Fix BatchCounter concurrency issue

services/submission/src/main/java/app/coronawarn/server/services/submission/config/SubmissionServiceConfig.java

@@ -116,13 +116,13 @@ public void setPath(String path) {
   }
 
   private static class Monitoring {
-    private Integer batchSize;
+    private Long batchSize;
 
-    public Integer getBatchSize() {
+    public Long getBatchSize() {
       return batchSize;
     }
 
-    public void setBatchSize(Integer batchSize) {
+    public void setBatchSize(Long batchSize) {
       this.batchSize = batchSize;
     }
   }
@@ -135,11 +135,11 @@ public void setMonitoring(Monitoring monitoring) {
     this.monitoring = monitoring;
   }
 
-  public Integer getMonitoringBatchSize() {
+  public Long getMonitoringBatchSize() {
     return this.monitoring.getBatchSize();
   }
 
-  public void setMonitoringBatchSize(Integer batchSize) {
+  public void setMonitoringBatchSize(Long batchSize) {
     this.monitoring.setBatchSize(batchSize);
   }
 }

services/submission/src/main/java/app/coronawarn/server/services/submission/monitoring/BatchCounter.java

@@ -22,6 +22,7 @@
 
 import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.MeterRegistry;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * Batch counter for counting requests for monitoring. Counts up in batches, given batch size. This way, single requests
@@ -33,11 +34,11 @@ public class BatchCounter {
   private static final String SUBMISSION_CONTROLLER_REQUESTS_COUNTER_DESCRIPTION
       = "Counts requests to the Submission Controller.";
 
-  private final int batchSize;
+  private final long batchSize;
   private final Counter counter;
-  private Double batch = 0.;
+  private final AtomicLong count = new AtomicLong(0L);
 
-  BatchCounter(MeterRegistry meterRegistry, int batchSize, String type) {
+  BatchCounter(MeterRegistry meterRegistry, long batchSize, String type) {
     this.batchSize = batchSize;
     counter = Counter.builder(SUBMISSION_CONTROLLER_REQUESTS_COUNTER_NAME)
         .tag("type", type)
@@ -50,11 +51,8 @@ public class BatchCounter {
    * counter is incremented.
    */
   public void increment() {
-    if (batch < batchSize) {
-      batch++;
-    } else {
-      counter.increment(batch);
-      batch = 1.;
+    if (0 == count.incrementAndGet() % batchSize) {
+      counter.increment(batchSize);
     }
   }
 }

services/submission/src/main/java/app/coronawarn/server/services/submission/monitoring/SubmissionControllerMonitor.java

@@ -38,7 +38,7 @@ public class SubmissionControllerMonitor {
 
   private final MeterRegistry meterRegistry;
 
-  private final Integer batchSize;
+  private final long batchSize;
   private BatchCounter requests;
   private BatchCounter realRequests;
   private BatchCounter fakeRequests;

services/submission/src/test/java/app/coronawarn/server/services/submission/monitoring/BatchCounterTest.java

@@ -0,0 +1,64 @@
+/*-
+ * ---license-start
+ * Corona-Warn-App
+ * ---
+ * Copyright (C) 2020 SAP SE and all other contributors
+ * ---
+ * Licensed 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.
+ * ---license-end
+ */
+
+package app.coronawarn.server.services.submission.monitoring;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.MeterRegistryMock;
+import java.util.stream.LongStream;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class BatchCounterTest {
+
+  private static final String COUNTER_TYPE = "FooCounter";
+  private MeterRegistry meterRegistry;
+  private Counter meterCounter;
+
+  @BeforeEach
+  void setUpCounter() {
+    meterCounter = mock(Counter.class);
+    meterRegistry = spy(new MeterRegistryMock(meterCounter));
+  }
+
+  @ParameterizedTest
+  @ValueSource(longs = {1L, 2L, 4L})
+  void incrementSubmittedOnceIfBatchSizeReached(long batchSize) {
+    BatchCounter batchCounter = new BatchCounter(meterRegistry, batchSize, COUNTER_TYPE);
+    LongStream.range(0, batchSize).forEach(__ -> batchCounter.increment());
+    verify(meterCounter, times(1)).increment(batchSize);
+  }
+
+  @ParameterizedTest
+  @ValueSource(longs = {2L, 4L, 7L})
+  void doesNotIncrementIfLesserThanBatchSize(long batchSize) {
+    BatchCounter batchCounter = new BatchCounter(meterRegistry, batchSize, COUNTER_TYPE);
+    LongStream.range(0, batchSize - 1).forEach(__ -> batchCounter.increment());
+    verify(meterCounter, never()).increment(batchSize);
+  }
+}

services/submission/src/test/java/io/micrometer/core/instrument/MeterRegistryMock.java

@@ -0,0 +1,40 @@
+/*-
+ * ---license-start
+ * Corona-Warn-App
+ * ---
+ * Copyright (C) 2020 SAP SE and all other contributors
+ * ---
+ * Licensed 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.
+ * ---license-end
+ */
+
+package io.micrometer.core.instrument;
+
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+
+/**
+ * Used to get access to the {@link Counter} instance in BatchCounterTest.
+ */
+public class MeterRegistryMock extends SimpleMeterRegistry {
+
+  final Counter counter;
+
+  public MeterRegistryMock(Counter counter) {
+    this.counter = counter;
+  }
+
+  @Override
+  Counter counter(Meter.Id id) {
+    return counter;
+  }
+}