Made new features thread safe

Author: lksfrnz

src/main/java/software/amazon/cloudwatchlogs/emf/logger/MetricsLogger.java

@@ -359,6 +359,7 @@ public MetricsLogger putMetric(String key, double value, AggregationType aggrega
      * @throws InvalidMetricException if the metric is invalid
      */
     public MetricsLogger setMetric(String key, Metric value) throws InvalidMetricException {
+        rwl.readLock().lock();
         try {
             this.context.setMetric(key, value);
             return this;

src/main/java/software/amazon/cloudwatchlogs/emf/model/HistogramMetric.java

@@ -95,22 +95,37 @@ public HistogramMetricBuilder() {
 
         @Override
         public Histogram getValues() {
-            return values.reduce();
+            rwl.readLock().lock();
+            try {
+                return values.reduce();
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         @Override
         public HistogramMetricBuilder addValue(double value) {
-            this.values.addValue(value);
-            return this;
+            rwl.readLock().lock();
+            try {
+                values.addValue(value);
+                return this;
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         @Override
         public HistogramMetric build() {
-            values.reduce();
-            if (name == null) {
-                return new HistogramMetric(unit, storageResolution, values);
+            rwl.writeLock().lock();
+            try {
+                values.reduce();
+                if (name == null) {
+                    return new HistogramMetric(unit, storageResolution, values);
+                }
+                return new HistogramMetric(name, unit, storageResolution, values);
+            } finally {
+                rwl.writeLock().unlock();
             }
-            return new HistogramMetric(name, unit, storageResolution, values);
         }
     }
 }

src/main/java/software/amazon/cloudwatchlogs/emf/model/Metric.java

@@ -22,6 +22,7 @@
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 import java.util.Queue;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NonNull;
@@ -78,6 +79,14 @@ protected Object getFormattedValues() {
 
     public abstract static class MetricBuilder<V, T extends MetricBuilder<V, T>> extends Metric<V> {
 
+        /**
+         * This lock is used to create an internal sync context for build() method in multi-threaded
+         * situations. build() acquires write lock, other methods (accessing mutable shared data))
+         * acquires read lock. This makes sure build() is executed exclusively, while other methods
+         * can be executed concurrently.
+         */
+        @JsonIgnore final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
+
         protected abstract T getThis();
 
         /**
@@ -95,18 +104,33 @@ public abstract static class MetricBuilder<V, T extends MetricBuilder<V, T>> ext
         abstract Metric<V> build();
 
         protected T name(@NonNull String name) {
-            this.name = name;
-            return getThis();
+            rwl.readLock().lock();
+            try {
+                this.name = name;
+                return getThis();
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         public T unit(Unit unit) {
-            this.unit = unit;
-            return getThis();
+            rwl.readLock().lock();
+            try {
+                this.unit = unit;
+                return getThis();
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         public T storageResolution(StorageResolution storageResolution) {
-            this.storageResolution = storageResolution;
-            return getThis();
+            rwl.readLock().lock();
+            try {
+                this.storageResolution = storageResolution;
+                return getThis();
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         @Override

src/main/java/software/amazon/cloudwatchlogs/emf/model/MetricDefinition.java

@@ -118,21 +118,36 @@ public MetricDefinitionBuilder() {
 
         @Override
         public MetricDefinitionBuilder addValue(double value) {
-            this.values.add(value);
-            return this;
+            rwl.readLock().lock();
+            try {
+                this.values.add(value);
+                return this;
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         public MetricDefinitionBuilder values(@NonNull List<Double> values) {
-            this.values = values;
-            return this;
+            rwl.readLock().lock();
+            try {
+                this.values = values;
+                return this;
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         @Override
         public MetricDefinition build() {
-            if (name == null) {
-                return new MetricDefinition(unit, storageResolution, values);
+            rwl.writeLock().lock();
+            try {
+                if (name == null) {
+                    return new MetricDefinition(unit, storageResolution, values);
+                }
+                return new MetricDefinition(name, unit, storageResolution, values);
+            } finally {
+                rwl.writeLock().unlock();
             }
-            return new MetricDefinition(name, unit, storageResolution, values);
         }
     }
 }

src/main/java/software/amazon/cloudwatchlogs/emf/model/StatisticSet.java

@@ -89,21 +89,36 @@ public StatisticSetBuilder() {
 
         @Override
         public StatisticSetBuilder addValue(double value) {
-            this.values.addValue(value);
-            return this;
+            rwl.readLock().lock();
+            try {
+                this.values.addValue(value);
+                return this;
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
-        public StatisticSetBuilder values(@NonNull Statistics values) {
-            this.values = values;
-            return this;
+        StatisticSetBuilder values(@NonNull Statistics values) {
+            rwl.readLock().lock();
+            try {
+                this.values = values;
+                return this;
+            } finally {
+                rwl.readLock().unlock();
+            }
         }
 
         @Override
         public StatisticSet build() {
-            if (name == null) {
-                return new StatisticSet(unit, storageResolution, values);
+            rwl.writeLock().lock();
+            try {
+                if (name == null) {
+                    return new StatisticSet(unit, storageResolution, values);
+                }
+                return new StatisticSet(name, unit, storageResolution, values);
+            } finally {
+                rwl.writeLock().unlock();
             }
-            return new StatisticSet(name, unit, storageResolution, values);
         }
     }
 }