Postgres Open Telemetry Extension

The pgotel project is a Postgres extension that allows other extensions to export observability signals (metrics, traces, logs, etc) with Open Telemetry. pgotel includes and exposes in a more Postgres-way (and in plain C, not C++) the Open Telemetry C++ SDK.

Protocol considerations

The OpenTelemetry Protocol (OTLP in short) defines two possible transports: gRPC and HTTP (supporting both 1.1 and 2.0 for the latter). The HTTP transport was added to OTLP after the gRPC transport with one of the main motivations being that "gRPC is a relatively big dependency, which some clients are not willing to take. Plain HTTP is a smaller dependency and is built in the standard libraries of many programming languages" (source). For this reason, only the HTTP transport has been chosen to be implemented into this extension.

Build and Install dependencies

# Install gRPC
git clone --recurse-submodules -b v1.62.0 https://github.com/grpc/grpc
cd grpc
mkdir -p cmake/build
pushd cmake/build
cmake -DgRPC_INSTALL=ON \
    -DgRPC_BUILD_TESTS=OFF \
    -DCMAKE_INSTALL_PREFIX=/usr/local \
    -DBUILD_SHARED_LIBS=ON \
    -DCMAKE_CXX_STANDARD=17 \
    -DABSL_PROPAGATE_CXX_STD=ON \
    ../..
make -j6
sudo make install

# Install Abseil
popd
mkdir -p third_party/abseil-cpp/cmake/build
pushd third_party/abseil-cpp/cmake/build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local \
    -DCMAKE_POSITION_INDEPENDENT_CODE=TRUE \
    -DBUILD_SHARED_LIBS=ON \
    -DCMAKE_CXX_STANDARD=17 \
    -DABSL_CXX_STANDARD=17 \
    -DABSL_PROPAGATE_CXX_STD=ON \
    ../..
make -j6
sudo make install
popd

# Rebuild ldconfig cache
sudo ldconfig

# Install Opentelemetry C++ SDK
git clone --recursive https://github.com/open-telemetry/opentelemetry-cpp
cd opentelemetry-cpp
mkdir -p build
pushd build
cmake -DBUILD_TESTING=OFF \
  -DWITH_OTLP_GRPC=ON \
  -DWITH_OTLP_HTTP=ON \
  -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
  -DCMAKE_CXX_STANDARD=17 \
  -DWITH_ABSEIL=ON \
  -DBUILD_SHARED_LIBS=ON ..
make -j6
sudo make install
popd

# Rebuild ldconfig cache
sudo ldconfig

Build Extension

make USE_PGXS=1
make USE_PGXS=1 install

Run OTEL collector

cd opentelemetry-cpp
## follow the instructions from here: https://github.com/open-telemetry/opentelemetry-cpp/tree/main/examples/otlp

Test extension

For now we have just one function named pgotel that send a trace to OpenTelemetry collector.

CREATE EXTENSION pgotel;
SELECT pgotel_counter('localhost:4317', 'counter_name', 10);