[GitHub] [beam] mattcasters commented on a change in pull request #15916: [BEAM-1857] Add Neo4jIO (initial code drop)

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mattcasters commented on a change in pull request #15916:
URL: https://github.com/apache/beam/pull/15916#discussion_r749182053



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File path: sdks/java/io/neo4j/src/main/java/org/apache/beam/sdk/io/neo4j/Neo4jIO.java
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@@ -0,0 +1,1346 @@
+/*
+ * 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.beam.sdk.io.neo4j;
+
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import java.io.Serializable;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import org.apache.beam.repackaged.core.org.apache.commons.lang3.StringUtils;
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.harness.JvmInitializer;
+import org.apache.beam.sdk.options.ValueProvider;
+import org.apache.beam.sdk.schemas.NoSuchSchemaException;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.SchemaRegistry;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.display.DisplayData;
+import org.apache.beam.sdk.transforms.display.HasDisplayData;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PDone;
+import org.apache.beam.sdk.values.TypeDescriptor;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.neo4j.driver.AuthTokens;
+import org.neo4j.driver.Config;
+import org.neo4j.driver.Driver;
+import org.neo4j.driver.GraphDatabase;
+import org.neo4j.driver.Logging;
+import org.neo4j.driver.Record;
+import org.neo4j.driver.Result;
+import org.neo4j.driver.Session;
+import org.neo4j.driver.SessionConfig;
+import org.neo4j.driver.TransactionConfig;
+import org.neo4j.driver.TransactionWork;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This is a Beam IO to read from, and write data to, Neo4j.
+ *
+ * <p>
+ *
+ * <p>
+ *
+ * <h3>Driver configuration</h3>
+ *
+ * <p>To read from or write to Neo4j you have to provide a {@link DriverConfiguration} using<br>
+ * 1. {@link DriverConfiguration#create()} (which must be {@link Serializable});<br>
+ * 2. or {@link DriverConfiguration#create(String, String, String)} (URL, username and password).
+ *
+ * <p>If you have trouble connecting to a Neo4j Aura database please try to disable a few security
+ * algorithms in your JVM. This makes sure that the right one is picked to connect:
+ *
+ * <p>
+ *
+ * <pre>{@code
+ * Security.setProperty(
+ *       "jdk.tls.disabledAlgorithms",
+ *       "SSLv3, RC4, DES, MD5withRSA, DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL");
+ * }</pre>
+ *
+ * <p>
+ *
+ * <p>
+ *
+ * <p>To execute this code on GCP Dataflow you can create a class which extends {@link
+ * JvmInitializer} and implement the {@link JvmInitializer#onStartup()} method. You need to annotate
+ * this new class with {@link com.google.auto.service.AutoService}
+ *
+ * <pre>{@code
+ * @AutoService(value = JvmInitializer.class)
+ * }</pre>
+ *
+ * <p>
+ *
+ * <h3>Reading from Neo4j</h3>
+ *
+ * <p>{@link Neo4jIO#readAll()} source returns a bounded collection of {@code OuptutT} as a {@code
+ * PCollection<OutputT>}. OutputT is the type returned by the provided {@link RowMapper}. It accepts
+ * parameters as input in the form of {@code ParameterT} as a {@code PCollection<ParameterT>}
+ *
+ * <p>The following example reads ages to return the IDs of Person nodes. It runs a Cypher query for
+ * each provided age.
+ *
+ * <p>The mapping {@link SerializableFunction} maps input values to each execution of the Cypher
+ * statement. In the function simply return a map containing the parameters you want to set.
+ *
+ * <p>The {@link RowMapper} converts output Neo4j {@link Record} values to the output of the source.
+ *
+ * <pre>{@code
+ * pipeline
+ *   .apply(Create.of(40, 50, 60))
+ *   .apply(Neo4jIO.<Integer, String>readAll()
+ *     .withDriverConfiguration(Neo4jIO.DriverConfiguration.create("neo4j://localhost:7687", "neo4j", "password"))
+ *     .withCypher("MATCH(n:Person) WHERE n.age = $age RETURN n.id")
+ *     .withReadTransaction()
+ *     .withCoder(StringUtf8Coder.of())
+ *     .withParametersFunction( age -> Collections.singletonMap( "age", age ))
+ *     .withRowMapper( record -> return record.get(0).asString() )
+ *   );
+ * }</pre>
+ *
+ * <h3>Writing to Neo4j</h3>
+ *
+ * <p>Neo4j sink supports writing data to a graph. It writes a {@link PCollection} to the graph by
+ * collecting a batch of rows after which all rows in this batch are written together to Neo4j. This
+ * is done using the {@link WriteUnwind} sink transform.
+ *
+ * <p>Like the source, to configure the sink, you have to provide a {@link DriverConfiguration}.
+ *
+ * <p>In the following example we'll merge a collection of {@link org.apache.beam.sdk.values.Row}
