From 5dc241524c8e3b52d405280f45f58402a355a9cd Mon Sep 17 00:00:00 2001
From: Gray Watson <gray.github@mailgw.com>
Date: Tue, 21 Apr 2026 20:00:20 -0400
Subject: [PATCH] Added support for AWS_REGION env variable for testing
 purposes.

---
 .../persister/CloudWatchMetricsPersister.java | 21 ++++++++++++++++++-
 src/main/javadoc/doc-files/changelog.txt      |  3 +++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/j256/simplemetrics/persister/CloudWatchMetricsPersister.java b/src/main/java/com/j256/simplemetrics/persister/CloudWatchMetricsPersister.java
index 249c2c8..f78c2ad 100644
--- a/src/main/java/com/j256/simplemetrics/persister/CloudWatchMetricsPersister.java
+++ b/src/main/java/com/j256/simplemetrics/persister/CloudWatchMetricsPersister.java
@@ -20,7 +20,9 @@
 import com.j256.simplemetrics.metric.MetricValueDetails;
 import com.j256.simplemetrics.utils.MiscUtils;
 
+import software.amazon.awssdk.regions.Region;
 import software.amazon.awssdk.services.cloudwatch.CloudWatchClient;
+import software.amazon.awssdk.services.cloudwatch.CloudWatchClientBuilder;
 import software.amazon.awssdk.services.cloudwatch.model.Dimension;
 import software.amazon.awssdk.services.cloudwatch.model.MetricDatum;
 import software.amazon.awssdk.services.cloudwatch.model.MetricDatum.Builder;
@@ -50,6 +52,7 @@ public class CloudWatchMetricsPersister implements MetricDetailsPersister {
 	private static final String AWS_INSTANCE_INFO_IP = "169.254.169.254";
 	private static final String INSTANCE_ID_FETCH_PATH = "/latest/meta-data/instance-id";
 	private static final int AWS_CONNECT_TIMEOUT_MILLIS = 2000;
+	private static final String AWS_REGION_ENV_VAR = "AWS_REGION";
 
 	// makes sure that we are running in EC2 and extracts the instance-id name
 	private static final Pattern INSTANCE_ID_RESULT_REGEX = Pattern.compile("(?s).*Server: EC2ws.*\r?\n\r?\n(i-.*)");
@@ -58,6 +61,7 @@ public class CloudWatchMetricsPersister implements MetricDetailsPersister {
 	private String applicationName = "unknown";
 	private String nameSpacePrefix = DEFAULT_NAME_SPACE_PREFIX;
 	private boolean addInstanceData = true;
+	private String awsRegion;
 
 	private CloudWatchClient cloudWatchClient;
 	private static String instanceId;
@@ -104,7 +108,18 @@ public CloudWatchMetricsPersister(String applicationName, boolean addInstanceDat
 	 */
 	public void initialize() {
 		if (cloudWatchClient == null) {
-			cloudWatchClient = CloudWatchClient.builder().build();
+			CloudWatchClientBuilder builder = CloudWatchClient.builder();
+			if (awsRegion == null) {
+				awsRegion = System.getenv(AWS_REGION_ENV_VAR);
+			}
+			if (awsRegion != null) {
+				builder.region(Region.of(awsRegion));
+			}
+			try {
+				cloudWatchClient = builder.build();
+			} catch (Exception e) {
+				throw new RuntimeException("Could not build CloudWatch client", e);
+			}
 		}
 		if (addInstanceData) {
 			instanceId = downloadInstanceId(AWS_CONNECT_TIMEOUT_MILLIS);
@@ -184,6 +199,10 @@ public void setCloudWatchClient(CloudWatchClient cloudWatchClient) {
 		this.cloudWatchClient = cloudWatchClient;
 	}
 
+	public void setAwsRegion(String awsRegion) {
+		this.awsRegion = awsRegion;
+	}
+
 	/**
 	 * Return a map of metric name to associated data.
 	 */
diff --git a/src/main/javadoc/doc-files/changelog.txt b/src/main/javadoc/doc-files/changelog.txt
index 2e06897..74c3d85 100644
--- a/src/main/javadoc/doc-files/changelog.txt
+++ b/src/main/javadoc/doc-files/changelog.txt
@@ -1,3 +1,6 @@
+2.4: ?/?/2026
+	* Added support for AWS_REGION env variable for testing purposes. 
+
 2.3: 2/16/2026
 	* Had to re-release to fix some javadoc issues.  Grrrr.