Merge pull request #76 from samuelcolvin/compression-optional

make clickhouse-cityhash dependency optional

Makefile

@@ -25,7 +25,7 @@ up:
 	@poetry update
 
 deps:
-	@poetry install --no-root
+	@poetry install --extras compression --no-root
 
 style: deps
 	@isort -src $(checkfiles)

README.md

@@ -15,6 +15,13 @@
 > pip install asynch
 ```
 
+or if you want to install [`clickhouse-cityhash`](https://pypi.org/project/clickhouse-cityhash/) to enable
+transport compression
+
+```shell
+> pip install asynch[compression]
+```
+
 ## Usage
 
 Connect to ClickHouse

asynch/proto/compression/__init__.py

@@ -1,8 +1,6 @@
 import importlib
 from typing import TYPE_CHECKING, Type
 
-from clickhouse_cityhash.cityhash import CityHash128
-
 from asynch.errors import ChecksumDoesntMatchError, UnknownCompressionMethod
 from asynch.proto.protocol import CompressionMethodByte
 
@@ -74,6 +72,8 @@ def decompress_data(self, data, uncompressed_size):
         raise NotImplementedError
 
     async def get_decompressed_data(self, method_byte, compressed_hash, extra_header_size):
+        CityHash128 = import_cityhash()
+
         size_with_header = await self.reader.read_uint32()
         compressed_size = size_with_header - extra_header_size - 4
 
@@ -90,3 +90,12 @@ async def get_decompressed_data(self, method_byte, compressed_hash, extra_header
         uncompressed_size = await reader.read_uint32()
         compressed = compressed[4:compressed_size]
         return self.decompress_data(compressed, uncompressed_size)
+
+
+def import_cityhash():
+    try:
+        from clickhouse_cityhash.cityhash import CityHash128
+    except ImportError as e:
+        raise ImportError("Please install clickhouse-cityhash to enable compression") from e
+    else:
+        return CityHash128

asynch/proto/streams/compressed.py

@@ -1,7 +1,5 @@
-from clickhouse_cityhash.cityhash import CityHash128
-
 from asynch.proto import constants
-from asynch.proto.compression import BaseCompressor
+from asynch.proto.compression import BaseCompressor, import_cityhash
 from asynch.proto.context import Context
 from asynch.proto.streams.block import BlockReader, BlockWriter
 from asynch.proto.streams.buffered import (
@@ -28,6 +26,7 @@ def __init__(
         super().__init__(reader, self.writer, context)
 
     async def finalize(self):
+        CityHash128 = import_cityhash()
         await self.writer.flush()
 
         compressed = await self.get_compressed()