Possibility to ignore cache errors

pyvec · Feb 15, 2018 · 27d1b75 · 27d1b75
1 parent 1720905
commit 27d1b75
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Showing 2 changed files with 57 additions and 8 deletions.
diff --git a/arca/_arca.py b/arca/_arca.py
@@ -20,28 +20,33 @@
 
 class Arca:
 
-    single_pull: bool = LazySettingProperty(key="single_pull", default=False)
+    single_pull: bool = LazySettingProperty(key="single_pull", default=False, convert=bool)
     base_dir: str = LazySettingProperty(key="base_dir", default=".arca")
+    ignore_cache_errors: bool = LazySettingProperty(key="ignore_cache_errors", default=False, convert=bool)
 
     def __init__(self, backend: BackendDefinitionType=NOT_SET,
                  settings=None,
                  single_pull=None,
-                 base_dir=None) -> None:
+                 base_dir=None,
+                 ignore_cache_errors=None) -> None:
         self.settings: Settings = self._get_settings(settings)
 
-        self.region: CacheRegion = self._make_region()
-
-        self.backend: BaseBackend = self._get_backend_instance(backend)
-        self.backend.inject_arca(self)
-
-        self._current_hash = defaultdict(lambda: {})
+        if ignore_cache_errors is not None:
+            self.ignore_cache_errors = bool(ignore_cache_errors)
 
         if single_pull is not None:
             self.single_pull = bool(single_pull)
 
         if base_dir is not None:
             self.base_dir = base_dir
 
+        self.region: CacheRegion = self._make_region()
+
+        self.backend: BaseBackend = self._get_backend_instance(backend)
+        self.backend.inject_arca(self)
+
+        self._current_hash = defaultdict(lambda: {})
+
     def _get_backend_instance(self, backend: BackendDefinitionType) -> BaseBackend:
         if backend is NOT_SET:
             backend = self.get_setting("backend", "arca.backend.VenvBackend")
@@ -72,10 +77,17 @@ def _get_settings(self, settings: Optional[Dict[str, Any]]) -> Settings:
     def _make_region(self) -> CacheRegion:
         arguments = self.get_setting("cache_backend_arguments", None)
 
+        def null_cache():
+            return make_region().configure(
+                "dogpile.cache.null"
+            )
+
         if isinstance(arguments, str) and arguments:
             try:
                 arguments = json.loads(arguments)
             except ValueError:
+                if self.ignore_cache_errors:
+                    return null_cache()
                 raise ArcaMisconfigured("Cache backend arguments couldn't be converted to a dictionary.")
 
         try:
@@ -86,8 +98,12 @@ def _make_region(self) -> CacheRegion:
             )
             region.set("last_arca_run", datetime.now().isoformat())
         except ModuleNotFoundError:
+            if self.ignore_cache_errors:
+                return null_cache()
             raise ModuleNotFoundError("Cache backend cannot load a required library.")
         except Exception:
+            if self.ignore_cache_errors:
+                return null_cache()
             raise ArcaMisconfigured("The provided cache is not working - most likely misconfigured.")
 
         return region

diff --git a/tests/test_cache.py b/tests/test_cache.py
@@ -115,3 +115,36 @@ def test_invalid_arguments():
                  "ARCA_CACHE_BACKEND": "dogpile.cache.dbm",
                  "ARCA_CACHE_BACKEND_ARGUMENTS": json.dumps({"filename": str(Path(BASE_DIR) / "cachefile.dbm")})[:-1]
              })
+
+    # in case ignore is set, no error thrown, region configred
+    arca = Arca(base_dir=BASE_DIR,
+                single_pull=True,
+                ignore_cache_errors=True,
+                settings={
+                    "ARCA_CACHE_BACKEND": "dogpile.cache.dbm",
+                    "ARCA_CACHE_BACKEND_ARGUMENTS": json.dumps({"filename": str(Path(BASE_DIR) / "cachefile.dbm")})[:-1]
+                })
+
+    assert arca.region.is_configured
+
+
+def test_cache_backend_module_not_found():
+    # redis must not be present in the env
+    with pytest.raises(ImportError):
+        import redis  # noqa
+
+    with pytest.raises(ModuleNotFoundError):
+        Arca(base_dir=BASE_DIR,
+             single_pull=True,
+             settings={
+                 "ARCA_CACHE_BACKEND": "dogpile.cache.redis"
+             })
+
+    arca = Arca(base_dir=BASE_DIR,
+                single_pull=True,
+                ignore_cache_errors=True,
+                settings={
+                    "ARCA_CACHE_BACKEND": "dogpile.cache.redis"
+                })
+
+    assert arca.region.is_configured