Monthly Archives: December 2016

percentile apache server request response times

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I needed a hack to quickly find the 95th percentile of apache request response times. For example I needed to be able to say that “95% of our apache requests are served in X milliseconds or less.” In the apache2 config the LogFormat directive had %D (the time taken to serve the request, in microseconds) as the last field. Meaning the last field of each log line would be the time it took to serve the request. This would make it easy to pull out with $NF in awk

# PCT=.95; NR=`cat access.log | wc -l `; cat /var/log/apache2/access.log | awk '{print $NF}' | sort -rn | tail -n+$(echo "$NR-($NR*$PCT)" |bc | cut -d. -f1) |head -1
938247

In this case 95% of the apache requests were served in 938 milliseconds or less (WTF?!). Then run on an aggregated group of logs, or change the date/time range to just run for logs on a particular day, or for multiple time periods.

Note: I couldn’t get scale to work here in bc for some reason.

wget use gzip header to received compressed output

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This test endpoint returns Content-Type: application/json

Without gzip enabled header:

$ wget -qO test https://testendpoint
$ file test
test: ASCII text, with very long lines, with no line terminators
$ du -b test
7307    test

Setting the gzip enabled header:

$ wget --header="accept-encoding: gzip" -qO test.gz https://testendpoint
$ file test.gz
test.gz: gzip compressed data, from Unix
$ du -b test.gz
1694    test.gz

Telling the server that wget can accept gzip compressed content results in 77% reduction in bytes transferred.