Question: when I call generateCSVFromIncidentIdsWithArgs(list) twice with 2 different lists lets say "list1" and "list2", though the first list response appears correctly, the second list response has the results of list1 as well. I am not sure which variable to reset before making the second call so that the second list call appears without mixing the first list results.
function definition: function fetches response from a url with provided IDs in list
async def fetch(self, url, incident, session, csv):
async with session.get(url) as response:
self.format_output(incident, await response.read())
async def bound_fetch(self, sem, url, incident, session, csv):
# Getter function with semaphore.
async with sem:
await self.fetch(url, incident, session, csv)
async def run(self, r, csv):
url = self.conversations_url
tasks = []
# create instance of Semaphore
sem = asyncio.Semaphore(1000)
sslcontext = ssl.create_default_context(cafile=certifi.where())
sslcontext.load_cert_chain('certificate.pem',
'plainkey.pem')
# Create client session that will ensure we dont open new connection
# per each request.
async with ClientSession(connector=aiohttp.TCPConnector(ssl=sslcontext)) as session:
for i in r:
# pass Semaphore and session to every GET request
task = asyncio.ensure_future(self.bound_fetch(sem, url + str(i), i, session, csv))
tasks.append(task)
responses = await asyncio.gather(*tasks)
return responses
function call:
def generateCSVFromIncidentIdsWithArgs(list):
incident_list = list
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
future = asyncio.ensure_future(run(incident_list, True))
loop.run_until_complete(future)
generateCSVFromIncidentIdsWithArgs(list1)
generateCSVFromIncidentIdsWithArgs(list2)
Related
This script should take a list of initial tasks (URLs) and asynchronously make requests with aiohttp. And this part is done correctly. The problem is, since asyncio wait doesn't return actual results but only done/pending task set, I cant figure out where and how to process the results as they come, to make more requests and write data to DB. In this variant I placed the creation for a new task (make more requests...) inside the first one, which doesn't work.
PS. I am using wait because a book I am reading suggests using wait for more control over done and pending tasks and exceptions. Appreciate any help:)
async def fetch_content_2(session, url):
async with session.get(url) as result:
res = await result.text()
try:
new_link = BeautifulSoup(res, 'lxml').select_one('element on website 2')['href'])
# ***PROCESS AND WRITE SOME DATA TO DB***
except:
pass
async def fetch_content_1(session, url):
async with session.get(url) as result:
res = await result.text()
try:
link = BeautifulSoup(res, 'lxml').select_one('element on website 1')['href'])
# ***MAKE ANOTHER ASYNC REQUEST WITH NEW LINK***
asyncio.create_task(fetch_content_1(session,link))
except:
pass
async def main(tasks):
async with ClientSession() as session:
pending = [asyncio.create_task(fetch_content_1(session, url)) for url in tasks]
while pending:
done, pending = await asyncio.wait(pending, return_when=asyncio.FIRST_COMPLETED)
# print(f'Done count: {len(done)}')
# print(f'Pending count: {len(pending)}')
asyncio.run(main([url1, url2, ...]))
done and pending are sets of asyncio.Task objects. If you want to get the result of the task or its state you must get the values of the sets and call the method you need, check the (docs). Specifically you can get the result invoking the result method.
async def main(tasks):
async with ClientSession() as session:
pending = [asyncio.create_task(fetch_content_1(session, url)) for url in tasks]
while pending:
done, pending = await asyncio.wait(pending, return_when=asyncio.FIRST_COMPLETED)
res = done.pop().result()
# do some stuff with the result
Check the documentation to see the possible exceptions of call the result method and related methods. A exception may occur if the task had an internal error or the result is not ready (in this case shouldn't happen).
