[GitHub] [flink-connector-mongodb] rozza commented on a diff in pull request #1: [FLINK-6573][connectors/mongodb] Flink MongoDB Connector

[GitBox <gi...@apache.org>]

rozza commented on code in PR #1:
URL: https://github.com/apache/flink-connector-mongodb/pull/1#discussion_r1017963779


##########
flink-connector-mongodb/src/main/java/org/apache/flink/connector/mongodb/sink/writer/MongoWriter.java:
##########
@@ -0,0 +1,183 @@
+/*
+ * 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.flink.connector.mongodb.sink.writer;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.functions.util.ListCollector;
+import org.apache.flink.api.common.operators.MailboxExecutor;
+import org.apache.flink.api.common.serialization.SerializationSchema;
+import org.apache.flink.api.connector.sink2.Sink;
+import org.apache.flink.api.connector.sink2.SinkWriter;
+import org.apache.flink.connector.mongodb.common.config.MongoConnectionOptions;
+import org.apache.flink.connector.mongodb.sink.config.MongoWriteOptions;
+import org.apache.flink.connector.mongodb.sink.writer.context.DefaultMongoSinkContext;
+import org.apache.flink.connector.mongodb.sink.writer.context.MongoSinkContext;
+import org.apache.flink.connector.mongodb.sink.writer.serializer.MongoSerializationSchema;
+import org.apache.flink.metrics.groups.SinkWriterMetricGroup;
+import org.apache.flink.runtime.operators.util.metrics.CountingCollector;
+import org.apache.flink.util.Collector;
+import org.apache.flink.util.FlinkRuntimeException;
+
+import com.mongodb.MongoException;
+import com.mongodb.client.MongoClient;
+import com.mongodb.client.MongoClients;
+import com.mongodb.client.model.WriteModel;
+import org.bson.BsonDocument;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * This class is responsible for writing records to a MongoDB collection.
+ *
+ * @param <IN> The type of the input elements.
+ */
+@Internal
+public class MongoWriter<IN> implements SinkWriter<IN> {
+
+    private static final Logger LOG = LoggerFactory.getLogger(MongoWriter.class);
+
+    private final MongoConnectionOptions connectionOptions;
+    private final MongoWriteOptions writeOptions;
+    private final MongoSerializationSchema<IN> serializationSchema;
+    private final MongoSinkContext sinkContext;
+    private final MailboxExecutor mailboxExecutor;
+    private final boolean flushOnCheckpoint;
+    private final List<WriteModel<BsonDocument>> bulkRequests = new ArrayList<>();
+    private final Collector<WriteModel<BsonDocument>> collector;
+    private final MongoClient mongoClient;
+
+    private boolean checkpointInProgress = false;
+    private volatile long lastSendTime = 0L;
+    private volatile long ackTime = Long.MAX_VALUE;
+
+    public MongoWriter(
+            MongoConnectionOptions connectionOptions,
+            MongoWriteOptions writeOptions,
+            boolean flushOnCheckpoint,
+            Sink.InitContext initContext,
+            MongoSerializationSchema<IN> serializationSchema) {
+        this.connectionOptions = checkNotNull(connectionOptions);
+        this.writeOptions = checkNotNull(writeOptions);
+        this.serializationSchema = checkNotNull(serializationSchema);
+        this.flushOnCheckpoint = flushOnCheckpoint;
+
+        checkNotNull(initContext);
+        this.mailboxExecutor = checkNotNull(initContext.getMailboxExecutor());
+
+        SinkWriterMetricGroup metricGroup = checkNotNull(initContext.metricGroup());
+        metricGroup.setCurrentSendTimeGauge(() -> ackTime - lastSendTime);
+
+        this.collector =
+                new CountingCollector<>(
+                        new ListCollector<>(this.bulkRequests),
+                        metricGroup.getNumRecordsSendCounter());
+
+        // Initialize the serialization schema.
+        this.sinkContext = new DefaultMongoSinkContext(initContext, writeOptions);
+        try {
+            SerializationSchema.InitializationContext initializationContext =
+                    initContext.asSerializationSchemaInitializationContext();
+            serializationSchema.open(initializationContext, sinkContext, writeOptions);
+        } catch (Exception e) {
+            throw new FlinkRuntimeException("Failed to open the MongoEmitter", e);
+        }
+
+        // Initialize the mongo client.
+        this.mongoClient = MongoClients.create(connectionOptions.getUri());
+    }
+
+    @Override
+    public void write(IN element, Context context) throws IOException, InterruptedException {
+        // do not allow new bulk writes until all actions are flushed
+        while (checkpointInProgress) {
+            mailboxExecutor.yield();
+        }
+        collector.collect(serializationSchema.serialize(element, sinkContext));
+        if (isOverMaxBatchSizeLimit() || isOverMaxBatchIntervalLimit()) {
+            doBulkWrite();
+        }
+    }
+
+    @Override
+    public void flush(boolean endOfInput) throws IOException {
+        checkpointInProgress = true;
+        while (!bulkRequests.isEmpty() && (flushOnCheckpoint || endOfInput)) {
+            doBulkWrite();
+        }
+        checkpointInProgress = false;
+    }
+
+    @Override
+    public void close() {
+        mongoClient.close();
+    }
+
+    @VisibleForTesting
+    void doBulkWrite() throws IOException {
+        if (bulkRequests.isEmpty()) {
+            // no records to write
+            return;
+        }
+
+        int maxRetries = writeOptions.getMaxRetries();

