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Improve cache (#7227) 

* Improve cache

* Improve code, add docs

* Simplify flow

* Update docstring
This commit is contained in:
Beto Dealmeida 2019-04-09 11:05:44 -07:00 committed by Christine Chambers
parent 51544212b6
commit 51472e9035
1 changed files with 40 additions and 23 deletions
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63
superset/utils/decorators.py
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@ -47,12 +47,13 @@ def etag_cache(max_age, check_perms=bool):
"""
A decorator for caching views and handling etag conditional requests.
The decorator caches the response, returning headers for etag and last
modified. If the client makes a request that matches, the server will
return a "304 Not Mofified" status.
The decorator adds headers to GET requests that help with caching: Last-
Modified, Expires and ETag. It also handles conditional requests, when the
client send an If-Matches header.
If no cache is set, the decorator will still set the ETag header, and
handle conditional requests.
If a cache is set, the decorator will cache GET responses, bypassing the
dataframe serialization. POST requests will still benefit from the
dataframe cache for requests that produce the same SQL.
"""
def decorator(f):
@ -61,30 +62,46 @@ def etag_cache(max_age, check_perms=bool):
# check if the user can access the resource
check_perms(*args, **kwargs)
try:
# build the cache key from the function arguments and any other
# additional GET arguments (like `form_data`, eg).
key_args = list(args)
key_kwargs = kwargs.copy()
key_kwargs.update(request.args)
cache_key = wrapper.make_cache_key(f, *key_args, **key_kwargs)
response = cache.get(cache_key)
except Exception: # pylint: disable=broad-except
if app.debug:
raise
logging.exception('Exception possibly due to cache backend.')
response = None
# for POST requests we can't set cache headers, use the response
# cache nor use conditional requests; this will still use the
# dataframe cache in `superset/viz.py`, though.
if request.method == 'POST':
return f(*args, **kwargs)
if response is None or request.method == 'POST':
response = None
if cache:
try:
# build the cache key from the function arguments and any
# other additional GET arguments (like `form_data`, eg).
key_args = list(args)
key_kwargs = kwargs.copy()
key_kwargs.update(request.args)
cache_key = wrapper.make_cache_key(f, *key_args, **key_kwargs)
response = cache.get(cache_key)
except Exception: # pylint: disable=broad-except
if app.debug:
raise
logging.exception('Exception possibly due to cache backend.')
# if no response was cached, compute it using the wrapped function
if response is None:
response = f(*args, **kwargs)
# add headers for caching: Last Modified, Expires and ETag
response.cache_control.public = True
response.last_modified = datetime.utcnow()
expiration = max_age if max_age != 0 else FAR_FUTURE
response.expires = response.last_modified + timedelta(seconds=expiration)
response.expires = \
response.last_modified + timedelta(seconds=expiration)
response.add_etag()
try:
cache.set(cache_key, response, timeout=max_age)
except Exception: # pylint: disable=broad-except
# if we have a cache, store the response from the request
if cache:
try:
cache.set(cache_key, response, timeout=max_age)
except Exception: # pylint: disable=broad-except
if app.debug:
raise
logging.exception('Exception possibly due to cache backend.')
return response.make_conditional(request)