add static factory for custom S3 endpoint in S3ObjectMonitor

service/src/main/java/org/whispersystems/textsecuregcm/configuration/MonitoredS3ObjectConfiguration.java

@@ -7,16 +7,19 @@
 
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import jakarta.validation.constraints.NotBlank;
+import java.net.URI;
 import java.time.Duration;
 import java.util.concurrent.ScheduledExecutorService;
 import org.whispersystems.textsecuregcm.s3.S3ObjectMonitor;
 import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
+import javax.annotation.Nullable;
 
 @JsonTypeName("default")
 public record MonitoredS3ObjectConfiguration(
     @NotBlank String s3Region,
     @NotBlank String s3Bucket,
     @NotBlank String objectKey,
+    @Nullable URI endpointOverride,
     Long maxSize,
     Duration refreshInterval) implements S3ObjectMonitorFactory {
 
@@ -36,6 +39,10 @@ public record MonitoredS3ObjectConfiguration(
   public S3ObjectMonitor build(final AwsCredentialsProvider awsCredentialsProvider,
       final ScheduledExecutorService refreshExecutorService) {
 
+    if (endpointOverride != null && !endpointOverride.toString().isEmpty()) {
+      return S3ObjectMonitor.createCustomS3(awsCredentialsProvider, endpointOverride, s3Region, s3Bucket, objectKey,
+          maxSize, refreshExecutorService, refreshInterval);
+    }
     return new S3ObjectMonitor(awsCredentialsProvider, s3Region, s3Bucket, objectKey, maxSize, refreshExecutorService,
         refreshInterval);
   }

service/src/main/java/org/whispersystems/textsecuregcm/s3/S3ObjectMonitor.java

@@ -8,6 +8,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.URI;
 import java.time.Duration;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
@@ -21,10 +22,13 @@
 import software.amazon.awssdk.core.ResponseInputStream;
 import software.amazon.awssdk.regions.Region;
 import software.amazon.awssdk.services.s3.S3Client;
+import software.amazon.awssdk.services.s3.S3ClientBuilder;
+import software.amazon.awssdk.services.s3.S3Configuration;
 import software.amazon.awssdk.services.s3.model.GetObjectRequest;
 import software.amazon.awssdk.services.s3.model.GetObjectResponse;
 import software.amazon.awssdk.services.s3.model.HeadObjectRequest;
 import software.amazon.awssdk.services.s3.model.HeadObjectResponse;
+import javax.annotation.Nullable;
 
 /**
  * An S3 object monitor watches a specific object in an S3 bucket and notifies a listener if that object changes.
@@ -65,6 +69,28 @@ public S3ObjectMonitor(
         refreshInterval);
   }
 
+  // allows specifying a custom S3 endpoint
+  static public S3ObjectMonitor createCustomS3(final AwsCredentialsProvider awsCredentialsProvider,
+      final URI s3Endpoint,
+      final String s3Region,
+      final String s3Bucket,
+      final String objectKey,
+      final long maxObjectSize,
+      final ScheduledExecutorService refreshExecutorService,
+      final Duration refreshInterval) {
+    final S3ClientBuilder s3ClientBuilder = S3Client.builder()
+        .region(Region.of(s3Region))
+        .credentialsProvider(awsCredentialsProvider)
+        .endpointOverride(s3Endpoint)
+        .serviceConfiguration(S3Configuration.builder()
+            .pathStyleAccessEnabled(true).build());
+    return new S3ObjectMonitor(s3ClientBuilder.build(), s3Bucket,
+        objectKey,
+        maxObjectSize,
+        refreshExecutorService,
+        refreshInterval);
+  }
+
   @VisibleForTesting
   S3ObjectMonitor(
       final S3Client s3Client,