Number of input rows in spark structured streaming with custom sink - apache-spark

Question

I'm using a custom sink in structured stream (spark 2.2.0) and noticed that spark produces incorrect metrics for number of input rows - it's always zero.
My stream construction:
StreamingQuery writeStream = session
.readStream()
.schema(RecordSchema.fromClass(TestRecord.class))
.option(OPTION_KEY_DELIMITER, OPTION_VALUE_DELIMITER_TAB)
.option(OPTION_KEY_QUOTE, OPTION_VALUE_QUOTATION_OFF)
.csv(s3Path.toString())
.as(Encoders.bean(TestRecord.class))
.flatMap(
((FlatMapFunction<TestRecord, TestOutputRecord>) (u) -> {
List<TestOutputRecord> list = new ArrayList<>();
try {
TestOutputRecord result = transformer.convert(u);
list.add(result);
} catch (Throwable t) {
System.err.println("Failed to convert a record");
t.printStackTrace();
}
return list.iterator();
}),
Encoders.bean(TestOutputRecord.class))
.map(new DataReinforcementMapFunction<>(), Encoders.bean(TestOutputRecord.clazz))
.writeStream()
.trigger(Trigger.ProcessingTime(WRITE_FREQUENCY, TimeUnit.SECONDS))
.format(MY_WRITER_FORMAT)
.outputMode(OutputMode.Append())
.queryName("custom-sink-stream")
.start();
writeStream.processAllAvailable();
writeStream.stop();
Logs:
Streaming query made progress: {
"id" : "a8a7fbc2-0f06-4197-a99a-114abae24964",
"runId" : "bebc8a0c-d3b2-4fd6-8710-78223a88edc7",
"name" : "custom-sink-stream",
"timestamp" : "2018-01-25T18:39:52.949Z",
"numInputRows" : 0,
"inputRowsPerSecond" : 0.0,
"processedRowsPerSecond" : 0.0,
"durationMs" : {
"getOffset" : 781,
"triggerExecution" : 781
},
"stateOperators" : [ ],
"sources" : [ {
"description" : "FileStreamSource[s3n://test-bucket/test]",
"startOffset" : {
"logOffset" : 0
},
"endOffset" : {
"logOffset" : 0
},
"numInputRows" : 0,
"inputRowsPerSecond" : 0.0,
"processedRowsPerSecond" : 0.0
} ],
"sink" : {
"description" : "com.mycompany.spark.MySink#f82a99"
}
}
Do I have to populate any metrics in my custom sink to be able to track progress? Or could it be a problem in FileStreamSource when it reads from s3 bucket?

Answer 1

The problem was related to using dataset.rdd in my custom sink that creates a new plan so that StreamExecution doesn't know about it and therefore is not able to get metrics.
Replacing data.rdd.mapPartitions with data.queryExecution.toRdd.mapPartitions fixes the issue.