test_create_append_blob ... FAILED
test test_append_block_position_condition ... FAILED
test test_create_append_blob_with_tags ... FAILED
test test_create_append_blob_if_not_exists ... FAILED
test test_append_block_from_url_source_if_match ... FAILED
test test_append_block_max_size_condition ... FAILED
test test_append_block_transactional_checksums ... FAILED
test test_create_append_blob_content_headers ... FAILED
test test_seal_append_blob ... FAILED
test test_append_block_from_url ... FAILED

failures:

---- test_append_block stdout ----

thread 'test_append_block' (86742) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_create_append_blob stdout ----

thread 'test_create_append_blob' (86748) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_append_block_position_condition stdout ----

thread 'test_append_block_position_condition' (86746) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_create_append_blob_with_tags stdout ----

thread 'test_create_append_blob_with_tags' (86751) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_create_append_blob_if_not_exists stdout ----

thread 'test_create_append_blob_if_not_exists' (86750) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_append_block_from_url_source_if_match stdout ----

thread 'test_append_block_from_url_source_if_match' (86744) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_append_block_max_size_condition stdout ----

thread 'test_append_block_max_size_condition' (86745) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_append_block_transactional_checksums stdout ----

thread 'test_append_block_transactional_checksums' (86747) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_create_append_blob_content_headers stdout ----

thread 'test_create_append_blob_content_headers' (86749) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_seal_append_blob stdout ----

thread 'test_seal_append_blob' (86752) panicked at /home/eureka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tracing-subscriber-0.3.23/src/fmt/mod.rs:520:14:
Unable to install global subscriber: SetGlobalDefaultError("a global default trace dispatcher has already been set")

---- test_append_block_from_url stdout ----

thread 'test_append_block_from_url' (86743) panicked at sdk/core/azure_core_test/src/proxy/mod.rs:198:32:
endpoint not set
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[github-actions]

Thank you for your feedback. Tagging and routing to the team members best able to assist. cc @vincenttran-msft, @jalauzon-msft, @jaschrep-msft

Generated by Agentic Triage for issue #4530 · ● 2.4M · ◷

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gh aw add githubnext/agentics/workflows/issue-triage.md@8e6d7c86bba37371d2d0eee1a23563db3e561eb5

[github-actions]

🎯 Agentic Issue Triage

Summary: Tests in append_blob_client.rs fail when run in parallel because multiple tests each try to install a global tracing-subscriber, which panics after the first one succeeds. The author suggests using the serial_test crate to force serial execution.

📋 Issue Details

• Crate / module: azure_storage_blob / tests/append_blob_client.rs
• Affected API: tracing-subscriber global dispatcher initialization in test setup
• Scenario: Running cargo test for the storage blob append blob integration tests
• Root ask: Fix the test suite so tests pass when run in parallel, either by using serial_test or by refactoring test setup to avoid global subscriber conflicts

🔎 Debugging / Reproduction Notes

All 11 tests panic with SetGlobalDefaultError("a global default trace dispatcher has already been set") because each test tries to call set_global_default (via tracing-subscriber) concurrently. One test (test_append_block_from_url) additionally panics with endpoint not set, suggesting it has an additional setup issue.

Suggested investigation steps:

1. Check test setup in tests/append_blob_client.rs — look for each test calling tracing_subscriber::fmt::init() or similar.
2. Evaluate using #[serial] from the serial_test crate, or switching to tracing_subscriber::try_init() to avoid panicking on duplicate initialization.
3. Consider a shared once_cell/std::sync::OnceLock guard for subscriber initialization so parallel tests don't conflict.

🏷️ Label Confidence

• Category: Client — azure_storage_blob does not start with azure_resourcemanager_
• Service: Storage — issue is in sdk/storage/ / append blob client tests
• Confidence: High — explicit reference to append_blob_client.rs in the storage SDK

👥 Owner Routing

• Matched CODEOWNERS entry: # ServiceLabel: %Storage — matched because the predicted service label is Storage
• AzureSDKOwners: @vincenttran-msft, @jalauzon-msft, @jaschrep-msft
• ServiceOwners: none listed
• Routing action: Assigned to vincenttran-msft (randomly selected from AzureSDKOwners); added needs-team-attention due to customer-reported

Generated by Agentic Triage for issue #4530 · ● 2.4M · ◷

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/issue-triage.md@8e6d7c86bba37371d2d0eee1a23563db3e561eb5