I would simply like to associate responses from aiohttp asynchronous HTTP requests with an identifier. I am using the following code to hit the API and extract contactproperty object which requires an external field (contacid) in order to call its API:
def get_contact_properties(self, office_name, api_key, ids, chunk_size=100, **params):
properties_pages = []
batch = 0
while True:
chunk_ids = [ids[i] for i in range(batch * chunk_size + 1, chunk_size * (1 + batch) + 1)]
urls = ["{}/{}".format(self.__get_base_url(), "contacts/{}/properties?api_key={}".format(contactid, api_key))
for contactid in chunk_ids]
responses_raw = self.get_responses(urls, self.get_office_token(office_name), chunk_size)
try:
responses_json = [json.loads(response_raw) for response_raw in responses_raw]
except Exception as e:
print(e)
valid_responses = self.__get_valid_contact_properties_responses(responses_json)
properties_pages.append(valid_responses)
if len(valid_responses) < chunk_size: # this is how we know there are no more pages with data
break
else:
batch = batch + 1
ids is a list of ids. The problem is that I do not know which response corresponds to which id so that later I can link it to contact entity using contacid. This is my fetch() function so I was wondering how to edit this function to return the contactid along with output.
async def __fetch(self, url, params, session):
async with session.get(url, params=params) as response:
output = await response.read()
return (output)
async def __bound_fetch(self, sem, url, params, session):
# Getter function with semaphore.
async with sem:
output = await self.__fetch(url, params, session)
return output
You can return the url (or whatever key identifies your request) together with the output.
Regarding using the data, I think you should read the response directly as JSON, especially since aiohttp can do this for you automatically.
async def __fetch(self, url, params, session):
async with session.get(url, params=params) as response:
try:
data = await response.json()
except ValueError as exc:
print(exc)
return None
return data
async def __bound_fetch(self, sem, url, params, session):
# Getter function with semaphore.
async with sem:
output = await self.__fetch(url, params, session)
return {"url": url, "data": data}
You did not post the get_responses function but I'm guessing something like this should work:
responses = self.get_responses(urls, self.get_office_token(office_name), chunk_size)
Responses will be a list of {"url": url, data: "data"} (data can be None for invalid responses); however with the code above one invalid request will not affect the others.
I'm using aiohttp with asyncio to make a batch of requests. My first approach was to create a session inside the fetch() function (which starts an asyncio.gather job), and then passing the session object around to the functions that perform the post requests (get_info)
def batch_starter(item_list)
return_value = loop.run_until_complete(fetch(item_list))
return return_value
async def fetch(item_list):
async with aiohttp.ClientSession() as session: # <- session started here
results = await asyncio.gather(*[asyncio.ensure_future(get_info(session, item)) for item in item_list])
async def get_info(session, item): # <- session passed to the function
async with session.post("some_url", data={"id": item}) as resp:
html = await resp.json()
some_info = html.get('info')
return some_info
but thanks to my confusion, I am now leaning towards instantiating the session right away once the script is imported, like below, at the top of the file:
import asyncio
import aiohttp
import json
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
session = aiohttp.ClientSession() # <- session started at top of file
def batch_starter(item_list)
return_value = loop.run_until_complete(fetch(item_list))
return return_value
async def fetch(item_list):
results = await asyncio.gather(*[asyncio.ensure_future(get_info(item)) for item in item_list])
async def get_info(item):
async with session.post("some_url", data={"id": item}) as resp: # <- session from outer scope is used
html = await resp.json()
some_info = html.get('info')
return some_info
the docs explain that opening a session with every request is a "very bad" idea (obviously). But this is stated right after the example which does apparently exactly that (first approach)? Which one of this is correct, and how is the session going to behave when it is used like in the second approach, at the top of the file? wouldn't the session just stay open forever if I'm using the second approach?
The batch_starter() function is not going to be called a lot, but with 9000+ items in the item_list. I assumed this was already reducing the amount of sessions to 1 (per gather job), but apparently this is the "bad idea" example, and needs to be corrected? the docs are a bit unclear about this...
I have a streaming application that almost continuously takes the data given as input and sends an HTTP request using that value and does something with the returned value.
Obviously to speed things up I've used asyncio and aiohttp libraries in Python 3.7 to get the best performance, but it becomes hard to debug given how fast the data moves.
