I'm new to Flink and in the process of trying to write a few operators and
tests for them. One of the issues I've ran into is "how do I properly set
up the dependencies for an operator". I've discovered the serialization
constraints and learned about the execution some model as I've started to
progress through it, but I'm still struggling to find an analog for
dependency injection in Flink.
I was experimenting with different ways to supply configuration for the
*Rich* functions to basically set themselves up and tear themselves down
with their dependencies on open/close. I wanted to basically "inject" a
dependency say like an HTTP client that caches, and then mock that
dependency for a local test instead of actually making HTTP calls. It
seemed like it could be done by getting and getting the correct
implementation types from the config using some custom injector type
(analogous to Spring or Guice dependency injection). I know I have to deal
serialization of the operators, which is why I was thinking I could do this
in open/close and have the magical injector be serializable (and possibly
be part of the config). This may or may not be a bad idea already, but bear
with me (and any feedback is very appreciated).
I was doing some local testing using StreamExecutionEnvironment, but wasn't
able to actually pass in configuration options to the local stream
execution.
I tried it these ways:
1. Create with a config
- StreamExecutionEnvironment.createLocalEnvironment(1, configuration);
2. Configure the created LocalStreamEnvironment
by env.getConfig().setGlobalJobParameters(configuration)
3. Configure thte DataStremSource<Integer>
by source.getExecutionConfig().setGlobalJobParameters(configuration)
4. Configure the SingleOutputStreamOperator
by mapped.getExecutionConfig().setGlobalJobParameters(configuration)
All 4 of those failed, so I felt like I am doing something wrong here, and
wanted to reach out.
Here is the example code where all of those tests failing:
import static org.assertj.core.api.Assertions.assertThat;
import org.apache.flink.api.common.functions.RichMapFunction;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.contrib.streaming.DataStreamUtils;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
import org.apache.flink.streaming.api.environment.LocalStreamEnvironment;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.junit.Test;
import java.util.Iterator;
public class FlinkInspection {
@Test
public void
issueWithLocalStreamEnvironmentCreateWithConfiguration() throws
Exception {
Configuration configuration = new Configuration();
configuration.setInteger("key", 10);
LocalStreamEnvironment env =
StreamExecutionEnvironment.createLocalEnvironment(1, configuration);
DataStreamSource<Integer> source = env.fromElements(1, 2);
SingleOutputStreamOperator<Integer> mapped = source.map(new
ConfigurationRetrievingOperator());
Iterator<Integer> collection = DataStreamUtils.collect(mapped);
env.execute();
assertThat(collection).containsExactlyInAnyOrder(10, 20);
}
@Test
public void
issueWithLocalStreamEnvironmentConfiguredWithWithConfiguration()
throws Exception {
Configuration configuration = new Configuration();
configuration.setInteger("key", 10);
LocalStreamEnvironment env =
StreamExecutionEnvironment.createLocalEnvironment(1);
env.getConfig().setGlobalJobParameters(configuration);
DataStreamSource<Integer> source = env.fromElements(1, 2);
SingleOutputStreamOperator<Integer> mapped = source.map(new
ConfigurationRetrievingOperator());
Iterator<Integer> collection = DataStreamUtils.collect(mapped);
env.execute();
assertThat(collection).containsExactlyInAnyOrder(10, 20);
}
@Test
public void
issueWithLocalStreamEnvironmentConfiguringDataStreamSource() throws
Exception {
LocalStreamEnvironment env =
StreamExecutionEnvironment.createLocalEnvironment(1);
DataStreamSource<Integer> source = env.fromElements(1, 2);
Configuration configuration = new Configuration();
configuration.setInteger("key", 10);
source.getExecutionConfig().setGlobalJobParameters(configuration);
SingleOutputStreamOperator<Integer> mapped = source.map(new
ConfigurationRetrievingOperator());
Iterator<Integer> collection = DataStreamUtils.collect(mapped);
env.execute();
assertThat(collection).containsExactlyInAnyOrder(10, 20);
}
@Test
public void
issueWithLocalStreamEnvironmentConfiguringDataStreamWithOperator()
throws Exception {
LocalStreamEnvironment env =
StreamExecutionEnvironment.createLocalEnvironment(1);
DataStreamSource<Integer> source = env.fromElements(1, 2);
Configuration configuration = new Configuration();
configuration.setInteger("key", 10);
SingleOutputStreamOperator<Integer> mapped = source.map(new
ConfigurationRetrievingOperator());
mapped.getExecutionConfig().setGlobalJobParameters(configuration);
Iterator<Integer> collection = DataStreamUtils.collect(mapped);
env.execute();
assertThat(collection).containsExactlyInAnyOrder(10, 20);
}
static class ConfigurationRetrievingOperator extends
RichMapFunction<Integer, Integer> {
private int factor = -1;
@Override
public Integer map(final Integer value) throws Exception {
return value * factor;
}
@Override
public void open(final Configuration parameters) throws Exception {
factor = parameters.getInteger("key", 0);
}
}
}
1. Any suggestions on how I should think about the dependency injection?
2. Are there ways to customize the Configuration that is passed into
Rich functions?
3. Is this an issue with LocalStreamEnvironment, or am I doing something
completely wrong?
