cmathiesen commented on a change in pull request #678: Add Java code examples and update site docs URL: https://github.com/apache/incubator-iceberg/pull/678#discussion_r362411468
########## File path: examples/src/test/java/org/apache/iceberg/ConcurrencyTest.java ########## @@ -0,0 +1,130 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.iceberg; + +import java.io.File; +import java.io.IOException; +import java.nio.file.Files; +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import org.apache.hadoop.conf.Configuration; +import org.apache.iceberg.hadoop.HadoopTables; +import org.apache.iceberg.types.Types; +import org.apache.spark.sql.Dataset; +import org.apache.spark.sql.Row; +import org.apache.spark.sql.SparkSession; +import org.junit.After; +import org.junit.Before; +import org.junit.Test; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import static org.apache.iceberg.types.Types.NestedField.optional; + +/** + * This class tests how Iceberg handles concurrency when reading and writing at the same time + */ +public class ConcurrencyTest { + + private static final Logger log = LoggerFactory.getLogger(ConcurrencyTest.class); + + private Configuration conf = new Configuration(); + private Schema schema = new Schema( + optional(1, "key", Types.LongType.get()), + optional(2, "value", Types.StringType.get()) + ); + private SparkSession sparkReader; + private SparkSession sparkWriter; + private File tableLocation; + private Table table; + + private List<SimpleRecord> data = new ArrayList<>(); + + @Before + public void before() throws IOException { + tableLocation = Files.createTempDirectory("temp").toFile(); + + sparkReader = SparkSession.builder().master("local[2]").getOrCreate(); + sparkWriter = SparkSession.builder().master("local[2]").getOrCreate(); + + sparkReader.sparkContext().setLogLevel("WARN"); + sparkWriter.sparkContext().setLogLevel("WARN"); + + HadoopTables tables = new HadoopTables(conf); + table = tables.create(schema, tableLocation.toString()); + + for (int i = 0; i < 1000000; i++) { + data.add(new SimpleRecord(1, "bdp")); + } + + log.info("End of setup phase"); + } + + /** + * The test creates 500 read tasks and one really long write (writing 1 mil rows) + * and uses threading to call the tasks concurrently. + */ + @Test + public void writingAndReadingConcurrently() throws InterruptedException { + ExecutorService threadPool = Executors.newFixedThreadPool(5); + List<Callable<Void>> tasks = new ArrayList<>(); + + Callable<Void> write = () -> writeToTable(data); + tasks.add(write); + + for (int i = 0; i < 500; i++) { + Callable<Void> getReads = () -> readTable(); + tasks.add(getReads); + } + + threadPool.invokeAll(tasks); + threadPool.shutdown(); + + table.refresh(); + readTable(); + } + + private Void readTable() { + Dataset<Row> results = sparkReader.read() + .format("iceberg") + .load(tableLocation.toString()); + + log.info("" + results.count()); + return null; + } + private Void writeToTable(List<SimpleRecord> writeData) { Review comment: To do the threading for this test I'm using `ExecutorService` which requires a list of Callables which have to have some declared type that the task will return. And seeing as I don't need the result of either the write or the read (I decided to just log the output of the read at the end of the method) I need to use the Void wrapper type to create the Callable tasks ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
