Introduction

Within the tracing and telemetry space there are many API or library choices and it's very difficult (if not impossible) to choose correctly. There is a general need for the ability to emit structured, cross platform events in high performance code paths.

Exclusively using existing encoders and tooling (e.g. ETW on Windows, LTTng on Linux) CLOG provides:

• Durable Identifiers for use in telemetry pipelines.
• Manifested events and argugments with type safety.
• Generates clear, human readable text for the final log format.
• The ability to use existing tooling, such as like WPA.

Claims

CLOG makes these claims:

1. Code and tool assets need to be decoupled from bit encoders to preserve the code/tools assets as bit encoders are modified (as would happen as code moves between OS's or projects) API abstractions not a sufficient solution to our problems, due to performance. Worse, API's tend to create permanent couplings between code and tools due to those couplings. Clog argues a tool (and not a library) best solves the range of problems we face.

2. Event description (manifests), for purposes of tooling needs to be decoupled from description for human presentation (text files). For example the Windows Performance Analyzer (WPA) have different needs as compared to a human reading a log.

CLOG holds these claims by:

• Using a printf-like syntax for event description:

  TraceLogWarning(
      DroppedPacket,
      "[conn][%p] DROP packet[%llu] Dst=%!ADDR! Src=%!ADDR! Reason=%s.",
      Connection,
      Packet->PacketNumber,
      CLOG_BYTEARRAY(sizeof(Datagram->LocalAddress), &Datagram->LocalAddress),
      CLOG_BYTEARRAY(sizeof(Datagram->RemoteAddress), &Datagram->RemoteAddress),
      Reason);

• Selecting a bit encoder based on build time tool parameters, not API configuration. In this way we're not adding yet another API surface within any OS:

  {
    "MacroName": "TraceLogWarning",
    "EncodedPrefix": null,
    "EncodedArgNumber": 1,
    "CustomSettings": {
      "WPPArgNumber": "0",
      "ETWManifestFile": "Component.man",
      "ETW_Provider": "440d0192-e016-49e9-8f9a-639f5b275ab0"
    },
    "CLogExportModules": [
      "MANIFESTED_ETW",
      "TRACELOGGING",
      "DTRACE"
    ]
  }

• Deferring the choice of event descriptions (manifest), for tooling. This maximizes utility of existing tooling (like WPA). The author chooses, at build time, how their events are manifested based on their needs – the decision can be reevaluated in the future without making changes to code or tools.

• Requiring a "side car" (external manifest) for event presentation to a human readable format (e.g. [conn][%p] DROP packet[%I] Dst=%!IPADDR! Src=%!IPADDR! Reason=%s. )

Tools and Modules

Note the .exe extension is provided for clarity, clog.exe is cross platform and on Linux the .exe will not be present.

Work flow

1. At build time, your source file will be read and processed using a config file. clog.exe produces .c and .h files that contains OS specific code.
2. Using your favorite OS collection mechanism, collect traces using the appropriate tools.
3. For debugging, convert your recorded traces into something human readable using one of the tools (e.g. clog2text_windows or clog2text_lttng).

Modules

• clog.exe

  Build time tool to generate source code based on regex parsing of C/C++ code. This is the main tool for clog.

• clog2text_lttng.exe

  LINUX ONLY : Combines CLOG events that are stored with LTTng into human readable text.

• clog2text_windows.exe

  WINDOWS ONLY : Combines CLOG events that are stored with ETW into human readable text.

• clogutils.dll

  Utility library used between clog.exe and other clog tools.

Supported Runtimes

The build .NET clog tools can be ran on .NET 6. In order to build, .NET 6 is required.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.