Handle ServerNotAvailableException in CollectLinuxCommand process probing by Copilot · Pull Request #5705 · dotnet/diagnostics

Copilot · 2026-02-05T18:51:02Z

Summary

Handle ServerNotAvailableException and DiagnosticToolException inCollectLinuxCommand process probing to gracefully handle processes that cannot be resolved or connected to.

Fixes #5694

Problem

DiagnosticsClient.GetProcessInfo() throws ServerNotAvailableException when the diagnostics server is unavailable (process exits between enumeration and probing, connection failures, etc.). Additionally, CommandUtils.ResolveProcess() throws DiagnosticToolException for invalid process IDs or names. These unhandled exceptions caused probe operations to crash.

Solution

Introduce a four-state probe result to handle all outcomes:

Supported: Process supports UserEvents IPC command
NotSupported: Process does not support UserEvents IPC command (runtime too old)
ProcessNotFound: Process could not be resolved (invalid PID, no process with given
name)
ConnectionFailed: Process resolved but unable to connect to diagnostic endpoint

Behavior Changes

Non-probe mode (dotnet-trace collect-linux -p <pid>):

ProcessNotFound: [ERROR] Could not resolve process '<id>'.
ConnectionFailed: [ERROR] Unable to connect to process '<id>'. The process may have exited or its diagnostic endpoint is not accessible.
Both return TracingError

Single-process probe mode (dotnet-trace collect-linux --probe -p <pid>):

ProcessNotFound: Could not resolve process '<id>'.
ConnectionFailed: Process '<id>' could not be probed. Unable to connect to the process's diagnostic endpoint.
Returns Ok (informational output)

Machine-wide probe mode (dotnet-trace collect-linux --probe):

Shows "Processes that could not be probed" section when applicable
CSV output includes unknown value for unprobed processes
Processes that exit between enumeration and probing are handled gracefully

Other Changes

Added FormatProcessIdentifier helper - shows name (pid) when name is provided, just pid otherwise
Changed ".NET process" to "Process" in messages (probe accepts arbitrary PIDs)
Updated --probe option help text to document result categories

…lpers Add UserEventsProbeResult enum (Supported/NotSupported) to replace boolean return. Introduce ProbeProcess helper for probing a single process. Add GetAndProbeAllProcesses helper that enumerates and probes all published processes. Update callers in CollectLinux and SupportsCollectLinux to use new helpers. Update BuildProcessSupportCsv to use UserEventsProbeResult enum.

…cess probing Add ProcessNotFound and ConnectionFailed values to UserEventsProbeResult enum. Update ProbeProcess to catch DiagnosticToolException (process resolution failed) and ServerNotAvailableException (diagnostic endpoint not accessible) separately. Add FormatProcessIdentifier helper for clean display of process ID/name. Add unknownProcesses/unknownCsv tracking for processes that could not be probed. Update probe mode output to show 'Processes that could not be probed' section. Include 'unknown' value in CSV output for unprobed processes. Update non-probe mode to show distinct errors for each failure type. Change '.NET process' to 'Process' in messages since arbitrary PIDs may not be .NET. Fixes #5694

Document that results are categorized as supported, not supported, or unknown. Clarify that unknown status occurs when diagnostic endpoint is not accessible.

…iled handling Update test expectations to match new behavior: - Add FormatProcessNotFoundError and FormatProcessIdentifier helpers - Update ResolveProcessExceptions test data for ProcessNotFound handling - Update probe error test cases for process resolution errors - Tests now expect ReturnCode.TracingError for failures in non-probe mode - Tests expect ReturnCode.Ok for probe mode with informational output

Copilot

Pull request overview

This PR improves dotnet-trace collect-linux resilience by handling process-resolution and diagnostics-connection failures during “process probing” so the command no longer crashes when a target process can’t be resolved or connected to (e.g., exits between enumeration and probing, cross-container endpoint issues).

Changes:

Replaced boolean “supports” probing with a 4-state probe result (Supported/NotSupported/ProcessNotFound/ConnectionFailed) and updated user-facing output.
Updated machine-wide probe to track and report “unknown/unprobed” processes and emit unknown in CSV.
Adjusted functional tests to match new probe behaviors/messages (partially—some existing expectations still appear outdated).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 8 comments.

