Compressing reports? - ooni-dev

19 Mar 2016


      I just downloaded all the http_requests reports from
https://measurements.ooni.torproject.org/. It took quite a long time and
I wonder if we can make things more efficient by compressing the reports
on the server.
This is the command I ran to download the reports:
    wget -c -r -l 2 -np --no-directories -A '*http_requests*' --no-http-keep-alive https://measurements.ooni.torproject.org/
This resulted in 309 GB and 6387 files.
If I compress the files with xz,
    xz -v *.json
they only take up 29 GB (9%).
Processing xz-compressed files is pretty easy, as long as you don't have
to seek. Just do something like this:
    def open_xz(filename):
        p = subprocess.Popen(["xz", "-dc", filename], stdout=subprocess.PIPE, bufsize=-1)
        return p.stdout
for line in open_xz("report.json"):
        doc = json.loads(line)
        ...
Of course you can do the same thing with gzip.