Put batch transmission logic in a separated class.

src/main/java/com/chavaillaz/appender/log4j/AbstractBatchLogDeliveryAppender.java

@@ -0,0 +1,89 @@
+package com.chavaillaz.appender.log4j;
+
+import static java.util.Collections.singletonList;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import com.chavaillaz.appender.LogConfiguration;
+import com.chavaillaz.appender.LogDelivery;
+import lombok.Getter;
+import lombok.extern.log4j.Log4j2;
+
+/**
+ * Abstract implementation of logs transmission by batches.
+ *
+ * @param <C> The configuration type
+ */
+@Log4j2
+public abstract class AbstractBatchLogDeliveryAppender<C extends LogConfiguration> implements LogDelivery {
+
+    /**
+     * The list of logs documents to be sent with the next transmission
+     */
+    private final List<Map<String, Object>> batch = new ArrayList<>();
+
+    /**
+     * The configuration of the logs transmission
+     */
+    @Getter
+    private final C configuration;
+
+    /**
+     * Creates a new logs delivery handler sending them by batches.
+     *
+     * @param configuration The configuration to use
+     */
+    protected AbstractBatchLogDeliveryAppender(C configuration) {
+        this.configuration = configuration;
+    }
+
+    @Override
+    public void send(Map<String, Object> document) {
+        send(singletonList(document));
+    }
+
+    @Override
+    public void send(List<Map<String, Object>> documents) {
+        if (documents != null && !documents.isEmpty()) {
+            stackAndSend(documents);
+        }
+    }
+
+    @Override
+    public synchronized void flush() {
+        if (!batch.isEmpty()) {
+            log.debug("Sending partial batch of {}/{}", batch.size(), configuration.getFlushThreshold());
+            sendBatch();
+        }
+    }
+
+    private synchronized void stackAndSend(List<Map<String, Object>> data) {
+        batch.addAll(data);
+        log.trace("Stacking batch {}/{}", batch.size(), configuration.getFlushThreshold());
+        if (batch.size() >= configuration.getFlushThreshold()) {
+            sendBatch();
+        }
+    }
+
+    private synchronized void sendBatch() {
+        if (!batch.isEmpty() && sendBulk(batch)) {
+            batch.clear();
+        }
+    }
+
+    /**
+     * Sends the given list of documents representing logs.
+     *
+     * @param documents The list of record data
+     * @return {@code true} if the transmission was successful, {@code false} otherwise
+     */
+    protected abstract boolean sendBulk(List<Map<String, Object>> documents);
+
+    @Override
+    public void close() {
+        sendBatch();
+    }
+
+}

src/main/java/com/chavaillaz/appender/log4j/elastic/ElasticsearchLogDelivery.java

@@ -3,32 +3,23 @@
 import static com.chavaillaz.appender.CommonUtils.createSSLContext;
 import static com.chavaillaz.appender.log4j.elastic.ElasticsearchUtils.createClient;
 import static java.time.OffsetDateTime.now;
-import static java.util.Collections.singletonList;
 import static org.apache.commons.lang3.StringUtils.isNotBlank;
 
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
 import co.elastic.clients.elasticsearch.ElasticsearchClient;
 import co.elastic.clients.elasticsearch.core.BulkRequest;
 import co.elastic.clients.elasticsearch.core.BulkResponse;
-import com.chavaillaz.appender.LogDelivery;
-import lombok.Getter;
+import com.chavaillaz.appender.log4j.AbstractBatchLogDeliveryAppender;
 import lombok.extern.log4j.Log4j2;
 
 /**
  * Implementation of logs transmission for Elasticsearch.
  */
 @Log4j2
-public class ElasticsearchLogDelivery implements LogDelivery {
+public class ElasticsearchLogDelivery extends AbstractBatchLogDeliveryAppender<ElasticsearchConfiguration> {
 
-    private final List<Map<String, Object>> batch = new ArrayList<>();
-
-    @Getter
-    private final ElasticsearchConfiguration configuration;
-
-    @Getter
     private final ElasticsearchClient client;
 
     /**
@@ -37,7 +28,7 @@ public class ElasticsearchLogDelivery implements LogDelivery {
      * @param configuration The configuration to use
      */
     public ElasticsearchLogDelivery(ElasticsearchConfiguration configuration) {
-        this.configuration = configuration;
+        super(configuration);
 
         if (isNotBlank(configuration.getApiKey())) {
             client = createClient(configuration.getUrl(), createSSLContext(), configuration.getApiKey());
@@ -47,46 +38,13 @@ public ElasticsearchLogDelivery(ElasticsearchConfiguration configuration) {
     }
 
     @Override
-    public void send(Map<String, Object> document) {
-        send(singletonList(document));
-    }
-
-    @Override
-    public void send(List<Map<String, Object>> documents) {
-        if (documents != null && !documents.isEmpty()) {
-            stackAndSend(documents);
-        }
-    }
-
-    @Override
-    public synchronized void flush() {
-        if (!batch.isEmpty()) {
-            log.debug("Sending partial batch of {}/{}", batch.size(), configuration.getFlushThreshold());
-            sendBatch();
-        }
-    }
-
-    private synchronized void stackAndSend(List<Map<String, Object>> data) {
-        batch.addAll(data);
-        log.trace("Batch size {}/{}", batch.size(), configuration.getFlushThreshold());
-        if (batch.size() >= configuration.getFlushThreshold()) {
-            sendBatch();
-        }
-    }
-
-    private synchronized void sendBatch() {
-        if (!batch.isEmpty() && sendBulk(batch)) {
-            batch.clear();
-        }
-    }
-
-    private boolean sendBulk(List<Map<String, Object>> documents) {
+    protected boolean sendBulk(List<Map<String, Object>> documents) {
         try {
             BulkRequest.Builder builder = new BulkRequest.Builder();
             for (Map<String, Object> document : documents) {
                 builder.operations(operation -> operation
                         .index(index -> index
-                                .index(configuration.generateIndexName(now()))
+                                .index(getConfiguration().generateIndexName(now()))
                                 .document(document)));
             }
 
@@ -104,7 +62,7 @@ private boolean sendBulk(List<Map<String, Object>> documents) {
     @Override
     public void close() {
         if (client != null) {
-            sendBatch();
+            super.close();
         }
     }