The sys admin's daily grind – httpstat

My Point of View

Article from Issue 195/2017
Author(s):

Httpstat is a special stopwatch you can use to discover how long web servers take to serve up a static or dynamic HTML page. Visible performance lags indicate optimization potential for the server.

Httpstat is a Python script that wraps itself around cURL. Apart from Python 2 or 3 and cURL, it has no other dependencies. You can retrieve it from the GitHub repository and call it using:

wget https://raw.githubusercontent.com/reorx/httpstat/master/httpstat.py
python httpstat.py <URL>

If the Python installer pip is present on your system, you also can pick up the script and call it with:

pip install httpstat
httpstat <URL>

Although you can leave an http:// out of the URL, you cannot omit https:// for web pages secured with TLS.

Figure 1 shows httpstat measuring an unencrypted call. Four milliseconds for a DNS reply is a really good value, but I cheated: The name of the site is cached on my local Dnsmasq. As soon as my computer has to turn to my provider's DNS, the value rises to 80-200ms. The TCP handshake is 22ms, which is about par for the course.

Figure 1: The page that httpstat requests via HTTP, and receives quickly, is only an error message in reality.

The time the server needs to create the page (Server Processing) shows whether the web server has some tuning potential that I have not tapped. My example is not representative, because instead of HTML, the server simply outputs 301 Moved Permanently, which means I should have called the page using HTTPS. A browser would do that independently, but not cURL.

Figure 2 requests the same page using HTTPS. The lookup and TCP values remain the same, but the TLS Handshake takes forever for this static page. The value can go up to several seconds for a big site with a large volume of dynamic content and advertising banners.

Figure 2: When requested using HTTPS, the HTML page obviously takes longer to appear.

Httpstat is not controllable using command-line parameters because they would be fielded by cURL; however, you can influence the tool with environment variables. The line

export HTTPSTAT_SHOW_SPEED=true

tells httpstat to show how quickly the web page is delivered (e.g., speed_download: 219.6 KiB/s, speed_upload: 0.0 KiB/s). The httpstat website [1] explains all of the variables and has links to the httpstat implementation in Go, Bash, and PHP.

The Author

Charly Kühnast manages Unix systems in the data center in the Lower Rhine region of Germany. His responsibilities include ensuring the security and availability of firewalls and the DMZ.

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