File	Description
`src/Tools/dotnet-trace/CommandLine/Commands/CollectLinuxCommand.cs`	Introduces multi-state probing, catches `DiagnosticToolException`/`ServerNotAvailableException`, updates probe messaging and CSV output.
`src/tests/dotnet-trace/CollectLinuxCommandFunctionalTests.cs`	Updates/extends tests for new probe outcomes and adds helpers for the new process identifier/message formatting.

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src/Tools/dotnet-trace/CommandLine/Commands/CollectLinuxCommand.cs

src/tests/dotnet-trace/CollectLinuxCommandFunctionalTests.cs

src/Tools/dotnet-trace/CommandLine/Commands/CollectLinuxCommand.cs

src/tests/dotnet-trace/CollectLinuxCommandFunctionalTests.cs

…-diagnostics-client-exception

…codes Per review feedback, single-process paths (explicit -p PID or -n NAME) now call CommandUtils.ResolveProcess separately so argument validation errors propagate with original specific messages and ArgumentError return code. ProbeProcess is only used for the resolved PID's runtime check and connection attempt. Restore '.NET process(es)' wording in probe output messages. Remove unused FormatProcessIdentifier helper from both source and tests. Revert probe error tests to expect ArgumentError with original messages. Revert ResolveProcessExceptions test data to original error text. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The supportedCsv, unsupportedCsv, and unknownCsv variables are always non-null when the CsvToConsole and Csv output blocks are reached, since generateCsv is true for those modes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/tests/dotnet-trace/CollectLinuxCommandFunctionalTests.cs

src/Tools/dotnet-trace/CommandLine/Commands/CollectLinuxCommand.cs

Update connection failure messages per review: use 'diagnostic port' instead of 'diagnostic endpoint', and reword to indicate the process may not have a .NET diagnostic port rather than implying it exists but is inaccessible. Skip processes that exit during name resolution silently rather than reporting them as unknown, per reviewer suggestion that users wouldn't find it surprising. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI assigned Copilot and mdh1418 Feb 5, 2026

Copilot started work on behalf of mdh1418 February 5, 2026 18:51 View session

Copilot AI changed the title ~~[WIP] Investigate DiagnosticsClient.GetProcessInfo exception~~ Handle ServerNotAvailableException in CollectLinuxCommand process probing Feb 5, 2026

Copilot AI requested a review from mdh1418 February 5, 2026 19:03

Copilot finished work on behalf of mdh1418 February 5, 2026 19:03

mdh1418 force-pushed the copilot/fix-diagnostics-client-exception branch from 8fe26f7 to fe76ee6 Compare February 6, 2026 17:21

mdh1418 added 4 commits February 6, 2026 19:20

Update --probe option help text

6f420b2

Document that results are categorized as supported, not supported, or unknown. Clarify that unknown status occurs when diagnostic endpoint is not accessible.

mdh1418 force-pushed the copilot/fix-diagnostics-client-exception branch from fe76ee6 to 0cbcf44 Compare February 6, 2026 19:54

mdh1418 marked this pull request as ready for review February 6, 2026 20:02

mdh1418 requested a review from a team as a code owner February 6, 2026 20:02

mdh1418 requested review from Copilot, hoyosjs, lateralusX and noahfalk February 6, 2026 20:02

Copilot started reviewing on behalf of mdh1418 February 6, 2026 20:02 View session

Copilot AI reviewed Feb 6, 2026

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noahfalk reviewed Feb 6, 2026

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mdh1418 and others added 3 commits March 6, 2026 18:38

Merge branch 'main' of https://github.com/dotnet/diagnostics into fix…

bb96bfc

…-diagnostics-client-exception

noahfalk reviewed Mar 7, 2026

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src/tests/dotnet-trace/CollectLinuxCommandFunctionalTests.cs Outdated Show resolved Hide resolved

src/Tools/dotnet-trace/CommandLine/Commands/CollectLinuxCommand.cs Outdated Show resolved Hide resolved

mdh1418 and others added 2 commits March 9, 2026 23:43

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Handle ServerNotAvailableException in CollectLinuxCommand process probing#5705

Handle ServerNotAvailableException in CollectLinuxCommand process probing#5705
Copilot wants to merge 9 commits intomainfrom
copilot/fix-diagnostics-client-exception

Copilot AI commented Feb 5, 2026 •

edited by mdh1418

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Copilot AI commented Feb 5, 2026 •

edited by mdh1418

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