OTLP exporter v1.22.0 - Resulting deployment is not correct

[gparlamas]

Describe your environment

RH 8.10

Installed everything from source for OTLP sdk/exporters only

ci/install_thirdparty.sh --install-dir /home/gp/usr/local/otelLibs --tags-file install/cmake/third_party_latest --packages "abseil;ms-gsl;zlib;protobuf;grpc;ms-gsl;opentelemetry-proto"

For otel build

cmake -DCMAKE_INSTALL_PREFIX=/home/gp/usr/local/otel ..

-- gRPC_CPP_PLUGIN_EXECUTABLE=$<TARGET_FILE:gRPC::grpc_cpp_plugin>
-- PROTOBUF_PROTOC_EXECUTABLE=$<TARGET_FILE:protobuf::protoc>

---

-- build settings

---

-- OpenTelemetry: 1.22.0
-- OpenTelemetry ABI: 2
-- CMAKE_SYSTEM_PROCESSOR: x86_64
-- CXX: GNU 8.5.0
-- CMAKE_BUILD_TYPE: Release
-- CXXFLAGS:
-- CMAKE_CXX_STANDARD: 17
-- CMAKE_TOOLCHAIN_FILE:
-- BUILD_SHARED_LIBS:

---

-- opentelemetry-cpp build options

---

-- WITH_API_ONLY: OFF
-- WITH_NO_DEPRECATED_CODE: ON
-- WITH_ABI_VERSION_1: OFF
-- WITH_ABI_VERSION_2: ON
-- OTELCPP_VERSIONED_LIBS: OFF
-- OTELCPP_MAINTAINER_MODE: OFF
-- WITH_STL: CXX17
-- WITH_GSL: OFF
-- WITH_NO_GETENV: OFF

---

-- opentelemetry-cpp cmake component options

---

-- WITH_OTLP_GRPC: ON
-- WITH_OTLP_HTTP: OFF
-- WITH_OTLP_FILE: OFF
-- WITH_HTTP_CLIENT_CURL: OFF
-- WITH_ZIPKIN: OFF
-- WITH_PROMETHEUS: OFF
-- WITH_ELASTICSEARCH: OFF
-- WITH_OPENTRACING: OFF
-- WITH_ETW:
-- OPENTELEMETRY_BUILD_DLL:

---

-- feature preview options

---

-- WITH_ASYNC_EXPORT_PREVIEW: ON
-- WITH_THREAD_INSTRUMENTATION_PREVIEW: ON
-- WITH_METRICS_EXEMPLAR_PREVIEW: ON
-- WITH_OTLP_GRPC_SSL_MTLS_PREVIEW: ON
-- WITH_OTLP_GRPC_CREDENTIAL_PREVIEW: ON
-- WITH_OTLP_RETRY_PREVIEW: ON

---

-- third-party options

---

-- WITH_NLOHMANN_JSON: OFF
-- WITH_CURL_LOGGING: OFF
-- WITH_OTLP_HTTP_COMPRESSION: OFF

---

-- examples and test options

---

-- WITH_BENCHMARK: OFF
-- WITH_EXAMPLES: ON
-- WITH_EXAMPLES_HTTP: OFF
-- WITH_FUNC_TESTS: OFF
-- BUILD_W3CTRACECONTEXT_TEST: OFF
-- BUILD_TESTING: OFF

---

-- versions

---

-- CMake: 3.26.5
-- GTest: ()
-- benchmark: ()
-- Abseil: 20240722
-- opentelemetry-proto: 1.7.0 (fetch_repository)
-- Protobuf: 30.2.0 (find_package - STATIC_LIBRARY)
-- gRPC: 1.72.1 (find_package - STATIC_LIBRARY)
-- ZLIB: 1.2.11 ()

Build & deployment succeeds.

What is the expected behavior?

"make install" will deploy all needed artefacts.

Setting the below in my CMakeList.txt to be sufficient

list(APPEND CMAKE_PREFIX_PATH "/home/gp/usr/local/otel/lib64/cmake/")
find_package(opentelemetry-cpp CONFIG REQUIRED)

What is the actual behavior?

CMake fails, it tries to find libraries I thought are only needed for the SDK building

-- get_installed_components: component = api, installed = TRUE
-- get_installed_components: component = sdk, installed = TRUE
-- get_installed_components: component = ext_common, installed = TRUE
-- get_installed_components: component = exporters_otlp_common, installed = TRUE
-- get_installed_components: component = exporters_otlp_grpc, installed = TRUE
-- get_installed_components: component = exporters_ostream, installed = TRUE
-- get_installed_components: component = exporters_in_memory, installed = TRUE
-- get_requested_components: Components requested: api;sdk;exporters_otlp_grpc
-- find_required_dependencies: dependency = Microsoft.GSL, is_required = FALSE
-- find_required_dependencies: dependency = ZLIB, is_required = FALSE
-- find_required_dependencies: dependency = CURL, is_required = FALSE
-- find_required_dependencies: dependency = nlohmann_json, is_required = FALSE
-- find_required_dependencies: dependency = Protobuf, is_required = TRUE
-- find_required_dependencies: calling find_dependency(Protobuf CONFIG )...

CMake Error at /usr/share/cmake/Modules/CMakeFindDependencyMacro.cmake:76 (find_package):
Could not find a package configuration file provided by "Protobuf" with any
of the following names:

ProtobufConfig.cmake
protobuf-config.cmake

Add the installation prefix of "Protobuf" to CMAKE_PREFIX_PATH or set
"Protobuf_DIR" to a directory containing one of the above files. If
"Protobuf" provides a separate development package or SDK, be sure it has
been installed.

