[GitHub] [flink] dianfu commented on a diff in pull request #19945: [FLINK-27964][python] Support Cassandra connector in Python DataStream API

[GitBox <gi...@apache.org>]

dianfu commented on code in PR #19945:
URL: https://github.com/apache/flink/pull/19945#discussion_r895628117


##########
docs/content.zh/docs/connectors/datastream/cassandra.md:
##########
@@ -195,6 +195,28 @@ CassandraSink.addSink(result)
 result.print().setParallelism(1)
 ```
 {{< /tab >}}
+{{< tab "Python" >}}
+```python
+# get the execution environment
+env = StreamExecutionEnvironment.get_execution_environment()
+
+# get input data by connecting to the socket
+text = DataStream(env._j_stream_execution_environment.socketTextStream(hostname, port, "\n"))

Review Comment:
   It would be great to introduce `socketTextStream` in PyFlink. We could do it in a separate PR.



##########
docs/content.zh/docs/connectors/datastream/cassandra.md:
##########
@@ -195,6 +195,28 @@ CassandraSink.addSink(result)
 result.print().setParallelism(1)
 ```
 {{< /tab >}}
+{{< tab "Python" >}}
+```python
+# get the execution environment
+env = StreamExecutionEnvironment.get_execution_environment()
+
+# get input data by connecting to the socket
+text = DataStream(env._j_stream_execution_environment.socketTextStream(hostname, port, "\n"))
+
+# parse the data, group it, window it, and aggregate the counts
+result = text \
+    .flat_map(lambda x: x.lower.split("\\s")) \

Review Comment:
   .filter(lambda x: len(x) > 0)



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options
+
+
+class CassandraFailureHandler(object):
+    """
+    Handle a failed Throwable.
+    """
+    def __init__(self, j_cassandra_failure_handler):
+        self._j_cassandra_failure_handler = j_cassandra_failure_handler
+
+
+class ClusterBuilder(object):
+    """
+    This class is used to configure a Cluster after deployment. The cluster represents the
+    connection that will be established to Cassandra.
+    """
+    def __init__(self, j_cluster_builder):
+        self._j_cluster_builder = j_cluster_builder
+
+
+class CheckpointCommitter(object):
+    """
+    CheckpointCommitter that saves information about completed checkpoints within a separate table
+    in a cassandra database.
+    """
+    def __init__(self, j_checkpoint_committer):
+        self._j_checkpoint_committer = j_checkpoint_committer
+
+    @staticmethod
+    def cassandra_committer(builder: ClusterBuilder, key_space: str = None) \

Review Comment:
   If we rename CheckpointCommitter to CassandraCommitter, then we could rename this method to default_checkpoint_committer



