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c21130eed9
* module docstrings * db schema graph * dev docs first pass * dev docs pass 2 * add generated notification to top of generated docs files * linting * regen docs Co-authored-by: Stefan Pratter <stefan@20c.com> Co-authored-by: Sunshine Buchholz <sunshine@20c.com>
118 lines
3.4 KiB
Python
118 lines
3.4 KiB
Python
"""
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Handle loading of api-cache data.
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"""
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import json
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import os
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from django.conf import settings
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class CacheRedirect(Exception):
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"""
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Raise this error to redirect to cache response during viewset.get_queryset
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or viewset.list()
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Argument should be an APICacheLoader instance.
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"""
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def __init__(self, loader):
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super().__init__(self, "Result to be loaded from cache")
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self.loader = loader
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###############################################################################
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# API CACHE LOADER
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class APICacheLoader:
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"""
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Checks if an API GET request qualifies for a cache load
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and if it does allows you to provide the cached result.
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"""
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def __init__(self, viewset, qset, filters):
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request = viewset.request
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self.request = request
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self.qset = qset
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self.filters = filters
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self.model = viewset.model
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self.viewset = viewset
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self.depth = min(int(request.query_params.get("depth", 0)), 3)
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self.limit = int(request.query_params.get("limit", 0))
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self.skip = int(request.query_params.get("skip", 0))
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self.since = int(request.query_params.get("since", 0))
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self.fields = request.query_params.get("fields")
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if self.fields:
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self.fields = self.fields.split(",")
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self.path = os.path.join(
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settings.API_CACHE_ROOT,
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f"{viewset.model.handleref.tag}-{self.depth}.json",
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)
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def qualifies(self):
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"""
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Check if request qualifies for a cache load.
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"""
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# api cache use is disabled, no
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if not getattr(settings, "API_CACHE_ENABLED", False):
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return False
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# no depth and a limit lower than 251 seems like a tipping point
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# were non-cache retrieval is faster still
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if (
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not self.depth
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and self.limit
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and self.limit <= 250
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and getattr(settings, "API_CACHE_ALL_LIMITS", False) is False
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):
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return False
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# filters have been specified, no
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if self.filters or self.since:
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return False
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# cache file non-existant, no
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if not os.path.exists(self.path):
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return False
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# request method is anything but GET, no
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if self.request.method != "GET":
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return False
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# primary key set in request, no
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if self.viewset.kwargs:
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return False
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return True
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def load(self):
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"""
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Load the cached response according to tag and depth.
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"""
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# read cache file
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with open(self.path) as f:
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data = json.load(f)
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data = data.get("data")
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# apply pagination
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if self.skip and self.limit:
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data = data[self.skip : self.skip + self.limit]
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elif self.skip:
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data = data[self.skip :]
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elif self.limit:
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data = data[: self.limit]
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if self.fields:
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for row in data:
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self.filter_fields(row)
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return {"results": data, "__meta": {"generated": os.path.getmtime(self.path)}}
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def filter_fields(self, row):
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"""
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Remove any unwanted fields from the resultset
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according to the `fields` filter specified in the request.
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"""
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for field in list(row.keys()):
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if field not in self.fields and field != "_grainy":
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del row[field]
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