Is it worthwhile using IMAP COMPRESS (DEFLATE)?

Question

Gmail supports the IMAP COMPRESS Extension (RFC4978), specifically the DEFLATE algorithm (RFC1951) aka zlib/gzip.

I'm not normally a Python programmer but I threw a quick test script together using Piers Lauder's imaplib2 to determine performance with or without compression enabled.

from time import time
import imaplib2, string

def cb((response, cb_arg, error)):
        typ, data = response
        #print 'Message %s\n%s\n' % (cb_arg, data[0][5])

IMAP_SERVER='imap.gmail.com'
IMAP_PORT=993
IMAP_USERNAME='*********'
IMAP_PASSWORD='*********'

def gogmail(compress):
    start = time()
    M = imaplib2.IMAP4_SSL(IMAP_SERVER, IMAP_PORT, debug=0)
    M.login(IMAP_USERNAME, IMAP_PASSWORD)
    if(compress):
        M.enable_compression()
    M.SELECT(readonly=True)
    typ, data = M.SEARCH(None, 'ALL')
    fetch_list = string.split(data[0])[-100:]
    for num in fetch_list:
        M.FETCH(num, '(RFC822)', callback=cb, cb_arg=num)   
    M.LOGOUT()
    end = time()
    print end - start

print 'Compressed  '
print '------------'

for x in range(0, 50):
    gogmail(1)

print 'Uncompressed'
print '------------'

for x in range(0, 50):
    gogmail(0)

If I have made a glaring newbie error in my Python code please correct me.

I've run this test script a couple of times. Sometimes the mean average of compressed accesses is faster, sometimes not. There is never very much difference in mean average and a great deal of variation in access times (a single inbox access of 100 messages can take anywhere between 4 and 17 seconds). Consistent results would make my decision easier! Access is via SSL I was thinking that maybe there is some inherent compression in that (I don't know).

Do you think it is worthwhile using compression when accessing Gmail IMAP?

Incidentally, I would like to use JavaMail (rather than Python) but I understand I would need to customise JavaMail significantly to support compression (maybe using Jessie). Has somebody done this already? Would it be worthwhile?

I appreciate the feedback. Many Thanks.

Answer 1

I don't think enabling compression will make a great difference, simply because 100 messages is a tiny amount of data. Suppose one message is 1KB (a long plaintext message), so that your inbox is 100KB. Let's assume a compression ratio of 5:1 (which is unlikely at best), so that the compressed download is now 20KB.

Any sane internet connection these days runs at least at 1Mbps, or 125KB/s. So under these way-overestimated assumptions, you'd save somewhere under a second of data transmission costs. This is being dwarfed by the connection lag and the processing on gmail's side.

On the other hand, what do you lose by enabling compression?