##########
docs/content.zh/docs/connectors/datastream/cassandra.md:
##########
@@ -283,6 +305,51 @@ public class WordCount {
 }
 ```
 {{< /tab >}}
+{{< tab "Python" >}}
+```python
+# get the execution environment
+env = StreamExecutionEnvironment.get_execution_environment()
+
+# get input data by connecting to the socket
+text = DataStream(env._j_stream_execution_environment.socketTextStream(hostname, port, "\n"))
+
+# parse the data, group it, window it, and aggregate the counts
+result = text \
+    .flat_map(lambda x: x.lower.split("\\s")) \
+    .map(lambda x: (x, 1), output_type=Types.TUPLE([WordCount, Types.INT()])) \
+    .key_by(lambda x: x.get_word()) \
+    .window(TumblingProcessingTimeWindows.of(Time.seconds(5))) \
+    .reduce(lambda a, b: WordCount(a.get_word(), a.get_count() + b.get_count()))
+
+CassandraSink.add_sink(result) \
+    .set_host("127.0.0.1") \
+    .set_mapper_options(MapperOptions(JMyMapperOptions)) \

Review Comment:
   This is not executable. Could you make it more concrete?



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options
+
+
+class CassandraFailureHandler(object):
+    """
+    Handle a failed Throwable.
+    """
+    def __init__(self, j_cassandra_failure_handler):
+        self._j_cassandra_failure_handler = j_cassandra_failure_handler
+
+
+class ClusterBuilder(object):
+    """
+    This class is used to configure a Cluster after deployment. The cluster represents the
+    connection that will be established to Cassandra.
+    """
+    def __init__(self, j_cluster_builder):
+        self._j_cluster_builder = j_cluster_builder
+
+
+class CheckpointCommitter(object):
+    """
+    CheckpointCommitter that saves information about completed checkpoints within a separate table
+    in a cassandra database.
+    """
+    def __init__(self, j_checkpoint_committer):
+        self._j_checkpoint_committer = j_checkpoint_committer
+
+    @staticmethod
+    def cassandra_committer(builder: ClusterBuilder, key_space: str = None) \
+            -> 'CheckpointCommitter':
+        """
+        CheckpointCommitter that saves information about completed checkpoints within a separate
+        table in a cassandra database.
+        """
+        if key_space is None:
+            j_checkpoint_committer = get_gateway().jvm.org.apache.flink.streaming. \
+                connectors.cassandra.CassandraCommitter(builder._j_cluster_builder)
+        else:
+            j_checkpoint_committer = get_gateway().jvm.org.apache.flink.streaming. \
+                connectors.cassandra.CassandraCommitter(builder._j_cluster_builder, key_space)
+        return CheckpointCommitter(j_checkpoint_committer)
+
+
+class CassandraSink(Sink):

Review Comment:
   ```suggestion
   class CassandraSink(object):
   ```
   
   CassandraSink could not extends from Sink directly as it doesn't support `datastream.sink_to(cassandra_sink)`



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options
+
+
+class CassandraFailureHandler(object):
+    """
+    Handle a failed Throwable.
+    """
+    def __init__(self, j_cassandra_failure_handler):
+        self._j_cassandra_failure_handler = j_cassandra_failure_handler
+
+
+class ClusterBuilder(object):
+    """
+    This class is used to configure a Cluster after deployment. The cluster represents the
+    connection that will be established to Cassandra.
+    """
+    def __init__(self, j_cluster_builder):
+        self._j_cluster_builder = j_cluster_builder
+
+
+class CheckpointCommitter(object):

Review Comment:
   I guess we could rename it to CassandraCommitter



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options

Review Comment:
   Could we introduce a builder and add the following methods insider the builder to make this easy to use for Python users:
   ```
   def ttl(ttl: int):
   
   def timerstamp(timestamp: int):
   
   def consistency_level(xxx)
   
   def tracing(enabled: bool):
   
   def save_null_fields(enabled: bool):
   ```



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options
+
+
+class CassandraFailureHandler(object):
+    """
+    Handle a failed Throwable.
+    """
+    def __init__(self, j_cassandra_failure_handler):
+        self._j_cassandra_failure_handler = j_cassandra_failure_handler

Review Comment:
   Add a default method which returns NoOpCassandraFailureHandler:
   ```
   def default_failure_handler()
   ```



##########
flink-python/pyflink/datastream/connectors/cassandra.py:
##########
@@ -0,0 +1,253 @@
+################################################################################
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+# limitations under the License.
+################################################################################
+from pyflink.common import Duration
+from pyflink.datastream import DataStream
+from pyflink.datastream.connectors import Sink
+from pyflink.java_gateway import get_gateway
+
+
+class MapperOptions(object):
+    """
+    This class is used to configure a Mapper after deployment.
+    """
+    def __init__(self, j_mapper_options):
+        self._j_mapper_options = j_mapper_options
+
+
+class CassandraFailureHandler(object):
+    """
+    Handle a failed Throwable.
+    """
+    def __init__(self, j_cassandra_failure_handler):
+        self._j_cassandra_failure_handler = j_cassandra_failure_handler
+
+
+class ClusterBuilder(object):
+    """
+    This class is used to configure a Cluster after deployment. The cluster represents the
+    connection that will be established to Cassandra.
+    """
+    def __init__(self, j_cluster_builder):
+        self._j_cluster_builder = j_cluster_builder
+

Review Comment:
   Add a builder with the following methods to make it more usable for Python users:
   ```
   with_cluster_name、with_port、with_port、with_max_schema_agreement_wait_seconds、with_protocol_version, add_contact_point, add_contact_points, with_load_balancing_policy, with_reconnection_policy, with_retry_policy,  etc.
   ```
   
   See the Java Cluster.Builder defined in cassandra for more details.



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