Review Comment:
   Are all writes going to be idempotent? If not then rerunning multiple bulkwrite operations is likely to fail or produce multiple documents. This depends on the nature of the writes.
   
   The mongodb java driver supports: [retryable writes](https://www.mongodb.com/docs/manual/core/retryable-writes/) which has the ability to handle the retryability for transient networking errors.  In the MongoDB Kafka connector we removed the looping retry mechanism in favour of pushing users to set retryableWrites=true in the uri. See: [KAFKA-267](https://jira.mongodb.org/browse/KAFKA-267)



##########
flink-connector-mongodb/src/main/java/org/apache/flink/connector/mongodb/source/enumerator/splitter/MongoSplitVectorSplitter.java:
##########
@@ -0,0 +1,129 @@
+/*
+ * 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.flink.connector.mongodb.source.enumerator.splitter;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.configuration.MemorySize;
+import org.apache.flink.connector.mongodb.source.config.MongoReadOptions;
+import org.apache.flink.connector.mongodb.source.split.MongoScanSourceSplit;
+
+import com.mongodb.MongoCommandException;
+import com.mongodb.MongoNamespace;
+import com.mongodb.client.MongoClient;
+import org.apache.commons.collections.CollectionUtils;
+import org.bson.BsonArray;
+import org.bson.BsonDocument;
+import org.bson.BsonInt32;
+import org.bson.BsonValue;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.BSON_MAX_KEY;
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.BSON_MIN_KEY;
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.ERROR_MESSAGE_FIELD;
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.ID_FIELD;
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.ID_HINT;
+import static org.apache.flink.connector.mongodb.common.utils.MongoConstants.SPLIT_KEYS_FIELD;
+import static org.apache.flink.connector.mongodb.common.utils.MongoUtils.UNAUTHORIZED_ERROR;
+import static org.apache.flink.connector.mongodb.common.utils.MongoUtils.isCommandSucceed;
+import static org.apache.flink.connector.mongodb.common.utils.MongoUtils.splitVector;
+
+/**
+ * SplitVector Partitioner
+ *
+ * <p>Uses the SplitVector command to generate chunks for a collection. eg. <code>
+ * db.runCommand({splitVector:"inventory.products", keyPattern:{_id:1}, maxChunkSize:64})</code>
+ *
+ * <p>Requires splitVector privilege.
+ */
+@Internal
+public class MongoSplitVectorSplitter implements MongoSplitters.MongoSplitter {

Review Comment:
   Just an FYI - in the latest MongoDB Spark Connector we chose not add a SplitVector based partitioner due to the privilege requirements and because the API is marked as internal: See: [splitVector](https://www.mongodb.com/docs/manual/reference/command/splitVector/)



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