urllib3 testrun

This is a simple test/benchmark I wrote to test out the new urllib3 library that I found on the internets today. I currently use the excellent httplib2, so I used it for comparison.

A typical run looks something like this:

simple sequential download, first run:

urllib3  took 2.396 seconds
httplib2 took 1.851 seconds

simple sequential download, second run:

urllib3  took 1.705 seconds
httplib2 took 0.104 seconds

now, urllib3 with 4 threads and 4 connections:

took 1.124 seconds

Each timed run downloads 15 URLs, all from the same google domain.

In the first sequential benchmark, httplib2 and urllib3 are pretty even. Sometimes one is faster, sometimes the other is. It's a wash. This makes sense because they both have persistent connections.

In the second sequential benchmark, httplib2 is always much faster, due to it pulling everything from its on-disk cache.

In the last benchmark, urllib3 tends to execute in 1/3 to 1/2 the time it would sequentially, by using a thread pool and a connection pool, each with a size of 4. There is no comparison with httplib2 here, because httplib2 currently is not thread-safe.


  • urllib3 is no faster than httplib2 if used in a sychronous, sequential manner, even if fetching from the same domain over and over.
  • httplib2 is incredibly faster than urllib3 if you are fetching the same content over and over and can take advantage of caching.
  • urllib3 is much faster than httplib2 if you run multiple threads, which httplib2 is currently not capable of. This is urllib3's killer feature.
  • The speed benefits from caching vs. multi-threaded downloading may be hard to accurately predict, and it's not trivial to swap out one library for the other to do a test run (see next item).
  • urllib3 is a bit more primitive in its API, forcing you to create a separate HTTPConnectionPool object for every domain you want to connect to. You might want to construct a "pool of pools" which would transparently cache these pool objects, expiring ones that haven't been used in a while, or something similar. httplib2 already does this for you.

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Nick Welch <> · github · twitter