[Issue-624] Python API support for the new unified sink

[thekingofcity]

Signed-off-by: thekingofcity [email protected]

Change log description

Upgrade the Python wrapper to match the new unified sink API implemented in #460.

Purpose of the change

Fix #624

What the code does

Add a Python PravegaSink wrapper that inherits Sink.

How to verify it

from pyflink.common.serialization import SimpleStringSchema
from pyflink.common.typeinfo import Types
from pyflink.datastream import StreamExecutionEnvironment, CheckpointingMode

from pravega_config import PravegaConfig
from pravega_writer import PravegaSink, PravegaWriterMode

CONTROLLER_URI = 'tcp://localhost:9090'
SCOPE = 'scope'
STREAM = 'stream'

env = StreamExecutionEnvironment.get_execution_environment()
env.set_parallelism(1)
env.enable_checkpointing(1000, CheckpointingMode.EXACTLY_ONCE)

pravega_config = PravegaConfig(uri=CONTROLLER_URI, scope=SCOPE)
pravega_sink = PravegaSink(stream=STREAM,
                           pravega_config=pravega_config,
                           writer_mode=PravegaWriterMode.ATLEAST_ONCE,
                           serialization_schema=SimpleStringSchema())

ds = env.from_collection(collection=['a', 'bb', 'ccc'],
                         type_info=Types.STRING())
ds.sink_to(pravega_sink)

env.execute("writer_test")

This simple test could run as expected with the connector jar attached either in Flink environment or manually linked in the run command.

[codecov]

Codecov Report

Merging #625 (7c3e8f5) into master (b7ba932) will increase coverage by 0.37%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #625      +/-   ##
============================================
+ Coverage     82.43%   82.80%   +0.37%     
- Complexity      497      531      +34     
============================================
  Files            49       50       +1     
  Lines          2420     2484      +64     
  Branches        210      214       +4     
============================================
+ Hits           1995     2057      +62     
  Misses          262      262              
- Partials        163      165       +2     

Impacted Files	Coverage Δ
...vega/connectors/flink/FlinkPravegaInputFormat.java	98.64% <0.00%> (-1.36%)	⬇️
...tors/flink/serialization/CheckpointSerializer.java	77.77% <0.00%> (ø)
...pravega/connectors/flink/ReaderCheckpointHook.java	95.40% <0.00%> (+3.73%)	⬆️

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[crazyzhou]

LGTM except one little word.

[crazyzhou]

I would suggest we leave this after we finished our SinkV2 work with Flink 1.15, so Close it for now. Please reopen this PR when that is available.