http-server

Example HTTP Server

This directory contains a docker compose setup for a system consisting of three HTTP services and a Datadog Agent.

The "server" service is a note-taking app written in C++. Its source code is is in the server/ directory. See server/server.cpp. It uses a modified version of cpp-httplib to accept and make HTTP requests.

A reverse proxy sits in front of the server, and the reverse proxy is exposed to the host by binding to port 8000.

The note-taking app provides the following endpoints:

• GET /notes
  • Return application/json containing an array of notes, where each notes is an array containing the note's creation time and body text. For example, [["2023-05-12 16:18:37","here is another note"],["2023-05-12 15:06:10","this is my note"]].
• POST /notes
  • Insert the request body into the database as a new note.
• GET /sleep?seconds=[duration]
  • Wait for the specified [duration] number of seconds before responding.

The bin/http-server-example script builds the three services, starts them, and begins tailing their logs. The "server" build uses a GitHub release of dd-trace-cpp, rather than using the current source tree. bin/http-server-example requires a Datadog API key via the DD_API_KEY environment variable.

Once the services are started, requests can be made to 127.0.0.1:8000. Traces will appear in the Datadog UI. The docker compose services have the following Datadog service names:

docker compose service name	Datadog service name
proxy	dd-trace-cpp-http-server-example-proxy
server	dd-trace-cpp-http-server-example-server
database	dd-trace-cpp-http-server-example-database

Example Usage

In one command shell, run bin/http-server-example to bring up the services.

Then, in another command shell, use curl to read and write some notes.

Finally, open the Datadog UI in a web browser and navigate to APM > Traces. Search for service names matching dd-trace-cpp-http-server-example-*.

Click one of the results to display a flame graph of the associated trace.

At the top is the C++ proxy that we called using curl. Below that is the C++ server to which the proxy forwarded our request. Below that is the Python database service, including a span indicating its use of SQLite.