ZeroTierOne/ext/opentelemetry-cpp-1.21.0/docs/dependencies.md

Dependencies and Licenses

There are

• External dependencies as linkable libraries or externally installed headers, and
• Internal dependencies as the part of code from external libraries backported/copied in main repo.

Both these dependencies are listed here:

Internal dependencies

• nostd::variant: This is backported from Abseil C++ libraries and used as default variant implementation. License: Apache License 2.0
• TraceLoggingDynamic: Dynamic TraceLogging Provider API for C++ used by ETW exporter. License: MIT License

External dependencies

• API & SDK:

  • Uses Standard C++ library for latest features (std::string_view, std::variant, std::span, std::shared_ptr, std::unique_ptr) with C++14/17/20 compiler if cmake option WITH_STL is enabled or macro OPENTELEMETRY_STL_VERSION is defined. License: GNU General Public License
    • For C++14/17 compilers, fallback to gsl::span if GSL C++ library is installed. License: MIT License
    • libc++ 14.0.0 do not support construct std::span from a range or container .We don't use the std::span in this situation.Users can also define OPENTELEMETRY_OPTION_USE_STD_SPAN=0 to indicate nostd:span will always not be a alias for std::span.

• OTLP/HTTP+JSON exporter:

  • protobuf: Library to serialize structured data.
    • OTLP messages are constructed as protobuf payloads.
    • protoc compiler is used to generate C++ stubs for proto files provided by opentelemetry-proto.
    • libprotobuf library is used for generating serialized trace/metrics/log data to be sent to opentelemetry collector.
    • License: The library is licensed here. The code generated by protoc compiler is owned by the owner of .proto file.
  • libcurl : the multiprotocol file transfer library.
    • Export connects with opentelemetry collector over HTTP protocol using libcurl library
    • License: Inspired by MIT/X but not same. https://curl.se/docs/copyright.html
  • nlohmann/json: JSON for Modern C++.
    • protobuf serialized otlp messages are encoded in JSON format using this library.
    • License: MIT License
  • zlib: A Massively Spiffy Yet Delicately Unobtrusive Compression Library.
    • The http_client utilizes zlib to compress the message body and send it in gzip format.
    • License: The library is licensed here

• OTLP/gRPC exporter:

  • protobuf OTLP messages are constructed as protobuf payloads.
  • gRPC: An RPC library and framework
    • Exporter communicates with OTLP collector using gRPC transport mechanism.
    • License: Apache License 2.0

• Zipkin exporter:

  • libcurl for connecting with Zipkin server over HTTP protocol.
  • nlohmann/json for encoding Zipkin messages.

• ETW exporter:

  • nlohmann/json for generating MessagePack serialization for message to be transmitted to ETW.

• Prometheus exporter:

  • prometheus-cpp Prometheus Client Library for Modern C++
    • License: MIT License

• ElasticSearch exporter:

  • libcurl for connecting with Elasticsearch server over HTTP protocol.
  • nlohmann/json for encoding Elastic Search messages.

• Opentracing shim:

  • opentracing-cpp OpenTracing API for C++
    • A bridge layer implementing the OpenTracing API using the OpenTelemetry API
    • License: Apache License 2.0