This is what my code looks like
'''
Gets the final requests
'''
async def apiRequest(info, url, session, reqType, post_data=''):
if reqType:
async with session.post(url, data = post_data) as response:
info['response'] = await response.text()
else:
async with session.get(url+post_data) as response:
info['response'] = await response.text()
logger.debug(info)
return info
'''
Loops through the batches and sends it for request
'''
async def main(data, listOfData):
tasks = []
async with ClientSession() as session:
for reqData in listOfData:
try:
task = asyncio.ensure_future(apiRequest(**reqData))
tasks.append(task)
except Exception as e:
print(e)
exc_type, exc_obj, exc_tb = sys.exc_info()
fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
print(exc_type, fname, exc_tb.tb_lineno)
responses = await asyncio.gather(*tasks)
return responses #list of APIResponses
'''
Streams data in and prepares batches to send for requests
'''
async def Kconsumer(data, loop, batchsize=100):
consumer = AIOKafkaConsumer(**KafkaConfigs)
await consumer.start()
dataPoints = []
async for msg in consumer:
try:
sys.stdout.flush()
consumedMsg = loads(msg.value.decode('utf-8'))
if consumedMsg['tid']:
dataPoints.append(loads(msg.value.decode('utf-8')))
if len(dataPoints)==batchsize or time.time() - startTime>5:
'''
#1: The task below goes and sends HTTP GET requests in bulk using aiohttp
'''
task = asyncio.ensure_future(getRequests(data, dataPoints))
res = await asyncio.gather(*[task])
if task.done():
outputs = []
'''
#2: Does some ETL on the returned values
'''
ids = await asyncio.gather(*[doSomething(**{'tid':x['tid'],
'cid':x['cid'], 'tn':x['tn'],
'id':x['id'], 'ix':x['ix'],
'ac':x['ac'], 'output':to_dict(xmltodict.parse(x['response'],encoding='utf-8')),
'loop':loop, 'option':1}) for x in res[0]])
simplySaveDataIntoDataBase(id) # This is where I see some missing data in the database
dataPoints = []
except Exception as e:
logger.error(e)
logger.error(traceback.format_exc())
exc_type, exc_obj, exc_tb = sys.exc_info()
fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
logger.error(str(exc_type) +' '+ str(fname) +' '+ str(exc_tb.tb_lineno))
if __name__ == '__main__':
loop = asyncio.get_event_loop()
asyncio.ensure_future(Kconsumer(data, loop, batchsize=100))
loop.run_forever()
Does the ensure_future need to be awaited ?
How does aiohttp handle requests that come a little later than the others? Shouldn't it hold the whole batch back instead of forgetting about it altoghter?
Does the ensure_future need to be awaited ?
Yes, and your code is doing that already. await asyncio.gather(*tasks) awaits the provided tasks and returns their results in the same order.
Note that await asyncio.gather(*[task]) doesn't make sense, because it is equivalent to await asyncio.gather(task), which is again equivalent to await task. In other words, when you need the result of getRequests(data, dataPoints), you can write res = await getRequests(data, dataPoints) without the ceremony of first calling ensure_future() and then calling gather().
In fact, you almost never need to call ensure_future yourself:
if you need to await multiple tasks, you can pass coroutine objects directly to gather, e.g. gather(coroutine1(), coroutine2()).
if you need to spawn a background task, you can call asyncio.create_task(coroutine(...))
How does aiohttp handle requests that come a little later than the others? Shouldn't it hold the whole batch back instead of forgetting about it altoghter?
If you use gather, all requests must finish before any of them return. (That is not aiohttp policy, it's how gather works.) If you need to implement a timeout, you can use asyncio.wait_for or similar.
I wrote a script that uses a nursery and the asks module to loop through and call an API based upon the loop variables. I get responses but don't know how to return the data like you would with asyncio.
