flags2 await refactoring start

17-futures/countries/flags2_await.py

@@ -0,0 +1,118 @@
+"""Download flags of countries (with error handling).
+
+asyncio version
+
+Sample run::
+
+    $ python3 flags2_asyncio.py -s ERROR -e -m 200
+    ERROR site: http://localhost:8003/flags
+    Searching for 676 flags: from AA to ZZ
+    200 concurrent connections will be used.
+    --------------------
+    146 flags downloaded.
+    363 not found.
+    167 errors.
+    Elapsed time: 2.59s
+
+"""
+# BEGIN FLAGS2_ASYNCIO_TOP
+import asyncio
+import collections
+
+import aiohttp
+from aiohttp import web
+import tqdm
+
+from flags2_common import main, HTTPStatus, Result, save_flag
+
+# default set low to avoid errors from remote site, such as
+# 503 - Service Temporarily Unavailable
+DEFAULT_CONCUR_REQ = 5
+MAX_CONCUR_REQ = 1000
+
+
+class FetchError(Exception):  # <1>
+    def __init__(self, country_code):
+        self.country_code = country_code
+
+
+@asyncio.coroutine
+def get_flag(base_url, cc): # <2>
+    url = '{}/{cc}/{cc}.gif'.format(base_url, cc=cc.lower())
+    resp = yield from aiohttp.request('GET', url)
+    if resp.status == 200:
+        image = yield from resp.read()
+        return image
+    elif resp.status == 404:
+        raise web.HTTPNotFound()
+    else:
+        raise aiohttp.HttpProcessingError(
+            code=resp.status, message=resp.reason,
+            headers=resp.headers)
+
+
+@asyncio.coroutine
+def download_one(cc, base_url, semaphore, verbose):  # <3>
+    try:
+        with (yield from semaphore):  # <4>
+            image = yield from get_flag(base_url, cc)  # <5>
+    except web.HTTPNotFound:  # <6>
+        status = HTTPStatus.not_found
+        msg = 'not found'
+    except Exception as exc:
+        raise FetchError(cc) from exc  # <7>
+    else:
+        save_flag(image, cc.lower() + '.gif')  # <8>
+        status = HTTPStatus.ok
+        msg = 'OK'
+
+    if verbose and msg:
+        print(cc, msg)
+
+    return Result(status, cc)
+# END FLAGS2_ASYNCIO_TOP
+
+# BEGIN FLAGS2_ASYNCIO_DOWNLOAD_MANY
+@asyncio.coroutine
+def downloader_coro(cc_list, base_url, verbose, concur_req):  # <1>
+    counter = collections.Counter()
+    semaphore = asyncio.Semaphore(concur_req)  # <2>
+    to_do = [download_one(cc, base_url, semaphore, verbose)
+             for cc in sorted(cc_list)]  # <3>
+
+    to_do_iter = asyncio.as_completed(to_do)  # <4>
+    if not verbose:
+        to_do_iter = tqdm.tqdm(to_do_iter, total=len(cc_list))  # <5>
+    for future in to_do_iter:  # <6>
+        try:
+            res = yield from future  # <7>
+        except FetchError as exc:  # <8>
+            country_code = exc.country_code  # <9>
+            try:
+                error_msg = exc.__cause__.args[0]  # <10>
+            except IndexError:
+                error_msg = exc.__cause__.__class__.__name__  # <11>
+            if verbose and error_msg:
+                msg = '*** Error for {}: {}'
+                print(msg.format(country_code, error_msg))
+            status = HTTPStatus.error
+        else:
+            status = res.status
+
+        counter[status] += 1  # <12>
+
+    return counter  # <13>
+
+
+def download_many(cc_list, base_url, verbose, concur_req):
+    loop = asyncio.get_event_loop()
+    coro = downloader_coro(cc_list, base_url, verbose, concur_req)
+    counts = loop.run_until_complete(coro)  # <14>
+    loop.close()  # <15>
+
+    return counts
+
+
+if __name__ == '__main__':
+    main(download_many, DEFAULT_CONCUR_REQ, MAX_CONCUR_REQ)
+# END FLAGS2_ASYNCIO_DOWNLOAD_MANY