Cache GIDD exports using S3

apps/gidd/cache.py

@@ -0,0 +1,133 @@
+import typing
+import hashlib
+import os
+import json
+import django_filters
+from django.db import models
+from django.core.serializers.json import DjangoJSONEncoder
+from django.core.files.base import ContentFile
+from rest_framework.request import Request
+from storages.backends.s3boto3 import S3Boto3Storage
+
+from helix.storages import get_external_storage
+
+from .models import StatusLog, ReleaseMetadata
+
+external_storage = get_external_storage()
+
+
+class ExternalStorageEnableAuthString:
+    initial_value = getattr(external_storage, 'querystring_auth', None)
+
+    def __enter__(self):
+        if isinstance(external_storage, S3Boto3Storage):
+            external_storage.querystring_auth = True
+
+    def __exit__(self, exc_type, exc_value, exc_tb):
+        if isinstance(external_storage, S3Boto3Storage):
+            external_storage.querystring_auth = self.initial_value
+
+
+class GiddExportCache:
+
+    FILE_DESTINATION_PREFIX = 'gidd-cache-export'
+
+    class Key(models.TextChoices):
+        # {StatusLog.id}/{export-name}/{export-hash}
+        DISAGGREGATION_EXPORT = 'disaggregation-export'
+        DISAGGREGATION_EXPORT_GEOJSON = 'disaggregation-export-geojson'
+        DISASTER_EXPORT = 'disaster-export'
+        DISPLACEMENT_EXPORT = 'displacement-export'
+
+    @staticmethod
+    def last_release_date() -> str:
+        return StatusLog.last_release_date(strf_format='%Y-%m-%d-%H-%M-%S') or 'NA'
+
+    @classmethod
+    def generate_cache_key(cls, key: Key, data: dict, filename: str) -> typing.Tuple[bytes, str]:
+        last_release_date = cls.last_release_date()
+
+        hashable = json.dumps(
+            data,
+            sort_keys=True,
+            cls=DjangoJSONEncoder,
+        ).encode('utf-8')
+
+        hash_md5 = hashlib.md5()
+        hash_md5.update(hashable)
+        return hashable, os.path.join(
+            cls.FILE_DESTINATION_PREFIX,
+            '{}',
+            key,
+            '{}',
+            filename,
+        ).format(last_release_date, hash_md5.hexdigest())
+
+    @classmethod
+    def _get_or_create(
+        cls,
+        key: Key,
+        data: dict,
+        filename: str,
+        export_generator: typing.Callable,
+    ) -> str:
+        key_data, cache_key = cls.generate_cache_key(key, data, filename)
+        if external_storage.exists(cache_key):
+            return cache_key
+        # Save file as well
+        external_storage.save(cache_key, ContentFile(export_generator()))
+        # Save metadata as well
+        external_storage.save(f"{cache_key}.json", ContentFile(key_data))
+        return cache_key
+
+    @classmethod
+    def get_or_create(
+        cls,
+        filename: str,
+        request: Request,
+        filter_sets: typing.List[django_filters.FilterSet],
+        key: Key,
+        export_generator: typing.Callable,
+        s3_parameters: dict,
+    ) -> str:
+        release_meta_data = ReleaseMetadata.objects.last()
+        if not release_meta_data:
+            # TODO:
+            raise Exception('Release metadata is not configured.')
+
+        release_year = release_meta_data.release_year
+        if (
+            request.query_params.get('release_environment').lower() ==
+            ReleaseMetadata.ReleaseEnvironment.PRE_RELEASE.name.lower()
+        ):
+            release_year = release_meta_data.pre_release_year
+
+        # Only look at fields used by filter_set
+        clean_data = {
+            k: v
+            for k, v in request.query_params.items()
+            if k in [
+                field
+                for filter_set in filter_sets
+                for field in filter_set.get_filters()
+            ]
+        }
+        # Remove client_id is exists
+        clean_data.pop('cliend_id', None)
+        # release_environment is replaced by release_year
+        clean_data.pop('release_environment', None)
+        data = {
+            **clean_data,
+            'release_year': release_year,
+        }
+
+        cache_key = cls._get_or_create(key, data, filename, export_generator)
+        if isinstance(external_storage, S3Boto3Storage):
+            with ExternalStorageEnableAuthString():
+                return external_storage.url(
+                    cache_key,
+                    parameters=s3_parameters,
+                )
+        return request.build_absolute_uri(
+            external_storage.url(cache_key)
+        )

apps/gidd/models.py

@@ -1,3 +1,4 @@
+import typing
 from django.db import models
 from django.utils.translation import gettext_lazy as _
 from django_enumfield import enum
@@ -158,9 +159,9 @@ def __str__(self):
         return str(self.triggered_at)
 
     @classmethod
-    def last_release_date(cls):
-        last_log = StatusLog.objects.last()
-        return last_log.completed_at.strftime("%B %d, %Y") if last_log else None
+    def last_release_date(cls, strf_format: str = "%B %d, %Y") -> typing.Optional[str]:
+        if last_log := StatusLog.objects.filter(completed_at__isnull=False).last():
+            return last_log.completed_at.strftime(strf_format)
 
 
 class ConflictLegacy(models.Model):