I also have a question on limiting the APIs to 5 per second.
from datetime import datetime
import asks
import time
import trio
asks.init("trio")
s = asks.Session(connections=4)
async def main():
start_time = time.time()
api_key = 'API-KEY'
org_id = 'ORG-ID'
networkIds = ['id1','id2','idn']
url = 'https://api.meraki.com/api/v0/networks/{0}/airMarshal?timespan=3600'
headers = {'X-Cisco-Meraki-API-Key': api_key, 'Content-Type': 'application/json'}
async with trio.open_nursery() as nursery:
for i in networkIds:
nursery.start_soon(fetch, url.format(i), headers)
print("Total time:", time.time() - start_time)
async def fetch(url, headers):
print("Start: ", url)
response = await s.get(url, headers=headers)
print("Finished: ", url, len(response.content), response.status_code)
if __name__ == "__main__":
trio.run(main)
When I run nursery.start_soon(fetch...) , I am printing data within fetch, but how do I return the data? I didn't see anything similar to asyncio.gather(*tasks) function.
Also, I can limit the number of sessions to 1-4, which helps get down below the 5 API per second limit, but was wondering if there was a built in way to ensure that no more than 5 APIs get called in any given second?
Returning data: pass the networkID and a dict to the fetch tasks:
async def main():
…
results = {}
async with trio.open_nursery() as nursery:
for i in networkIds:
nursery.start_soon(fetch, url.format(i), headers, results, i)
## results are available here
async def fetch(url, headers, results, i):
print("Start: ", url)
response = await s.get(url, headers=headers)
print("Finished: ", url, len(response.content), response.status_code)
results[i] = response
Alternately, create a trio.Queue to which you put the results; your main task can then read the results from the queue.
API limit: create a trio.Queue(10) and start a task along these lines:
async def limiter(queue):
while True:
await trio.sleep(0.2)
await queue.put(None)
Pass that queue to fetch, as another argument, and call await limit_queue.get() before each API call.
Based on this answers, you can define the following function:
async def gather(*tasks):
async def collect(index, task, results):
task_func, *task_args = task
results[index] = await task_func(*task_args)
results = {}
async with trio.open_nursery() as nursery:
for index, task in enumerate(tasks):
nursery.start_soon(collect, index, task, results)
return [results[i] for i in range(len(tasks))]
You can then use trio in the exact same way as asyncio by simply patching trio (adding the gather function):
import trio
trio.gather = gather
Here is a practical example:
async def child(x):
print(f"Child sleeping {x}")
await trio.sleep(x)
return 2*x
async def parent():
tasks = [(child, t) for t in range(3)]
return await trio.gather(*tasks)
print("results:", trio.run(parent))
Technically, trio.Queue has been deprecated in trio 0.9. It has been replaced by trio.open_memory_channel.
Short example:
sender, receiver = trio.open_memory_channel(len(networkIds)
async with trio.open_nursery() as nursery:
for i in networkIds:
nursery.start_soon(fetch, sender, url.format(i), headers)
async for value in receiver:
# Do your job here
pass
And in your fetch function you should call async sender.send(value) somewhere.
When I run nursery.start_soon(fetch...) , I am printing data within fetch, but how do I return the data? I didn't see anything similar to asyncio.gather(*tasks) function.
You're asking two different questions, so I'll just answer this one. Matthias already answered your other question.
When you call start_soon(), you are asking Trio to run the task in the background, and then keep going. This is why Trio is able to run fetch() several times concurrently. But because Trio keeps going, there is no way to "return" the result the way a Python function normally would. where would it even return to?
You can use a queue to let fetch() tasks send results to another task for additional processing.
To create a queue:
response_queue = trio.Queue()
When you start your fetch tasks, pass the queue as an argument and send a sentintel to the queue when you're done:
async with trio.open_nursery() as nursery:
for i in networkIds:
nursery.start_soon(fetch, url.format(i), headers)
await response_queue.put(None)
After you download a URL, put the response into the queue:
async def fetch(url, headers, response_queue):
print("Start: ", url)
response = await s.get(url, headers=headers)
# Add responses to queue
await response_queue.put(response)
print("Finished: ", url, len(response.content), response.status_code)
With the changes above, your fetch tasks will put responses into the queue. Now you need to read responses from the queue so you can process them. You might add a new function to do this:
async def process(response_queue):
async for response in response_queue:
if response is None:
break
# Do whatever processing you want here.
You should start this process function as a background task before you start any fetch tasks so that it will process responses as soon as they are received.
Read more in the Synchronizing and Communicating Between Tasks section of the Trio documentation.