Support for loading, unloading and listing Redis Modules (#1360)

* Support for loading, unloading and listing Redis Modules

* minor fixes for flake

* unit test for module list - only the empty use case

* ModuleError should inherit from ResponseError rather than RedisError

Co-authored-by: Vamsi Atluri <vamc19@gmail.com>

4 files changed, 55 insertions, 0 deletions

diff --git a/redis/client.py b/redis/client.py
index 9de90fb..9653f7d 100755
--- a/redis/client.py
+++ b/redis/client.py
@@ -22,6 +22,7 @@ from redis.exceptions import (
     ResponseError,
     TimeoutError,
     WatchError,
+    ModuleError,
 )
 
 SYM_EMPTY = b''
@@ -516,6 +517,12 @@ def parse_acl_getuser(response, **options):
     return data
 
 
+def parse_module_result(response):
+    if isinstance(response, ModuleError):
+        raise response
+    return True
+
+
 class Redis(object):
     """
     Implementation of the Redis protocol.
@@ -656,6 +663,10 @@ class Redis(object):
             'XPENDING': parse_xpending,
             'ZADD': parse_zadd,
             'ZSCAN': parse_zscan,
+            'MODULE LOAD': parse_module_result,
+            'MODULE UNLOAD': parse_module_result,
+            'MODULE LIST': lambda response: [pairs_to_dict(module)
+                                             for module in response],
         }
     )
 
@@ -3306,6 +3317,28 @@ class Redis(object):
 
         return self.execute_command(command, *pieces, **kwargs)
 
+    # MODULE COMMANDS
+    def module_load(self, path):
+        """
+        Loads the module from ``path``.
+        Raises ``ModuleError`` if a module is not found at ``path``.
+        """
+        return self.execute_command('MODULE LOAD', path)
+
+    def module_unload(self, name):
+        """
+        Unloads the module ``name``.
+        Raises ``ModuleError`` if ``name`` is not in loaded modules.
+        """
+        return self.execute_command('MODULE UNLOAD', name)
+
+    def module_list(self):
+        """
+        Returns a list of dictionaries containing the name and version of
+        all loaded modules.
+        """
+        return self.execute_command('MODULE LIST')
+
 
 StrictRedis = Redis
 
diff --git a/redis/connection.py b/redis/connection.py
index e3c9b66..b08aee9 100755
--- a/redis/connection.py
+++ b/redis/connection.py
@@ -29,6 +29,7 @@ from redis.exceptions import (
     RedisError,
     ResponseError,
     TimeoutError,
+    ModuleError,
 )
 from redis.utils import HIREDIS_AVAILABLE
 
@@ -90,6 +91,14 @@ SYM_EMPTY = b''
 SERVER_CLOSED_CONNECTION_ERROR = "Connection closed by server."
 
 SENTINEL = object()
+MODULE_LOAD_ERROR = 'Error loading the extension. ' \
+                    'Please check the server logs.'
+NO_SUCH_MODULE_ERROR = 'Error unloading module: no such module with that name'
+MODULE_UNLOAD_NOT_POSSIBLE_ERROR = 'Error unloading module: operation not ' \
+                                   'possible.'
+MODULE_EXPORTS_DATA_TYPES_ERROR = "Error unloading module: the module " \
+                                  "exports one or more module-side data " \
+                                  "types, can't unload"
 
 
 class Encoder(object):
@@ -146,6 +155,10 @@ class BaseParser(object):
             # in uppercase
             'wrong number of arguments for \'AUTH\' command':
                 AuthenticationWrongNumberOfArgsError,
+            MODULE_LOAD_ERROR: ModuleError,
+            MODULE_EXPORTS_DATA_TYPES_ERROR: ModuleError,
+            NO_SUCH_MODULE_ERROR: ModuleError,
+            MODULE_UNLOAD_NOT_POSSIBLE_ERROR: ModuleError,
         },
         'EXECABORT': ExecAbortError,
         'LOADING': BusyLoadingError,
diff --git a/redis/exceptions.py b/redis/exceptions.py
index 760af66..ca2ad87 100644
--- a/redis/exceptions.py
+++ b/redis/exceptions.py
@@ -57,6 +57,10 @@ class NoPermissionError(ResponseError):
     pass
 
 
+class ModuleError(ResponseError):
+    pass
+
+
 class LockError(RedisError, ValueError):
     "Errors acquiring or releasing a lock"
     # NOTE: For backwards compatability, this class derives from ValueError.
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 65e877c..adaa9fc 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -2629,6 +2629,11 @@ class TestRedisCommands(object):
         r.set('foo', 'bar')
         assert isinstance(r.memory_usage('foo'), int)
 
+    @skip_if_server_version_lt('4.0.0')
+    def test_module_list(self, r):
+        assert isinstance(r.module_list(), list)
+        assert not r.module_list()
+
 
 class TestBinarySave(object):