+ * into Person nodes. Since this is a Sink it has no output and as such no RowMapper is needed. The
+ * rows are being used as a container for the parameters of the Cypher statement. The used Cypher in
+ * question needs to be an UNWIND statement. Like in the read case, the parameters {@link
+ * SerializableFunction} converts parameter values to a {@link Map<String, Object>}. The difference
+ * here is that the resulting Map is stored in a {@link List} (containing maps) which in turn is
+ * stored in another Map under the name provided by the {@link
+ * WriteUnwind#withUnwindMapName(String)} method. All of this is handled automatically. You do need
+ * to provide the unwind map name so that you can reference that in the UNWIND statement.
+ *
+ * <p>
+ *
+ * <p>For example:
+ *
+ * <pre>{@code
+ * pipeline
+ *   .apply(...)
+ *   .apply(Neo4jIO.<Row>writeUnwind()
+ *      .withDriverConfiguration(Neo4jIO.DriverConfiguration.create("neo4j://localhost:7687", "neo4j", "password"))
+ *      .withUnwindMapName("rows")
+ *      .withCypher("UNWIND $rows AS row MERGE(n:Person { id : row.id } ) SET n.firstName = row.first, n.lastName = row.last")
+ *      .withParametersFunction( row -> ImmutableMap.of(
+ *        "id", row.getString("id),
+ *        "first", row.getString("firstName")
+ *        "last", row.getString("lastName")))
+ *    );
+ * }</pre>
+ */
+@Experimental(Experimental.Kind.SOURCE_SINK)
+public class Neo4jIO {
+
+  private static final Logger LOG = LoggerFactory.getLogger(Neo4jIO.class);
+
+  /**
+   * Read all rows using a Neo4j Cypher query.
+   *
+   * @param <ParameterT> Type of the data representing query parameters.
+   * @param <OutputT> Type of the data to be read.
+   */
+  public static <ParameterT, OutputT> ReadAll<ParameterT, OutputT> readAll() {
+    return new AutoValue_Neo4jIO_ReadAll.Builder<ParameterT, OutputT>()
+        .setFetchSize(ValueProvider.StaticValueProvider.of(Config.defaultConfig().fetchSize()))
+        .build();
+  }
+
+  /**
+   * Write all rows using a Neo4j Cypher UNWIND cypher statement. This sets a default batch batch
+   * size of 5000.
+   *
+   * @param <ParameterT> Type of the data representing query parameters.
+   */
+  public static <ParameterT> WriteUnwind<ParameterT> writeUnwind() {
+    return new AutoValue_Neo4jIO_WriteUnwind.Builder<ParameterT>()
+        .setBatchSize(ValueProvider.StaticValueProvider.of(5000L))
+        .build();
+  }
+
+  private static <ParameterT, OutputT> PCollection<OutputT> getOutputPCollection(
+      PCollection<ParameterT> input, DoFn<ParameterT, OutputT> writeFn, Coder<OutputT> coder) {
+    PCollection<OutputT> output = input.apply(ParDo.of(writeFn)).setCoder(coder);
+
+    try {
+      TypeDescriptor<OutputT> typeDesc = coder.getEncodedTypeDescriptor();
+      SchemaRegistry registry = input.getPipeline().getSchemaRegistry();
+      Schema schema = registry.getSchema(typeDesc);
+      output.setSchema(
+          schema,
+          typeDesc,
+          registry.getToRowFunction(typeDesc),
+          registry.getFromRowFunction(typeDesc));
+    } catch (NoSuchSchemaException e) {
+      // ignore
+    }
+    return output;
+  }
+
+  /**
+   * An interface used by {@link ReadAll} for converting each row of a Neo4j {@link Result} record
+   * {@link Record} into an element of the resulting {@link PCollection}.
+   */
+  @FunctionalInterface
+  public interface RowMapper<T> extends Serializable {
+    T mapRow(Record record) throws Exception;
+  }
+
+  /** This describes all the information needed to create a Neo4j {@link Session}. */
+  @AutoValue
+  public abstract static class DriverConfiguration implements Serializable {
+    public static DriverConfiguration create() {
+      return new AutoValue_Neo4jIO_DriverConfiguration.Builder().build();
+    }
+
+    public static DriverConfiguration create(String url, String username, String password) {
+      checkArgument(url != null, "url can not be null");
+      checkArgument(username != null, "username can not be null");
+      checkArgument(password != null, "password can not be null");
+      return new AutoValue_Neo4jIO_DriverConfiguration.Builder()
+          .build()
+          .withUrl(url)
+          .withUsername(username)
+          .withPassword(password);
+    }
+
+    abstract @Nullable ValueProvider<String> getUrl();

Review comment:
       Thanks for all the feedback and comments.  Unfortunately in this specific case the Neo4j Java driver makes a distinction between encrypted connections, non-encrypted connections and encrypted not specified (e.g. null in our case).  In that last case the driver figures things out automatically.   




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