Make your code robust with Tillicum
Tillicum is a collection of utilities for instrumenting functions which talk to network services. It makes use of python-ostrich for metrics.
Backoff adds an increasing delay depending on the error rate of the wrapped function. This is useful when your remote service has periods of high latency, as it applies back pressure to your client(s) to let the service recover.
Backoff can be used as a decorator or a context manager.
from tillicum.backoff import backoff @backoff(exceptions=(socket.timeout, socket.error)) def talk(): remote = urllib2.urlopen('http://some.service:2351') return remote.read() # -> Will delay more based on error rate def talk(): with backoff(exceptions=(socket.timeout, socket.error)): remote = urllib2.urlopen('http://some.service:2351') return remote.read() # -> Will delay more based on error rate
Ratelimit will delay consumption of a sequence to something you specify.
from tillicum.ratelimit import ratelimit # Limited to 10/s, this function will take 10s to run def limit_seq(): for x in ratelimit(xrange(100), 10): print x
The retry decorator will restart a function if it raises one of a predefiend list of exceptions. This is good for talking to flaky services, where you would like to retry if it times out.
import urllib2 import socket from tillicum.retry import retry @retry(exceptions=(socket.timeout, socket.error)) def talk(): remote = urllib2.urlopen('http://some.service:2351') return remote.read() # -> Will retry up to 3 times
The seqtimer function is used to monitor and report the time taken during consumption of a sequence. If the length of the sequence can be determined (or you explicitly provide it), seqtimer will provide an estimated time to completion.
from tillicum.seqtimer import seqtimer def read_sequence(input): # Print summary every 100 items consumed. for element in seqtimer(input, items=100): do_something_with(element) # Sample output: # [1.00% 100/10000] 100 items in 0.11s @902.05/s; Avg @902.05/s, ETA 0:00:10 # [2.00% 200/10000] 100 items in 0.11s @910.81/s; Avg @906.18/s, ETA 0:00:10 # [3.00% 300/10000] 100 items in 0.11s @906.16/s; Avg @906.05/s, ETA 0:00:10 # [4.00% 400/10000] 100 items in 0.11s @897.70/s; Avg @903.86/s, ETA 0:00:10
Suppress creates a context manager which will ignore specific exceptions unless they exceed a specified error rate. It can be composed with the retry decorator, or used on its own for non-critical failure-prone operations.
import socket from tillicum.suppress import make_suppress from tillicum.retry import retry manager = make_suppress((socket.error, socket.timeout), interval=60, threshold=10) def talk(): @retry(3) def _internal(): remote = urllib2.urlopen('http://some.service:2351') return remote.read() with manager(): return _internal()
Throttle is used to slow down calls to functions by delaying by a factor of the time the function call took. It’s useful when you need to talk to a fragile service without overwhelming it with requests.
Throttle can be used as a decorator or context manager. It measures the time taken to execute the wrapped code, then delays by that time multipled by a factor before returning. Additionally, it can delay only if there was an error raised instead of delaying for every call.
import time import urllib2 from tillicum.throttle import throttle @throttle(3) def a_method(): time.sleep(1) # -> will delay 3s before returning def talk(): with throttle(3): remote = urllib2.urlopen('http://some.service:2351') return remote.read() # -> will delay 3s before returning
Timer is a generic tool for determining how long it took to execute a function or section of code. It’s used by some of the other tools in Tillicum, but is also useful on its own.
import time from tillicum.timer import timer def time_section(): with timer() as timings: time.sleep(1) return timings # -> (start_time, stop_time, duration) @timer() # Returns (return_value, timing_info) def timed_method(): time.sleep(1) return "Test 123" # -> Returns (1, "Test 123") print time_section() # [1317166112.0971849, 1317166113.0973971, 1.0002121925354004] print timed_method() # ('Test 123', [1317166113.097517, 1317166114.0976491, 1.0001320838928223])