A small webapp for generating Server-Timing headers
The Server-Timing specification is a way to add semi-structured values
describing aspects of the response generation and how long each section
took to a HTTP request. These can then be processed and displayed in
your normal web development tools. This small flask application provides
a simple way to specify values for the Server-Timing header. It was written to
help provide a canned data source for some of my other projects.
You can learn more about the general usage of the header in my Show server side response timings in chrome developer tools post.
I run all my python projects under venvs so the instructions below reflect
this:
git clone https://github.com/deanwilson/server-timing-header-tester.git
cd server-timing-header-tester
# create the venv and activate it
python3 -mvenv venv
source venv/bin/activate
# install the dependencies
pip3 install -r requirements.txt
Now we've done all the preparation work we can run the application.
FLASK_APP=stt flask run
curl -I http://127.0.0.1:5000/
Server-Timing: MISSED, database;dur=123, cache;dur=10;desc=cache_check
By default stt (Server-Timing Tester) returns a header with one of each type
of value. A base name, MISSED, a value with a duration, database and one
with both a duration and a description, cache.
To specify your own values you need to pass parameters named timing to
the application.
# A single value
curl -I 127.0.0.1:5000?timing='mysql;dur=200;desc=databasequery'
# multiple values
curl -I 127.0.0.1:5000?timing='mysql;dur=200;desc=databasequery&timing=crm;dur=400'
These values from these parameters will be reflected in the Server-Timing header. One additional use case is the ability to specify a range in the duration:
curl -I 127.0.0.1:5000?timing='mysql;dur=200..400;desc=databasequery'
...
Server: Flask Server Timing header test
Server-Timing: mysql;desc=databasequery;dur=319
...
Specifying a lower and upper boundary in this format, dur=200..400, will cause
the application to replace it with a random value from inside the range. This
allows a small amount of dynamic behaviour when running the same request
repeatedly (and makes the graphs more interesting).
It's worth noting that you can pass the parameters to the application via a web browser too. This allows you to view them in your normal web developer tools.
This application provides basic tests to ensure its behaviour is correct. They are located in /tests/ and run under pytest.
python3 -m pytest -v tests/
tests/test_defaults.py::test_default_index PASSED [ 20%]
tests/test_defaults.py::test_default_headers PASSED [ 40%]
tests/test_defaults.py::test_single_url_param PASSED [ 60%]
tests/test_defaults.py::test_multiple_url_params PASSED [ 80%]
tests/test_defaults.py::test_random_number_url_param PASSED [100%]