Compat: Add Multi-Azure Function Unique Named Pipe Configuration#20
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Changes: - Add CalculateTracePipeName() and CalculateDogStatsDPipeName() public methods - These methods generate unique pipe names with GUID suffixes - Methods are designed to be instrumented by the Datadog tracer - When tracer is present, instrumentation will override return values - When no tracer, methods work normally generating their own pipe names - Update ConfigureNamedPipes() to call these new methods - Add comprehensive tests for the new pipe name calculation methods This approach allows the tracer to control pipe naming while keeping the compat layer functional in standalone scenarios. Related: SVLS-8244
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When DD_TRACE_PIPE_NAME or DD_TRACE_WINDOWS_PIPE_NAME (and their DogStatsD equivalents) are explicitly set, return the configured name directly. Only append a GUID suffix in auto-discovery mode (no env vars set). This prevents a mismatch where the tracer sends to the explicit pipe name but the compat binary listens on a GUID-suffixed variant. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
ConfigureNamedPipes now sets DD_TRACE_PIPE_NAME and DD_DOGSTATSD_PIPE_NAME in the current process environment, so that in-process consumers like the DogStatsD client can discover the pipe to connect to. This runs during the DOTNET_STARTUP_HOOKS phase, before user code calls DogStatsdService.Configure(), so the env vars are guaranteed to be visible. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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## Summary of changes * Allow use of unique windows named pipes for IPC, coordinated with the serverless compatibility layer's mini-agent. * See: DataDog/datadog-serverless-compat-dotnet#20 for compat-side changes. * See: DataDog/serverless-compat-self-monitoring#54 for integration testing in Azure. ## Reason for change * Improve support for running multiple Azure Functions in the same hosting plan. [[jira](https://datadoghq.atlassian.net/browse/SVLS-8244)] ## Implementation details For [Azure Functions](https://docs.datadoghq.com/serverless/azure_functions/?tab=dotnet#setup), the tracer loads first, then the compat layer, and then the compat layer launches a rust binary to act as the agent. Additionally, the client may or may not be using the DogstatsD client, and it is also possible to have the compat layer and DogstatsD in place without the tracer. We need to coordinate named pipes across all three/four of these codebases, noting that the tracer will use DogstatsD's pipe for runtime metrics if available. Given this order of operations, and that we want this to work with immutable configuration, the tracer should set pipe names for the compatibility layer via instrumentation if the tracer is present. 1. Tracer loads -- pipe name is generated 2. We check the presence of the compat layer + windows configs (using undocumented envvar `DD_SERVERLESS_COMPAT_BINARY_PATH` if necessary to adapt to Azure changes) to see if named pipes can be used or if we should rely on TCP 4. Compat layer loads 5. Tracer uses instrumentation to force the compat layer to generate the pipe names <pipe-a>, <pipe-b> 6. Compat layer passes the name to the mini-agent tracer <pipe-a> and dogstatsd <pipe-b>. | Scenario | Pipe generated? | Transport | Result | |---|---|---|---| | New tracer + no compat at all | No (binary not found) | TCP | Works | | New tracer + old compat (< 1.5) | No (version check fails) | TCP | Works | | New tracer + new compat (≥ 1.5) | Yes | Named pipe | Works (integration coordinates) | | New tracer + dev compat (0.0.0) | Yes | Named pipe | Works (integration coordinates) | | Old tracer + no compat | No | TCP | Works | | Old tracer + old compat (< 1.5) | No | TCP | Works (neither side knows about pipes) | | Old tracer + new compat (≥ 1.5) | No | TCP | **Broken** — tracer sends via TCP, but compat binary listens on pipe only. Requires [more serverless-components changes](DataDog/serverless-components#94). | | Old tracer + dev compat (0.0.0) | No | TCP | Not supported | ## Test coverage * Self Monitoring * New Unit Tests --------- Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com> Co-authored-by: Andrew Lock <andrewlock.net@gmail.com>
- Add frozen API contract comment to CalculateTracePipeName and
CalculateDogStatsDPipeName: assembly, type, method, version range,
and consequence of renaming (silent no-op in native profiler)
- Add reflection-based contract tests that catch renames at compile
time (nameof) and signature/accessibility changes at runtime
- Remove dead Environment.SetEnvironmentVariable("DD_TRACE_PIPE_NAME")
— nothing reads it; trace pipe flows tracer → DD_APM_WINDOWS_PIPE_NAME
→ mini-agent; only DD_DOGSTATSD_PIPE_NAME has an in-process consumer
- Drop unreachable null-check on Calculate* return values (both return string)
- Update existing ConfigureNamedPipes tests to assert DD_TRACE_PIPE_NAME
is NOT set, with explanatory comments
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
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…tName param CalculatePipeName was only ever called after DeterminePipeBaseName already confirmed no env var is set, so its internal DeterminePipeBaseName call always returned the hardcoded default. Inline the GUID generation directly into CalculateTracePipeName and CalculateDogStatsDPipeName and delete the now-dead helper. With no remaining callers passing a non-null default, drop the defaultName parameter from DeterminePipeBaseName entirely. Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
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Motivation
Improve support for running multiple Azure Functions in the same hosting plan. [jira]
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