I have a Kafka topic that contains json messages. Using Flink Python API I try to process this messages and store in parquet files in GCS.
Here is cleaned code snippet:
class Extract(MapFunction):
def map(self, value):
record = json.loads(value)
dt_object = datetime.strptime(record['ts'], "%Y-%m-%dT%H:%M:%SZ")
return Row(dt_object, record['event_id'])
<...>
events_schema = DataTypes.ROW([
DataTypes.FIELD("ts", DataTypes.TIMESTAMP()),
DataTypes.FIELD("event_id", DataTypes.STRING())
])
<...>
# Main job part
kafka_source = KafkaSource.builder() \
<...>
.build()
ds: DataStream = env.from_source(kafka_source, WatermarkStrategy.no_watermarks(), "Kafka Source")
mapped_data = ds.map(Extract(), Types.ROW([Types.SQL_TIMESTAMP(), Types.STRING()]))
sink = (FileSink
.for_bulk_format("gs://<my_events_path>",
ParquetBulkWriters.for_row_type(row_type=events_schema))
.with_output_file_config(
OutputFileConfig.builder()
.with_part_prefix("bids")
.with_part_suffix(".parquet")
.build())
.build())
mapped_data.sink_to(sink)
The problem is when I try to run this job I get an error:
Java.lang.ClassCastException: class java.sql.Timestamp cannot be cast to class java.time.LocalDateTime (java.sql.Timestamp is in module java.sql of loader 'platform'; java.time.LocalDateTime is in module java.base of loader 'bootstrap')
So the problem is that Types.SQL_TIMESTAMP()
and DataTypes.TIMESTAMP()
are not compatible when translated in corresponding Java classes. But I don't see any other option to "typify" my mapping transformation.
If instead of
mapped_data = ds.map(Extract(), Types.ROW([Types.SQL_TIMESTAMP(), Types.STRING()]))
I use this option
mapped_data = ds.map(Extract())
then I get another error:
java.lang.ClassCastException: class [B cannot be cast to class org.apache.flink.types.Row ([B is in module java.base of loader 'bootstrap'; org.apache.flink.types.Row is in unnamed module of loader 'app')
My question is can I save data containing timestamps in parquet format using Flink Python API?
So I managed to run this. There is a LocalTimeTypeInfo class for some reasons not listed under Types static methods.
So if I change
mapped_data = ds.map(Extract(), Types.ROW([Types.SQL_TIMESTAMP(), Types.STRING()]))
to
mapped_data = ds.map(Extract(), Types.ROW([LocalTimeTypeInfo(LocalTimeTypeInfo.TimeType.LOCAL_DATE_TIME), Types.STRING()]))
then it will work and create parquet files with timestamp columns. Still there is an issue because it uses deprecated INT96
type for physical representation but it works.