Google dataflow: AvroIO read from file in google storage passed as runtime parameter - google-cloud-dataflow

Question

I want to read Avro files in my dataflow using java SDK 2
I have schedule my dataflow using cloud function which are triggered based on the files uploaded to the bucket.
Following is the code for options:
ValueProvider <String> getInputFile();
void setInputFile(ValueProvider<String> value);
I am trying to read this input file using following code:
PCollection<user> records = p.apply(
AvroIO.read(user.class)
.from(String.valueOf(options.getInputFile())));
I get following error while running the pipeline:
java.lang.IllegalArgumentException: Unable to find any files matching RuntimeValueProvider{propertyName=inputFile, default=gs://test_bucket/user.avro, value=null}
Same code works fine in case of TextIO.
How can we read Avro file which is uploaded for triggering cloud function which triggers the dataflow pipeline?

Answer 1

Please try ...from(options.getInputFile())) without converting it to a string.
For simplicity, you could even define your option as simple string:
String getInputFile();
void setInputFile(String value);

Answer 2

You need to use simply from(options.getInputFile()): AvroIO explicitly supports reading from a ValueProvider.
Currently the code is taking options.getInputFile() which is a ValueProvider, calling the JavatoString() function on it which gives a human-readable debug string "RuntimeValueProvider{propertyName=inputFile, default=gs://test_bucket/user.avro, value=null}" and passing that as a filename for AvroIO to read, and of course this string is not a valid filename, that's why the code currently doesn't work.
Also note that the whole point of ValueProvider is that it is placeholder for a value that is not known while constructing the pipeline and will be supplied later (potentially the pipeline will be executed several times, supplying different values) - so extracting the value of a ValueProvider at pipeline construction time is impossible by design, because there is no value. At runtime though (e.g. in a DoFn) you can extract the value by calling .get() on it.