Have I done something wrong or my expectation, the OTEL public API doesnt pull any third party dependency, is wrong?

[dbarker]

Hi @gparlamas, thanks for testing this and sharing the CMake logs.

From the command you shared the ci/install_thirdparty.sh script will install the dependencies (Protobuf, gRPC, ...) to /home/gp/usr/local/otelLibs and your CMake command will install opentelemetry-cpp to /home/gp/usr/local/otel. However, when you configure your project only the latter path is set to CMAKE_PREFIX_PATH.

Adding the install path of opentelemetry-cpp (/home/gp/usr/local/otel) and the install path of the dependencies (/home/gp/usr/local/otelLibs) to CMAKE_PREFIX_PATH should allow Protobuf to be found.

[gparlamas]

Hi @dbarker,

I am not using grpc / proto /absl in my system so would like to minimise 3rd party dependencies.
I thought / was hoping the static build of otlp libs will contain everything that's needed / pull all deps and link everything into static lib or "make install" will pull everything required.

If I use the same installation path for both, ci/install_thirdparty.sh deploys lots of libraries I don't need so will have to
manually start deleting stuff till the build breaks. Not ideal.

[gparlamas]

this is how it looks if path is the same

ls /home/gp/usr/local/include/
absl ares_dns.h ares_nameser.h ares_version.h grpc grpcpp opentelemetry upb utf8_validity.h zlib.h
ares_build.h ares.h ares_rules.h google grpc++ gsl re2 utf8_range.h zconf.h

ls /home/gp/usr/local/lib/
cmake libgpr.a libgrpc_authorization_provider.a libgrpc++_reflection.a libssl.a libupb_message_lib.a libutf8_range_lib.a libz.so.1.3.1
libaddress_sorting.a libgrpc++.a libgrpc++_error_details.a libgrpc++_unsecure.a libupb_base_lib.a libupb_mini_descriptor_lib.a libz.a pkgconfig
libcares.a libgrpc.a libgrpc_plugin_support.a libgrpc_unsecure.a libupb_json_lib.a libupb_textformat_lib.a libz.so
libcrypto.a libgrpc++_alts.a libgrpcpp_channelz.a libre2.a libupb_mem_lib.a libupb_wire_lib.a libz.so.1

ls /home/gp/usr/local/lib64/

Not showing lib64, too many libs

From include dir above I only need opentelemetry folder for my app

[dbarker]

@gparlamas Thanks for the context. From your original CMake logs WITH_OTLP_GRPC=ON which will build the otlp grpc exporters (requiring Abseil, Protobuf, zlib and gRPC). Protobuf will be a public transitive dependency from opentelemetry-cpp to your project, while gRPC is private to opentelemetry-cpp. CMake therefore needs to find both (and these have a transitive dependency on abseil and zlib).

When you call find_package(opentelemetry-cpp CONFIG) it will call find_dependency(Protobuf CONFIG) and find_dependency(gRPC CONFIG) implicitly because CMake needs to know how to find these dependencies (public or private) - this is a consequence of opentelemetry-cpp's CMake calling target_link_libraries on Protobuf and gRPC targets without restricting to just the BUILD_INTERFACE.

There is some room for cleanup in your commands. Since you are not setting WITH_GSL=ON you can remove ms-gsl from the install and allow opentelemetry-proto to be fetched from GitHub.

This should work for your setup:

ci/install_thirdparty.sh --install-dir /home/gp/usr/local/otelLibs --tags-file install/cmake/third_party_latest --packages "abseil;zlib;protobuf;grpc;"

[gparlamas]

Thanks @dbarker
It's not ideal though for systems that are not using directly these 3, big, libraries (absl, proto, grpc).
Otel is forcing us to deploy them.

I noticed as well by looking at build.make/link.txt files cmake generates for a target that uses otlp
that the target depends on pretty much every library I manually build, ~107 in total!
libabsl_* /libupb_* /libgrpc.a/libprotobuf.a/libgrpc++.a/libopentelemetry_* etc

[marcalff]

@gparlamas

Can you clarify which exporter the application will use precisely ?
The build shows WITH_OTLP_GRPC=ON, is this intended ?

[gparlamas]

Hi @marcalff

I am using / exporting metrics only using otlp protocol over grpc.
Using
find_package(opentelemetry-cpp CONFIG REQUIRED COMPONENTS api exporters_otlp_grpc)

I am building a mini lib with
target_link_libraries(otel-lib PUBLIC opentelemetry-cpp::api PRIVATE opentelemetry-cpp::otlp_grpc_metrics_exporter)

and apps link against it

target_link_libraries(myApp PUBLIC otel-lib)

I chose otlp-grpc for performance reasons / control, binary protocol / can pin exporter thread with opentelemetry::sdk::common::ThreadInstrumentation::OnStart()

Prometheus, which I have build too, its quite small library so none of the above worries apply.
Unfortunately Its a text protocol and I don't understand its threading model - which thread runs the web server / can I control it?

[marcalff]

@gparlamas

Thanks for the details.

If using the OTLP GRPC exporter, then yes, this will bring a lot of dependencies due to grpc.

I don't have performance numbers to compare, but note that the OTLP HTTP exporter can send binary as well, with protobuf encoding.

[gparlamas]

@marcalff Indeed, otlp-http doesn't rely on gRPC, deploying OpenTelemetry dependencies is significantly less noisy and more lightweight.