Introduce OutOfMemoryError exception for Redis write command rejectio…

…ns due to OOM errors (#2778)

* expose OutOfMemoryError as explicit exception type

- handle "OOM" error code string by raising explicit
  exception type instance
- enables callers to avoid string matching after
  catching ResponseError

* add OutOfMemoryError exception class docstring

* Provide more info in the exception docstring

* Fix formatting

* Again

* linters

---------

Co-authored-by: Chayim <chayim@users.noreply.github.com>
Co-authored-by: Igor Malinovskiy <u.glide@gmail.com>
Co-authored-by: dvora-h <67596500+dvora-h@users.noreply.github.com>

redis/__init__.py

@@ -19,6 +19,7 @@
     ConnectionError,
     DataError,
     InvalidResponse,
+    OutOfMemoryError,
     PubSubError,
     ReadOnlyError,
     RedisError,
@@ -72,6 +73,7 @@ def int_or_str(value):
     "from_url",
     "default_backoff",
     "InvalidResponse",
+    "OutOfMemoryError",
     "PubSubError",
     "ReadOnlyError",
     "Redis",

redis/asyncio/__init__.py

@@ -24,6 +24,7 @@
     ConnectionError,
     DataError,
     InvalidResponse,
+    OutOfMemoryError,
     PubSubError,
     ReadOnlyError,
     RedisError,
@@ -47,6 +48,7 @@
     "default_backoff",
     "InvalidResponse",
     "PubSubError",
+    "OutOfMemoryError",
     "ReadOnlyError",
     "Redis",
     "RedisCluster",

redis/asyncio/connection.py

@@ -49,6 +49,7 @@
     ModuleError,
     NoPermissionError,
     NoScriptError,
+    OutOfMemoryError,
     ReadOnlyError,
     RedisError,
     ResponseError,
@@ -174,6 +175,7 @@ class BaseParser:
         "READONLY": ReadOnlyError,
         "NOAUTH": AuthenticationError,
         "NOPERM": NoPermissionError,
+        "OOM": OutOfMemoryError,
     }
 
     def __init__(self, socket_read_size: int):

redis/connection.py

@@ -28,6 +28,7 @@
     ModuleError,
     NoPermissionError,
     NoScriptError,
+    OutOfMemoryError,
     ReadOnlyError,
     RedisError,
     ResponseError,
@@ -149,6 +150,7 @@ class BaseParser:
             MODULE_UNLOAD_NOT_POSSIBLE_ERROR: ModuleError,
             **NO_AUTH_SET_ERROR,
         },
+        "OOM": OutOfMemoryError,
         "WRONGPASS": AuthenticationError,
         "EXECABORT": ExecAbortError,
         "LOADING": BusyLoadingError,

redis/exceptions.py

@@ -49,6 +49,18 @@ class NoScriptError(ResponseError):
     pass
 
 
+class OutOfMemoryError(ResponseError):
+    """
+    Indicates the database is full. Can only occur when either:
+      * Redis maxmemory-policy=noeviction
+      * Redis maxmemory-policy=volatile* and there are no evictable keys
+
+    For more information see `Memory optimization in Redis <https://redis.io/docs/management/optimization/memory-optimization/#memory-allocation>`_. # noqa
+    """
+
+    pass
+
+
 class ExecAbortError(ResponseError):
     pass
 

tests/test_asyncio/test_connection_pool.py

@@ -606,10 +606,18 @@ async def test_busy_loading_from_pipeline(self, r):
     @skip_if_server_version_lt("2.8.8")
     @skip_if_redis_enterprise()
     async def test_read_only_error(self, r):
-        """READONLY errors get turned in ReadOnlyError exceptions"""
+        """READONLY errors get turned into ReadOnlyError exceptions"""
         with pytest.raises(redis.ReadOnlyError):
             await r.execute_command("DEBUG", "ERROR", "READONLY blah blah")
 
+    @skip_if_redis_enterprise()
+    async def test_oom_error(self, r):
+        """OOM errors get turned into OutOfMemoryError exceptions"""
+        with pytest.raises(redis.OutOfMemoryError):
+            # note: don't use the DEBUG OOM command since it's not the same
+            # as the db being full
+            await r.execute_command("DEBUG", "ERROR", "OOM blah blah")
+
     def test_connect_from_url_tcp(self):
         connection = redis.Redis.from_url("redis://localhost")
         pool = connection.connection_pool

tests/test_connection_pool.py

@@ -528,10 +528,17 @@ def test_busy_loading_from_pipeline(self, r):
     @skip_if_server_version_lt("2.8.8")
     @skip_if_redis_enterprise()
     def test_read_only_error(self, r):
-        "READONLY errors get turned in ReadOnlyError exceptions"
+        "READONLY errors get turned into ReadOnlyError exceptions"
         with pytest.raises(redis.ReadOnlyError):
             r.execute_command("DEBUG", "ERROR", "READONLY blah blah")
 
+    def test_oom_error(self, r):
+        "OOM errors get turned into OutOfMemoryError exceptions"
+        with pytest.raises(redis.OutOfMemoryError):
+            # note: don't use the DEBUG OOM command since it's not the same
+            # as the db being full
+            r.execute_command("DEBUG", "ERROR", "OOM blah blah")
+
     def test_connect_from_url_tcp(self):
         connection = redis.Redis.from_url("redis://localhost")
         pool = connection.connection_pool