Datadog Nginx Tracing Module

This is the source for an nginx module that adds Datadog distributed tracing to nginx. The module is called ngx_http_datadog_module.

Usage

1. Download a gzipped tarball from a recent release, extract it to wherever nginx looks for modules (e.g. /usr/lib/nginx/modules/).
2. Add the following line to the top of the main nginx configuration (e.g. /etc/nginx/nginx.conf):

load_module modules/ngx_http_datadog_module.so;

Tracing is automatically added to all endpoints by default. For more information, see the API documentation.

Compatibility

Important

We provide support for NGINX versions up to their End Of Life, extended by one year. Aligned with the NGINX release cycle, this entails support for the four most recent NGINX versions.

If you plan to add tracing features to an older NGINX version using our module, please check out the build section for guidance.

There is one version of the module for each docker image we follow, which include the following:

• Debian variants of nginx's DockerHub images.
• Alpine variants of nginx's DockerHub images.
• Amazon Linux.

Each release contains one zipped tarball per supported image above. The zipped tarball contains a single file, ngx_http_datadog_module.so, which is the Datadog tracing nginx module.

The naming convention is <base image with underscores>-<arch>-ngx_http_datadog_module.so.tgz.

Supported architectures (<arch>) are amd64 and arm64.

Examples:

• nginx_1.23.1-alpine-amd64-ngx_http_datadog_module.so.tgz corresponds to NGINX version 1.23.1 docker image, running on Alpine, and designed for the amd64 architecture.
• amazonlinux_2.0.20230119.1-arm64-ngx_http_datadog_module.so.tgz refers to Amazon Linux version 2.0.20230119.1 docker image, designed for the arm64 architecture.

Default Behavior

Unless otherwise configured, ngx_http_datadog_module adds the following default tracing behavior to nginx:

• Connect to the Datadog agent at http://localhost:8126.
• Create one span per request:
  • Service name is "nginx".
  • Operation name is "nginx.request".
  • Resource name is "$request_method $uri", e.g. "GET /api/book/0-345-24223-8/title".
  • Includes multiple http.* tags.

Custom configuration can be specified via the datadog_* family of directives in nginx's configuration file, or via environment variables.

Build

Requirements:

• C and C++ toolchain (clang or gcc/g++).
• CMake v3.7 or newer.
• Architecture must be x86_64 or arm64.

For enhanced usability, we provide a GNU make compatible Makefile.

NGINX_VERSION=1.25.2 make build

The resulting nginx module is .build/ngx_http_datadog_module.so

The build target does the following:

• Download a source release of nginx based on the NGINX_VERSION environment variable.
• Initialize the source tree of dd-trace-cpp as a git submodule.
• Build dd-trace-cpp and the Datadog nginx module together using CMake.

make clean deletes CMake's build directory. make clobber deletes everything done by the build.

Build in Docker

make build-in-docker

build-in-docker target, builds the Datadog nginx module and its dependencies in a Docker container compatible with the DockerHub image specified as BASE_IMAGE in the nginx-version-info file, (e.g. nginx:1.19.1-alpine) and with the nginx source version specified as NGINX_VERSION in the nginx-version-info file (e.g. 1.19.1).

The appropriate build image must be created first using the bin/docker_build.sh script if it does not exist already. Once the image is built, make build-in-docker produces the nginx module as .docker-build/ngx_http_datadog_module.so.

Test

See test/README.md.

Acknowledgements

This project is based largely on previous work. See CREDITS.md.