Make Docker JVM self-tuned and testcontainer tests improvements

.testcontainers.properties.template

@@ -0,0 +1,26 @@
+# Testcontainers reuse configuration
+# ------------------------------------
+# Place this file at: ~/.testcontainers.properties
+# (i.e., in your home directory, NOT the project directory)
+#
+# With reuse enabled, Testcontainers will leave containers running between
+# test runs rather than stopping and removing them when the JVM exits.
+# On the next run it detects that a matching container already exists and
+# connects to it instead of starting a new one.
+#
+# Effect on local dev:
+#   - Integration test startup drops from ~15-30 s (container start + Spring init)
+#     to ~2-3 s (Spring context only) after the first run.
+#   - MongoDB and ActiveMQ data persists between runs; run a clean start
+#     (`./gradlew integrationTest --rerun`) when you want a truly fresh state.
+#
+# This setting has NO effect in CI (containers always start fresh there because
+# the host is ephemeral). To explicitly disable reuse in CI, set the env var:
+#   TESTCONTAINERS_REUSE_ENABLE=false
+#
+# IMPORTANT: This file must also be created on each developer's machine.
+# Commit this template to the repo (e.g., as .testcontainers.properties.template)
+# so new developers know to copy it to ~/
+
+testcontainers.reuse.enable=true
+

CHANGELOG.md

@@ -11,6 +11,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 * Updated logging configuration to route application logs through async appender settings for improved runtime logging performance.
+* The service Docker image now uses JVM percentage-based heap sizing (`-XX:MaxRAMPercentage=75.0`, `-XX:InitialRAMPercentage=50.0`) 
+* instead of a fixed `-Xmx` value, so the heap adapts automatically when the container memory limit is changed without requiring an image rebuild.
+* Enabled G1GC explicitly (`-XX:+UseG1GC`) in the service container entrypoint for consistent garbage collection behaviour across deployments.
 
 ## [3.0.0] - 2025-11-06
 

docker/service/Dockerfile

@@ -20,5 +20,14 @@ COPY --from=package /home/gradle/service/build/libs/gp2gp-fhir-send-adaptor.jar
 
 USER 65534
 
-ENTRYPOINT ["java", "-XX:+PrintCommandLineFlags", "-cp", "/app/gp2gp-fhir-send-adaptor.jar", "-Dloader.main=uk.nhs.adaptors.gp2gp.Gp2gpApplication", "org.springframework.boot.loader.launch.PropertiesLauncher"]
+ENTRYPOINT ["java", \
+  "-XX:MaxRAMPercentage=75.0", \
+  "-XX:InitialRAMPercentage=50.0", \
+  "-XX:+UseG1GC", \
+  "-XX:+PrintCommandLineFlags", \
+  "-cp", "/app/gp2gp-fhir-send-adaptor.jar", \
+  "-Dloader.main=uk.nhs.adaptors.gp2gp.Gp2gpApplication", \
+  "org.springframework.boot.loader.launch.PropertiesLauncher"]
+
+
 

nhs-england-developer-information.md

@@ -8,6 +8,28 @@
 * JDK 21 — we develop the adaptor in Java with Spring Boot
 * Docker — we release the adaptor using Docker images on [Dockerhub](https://hub.docker.com/repository/docker/nhsdev/nia-gp2gp-adaptor)
 
+## One-time local dev setup
+
+### Enable Testcontainers container reuse (saves ~15–30 s per integration test run)
+
+Copy the template to your home directory:
+
+**macOS / Linux:**
+```bash
+cp .testcontainers.properties.template ~/.testcontainers.properties
+```
+
+This keeps MongoDB and ActiveMQ containers alive between runs so subsequent `./gradlew integrationTest`
+invocations skip the container start-up overhead.
+The property has no effect in CI (ephemeral hosts never have the file).
+
+To verify the setup is correct:
+
+**macOS / Linux:**
+```bash
+grep 'testcontainers.reuse.enable' ~/.testcontainers.properties
+```
+
 ## How to operate the adaptor
 
 The following sections describe how to run the adaptor for development and testing.

service/src/intTest/java/uk/nhs/adaptors/gp2gp/testcontainers/ActiveMqContainer.java

@@ -10,6 +10,12 @@ public final class ActiveMqContainer extends GenericContainer<ActiveMqContainer>
     private ActiveMqContainer() {
         super("docker-activemq:latest");
         addExposedPort(ACTIVEMQ_PORT);
+        // withReuse(true) keeps the container alive after the JVM exits so the next
+        // test run can reconnect to it instead of starting a new one (~15 s saving).
+        // Reuse is only activated when testcontainers.reuse.enable=true in
+        // ~/.testcontainers.properties (see .testcontainers.properties.template).
+        // In CI that property is absent so containers always start fresh.
+        withReuse(true);
     }
 
     public static ActiveMqContainer getInstance() {

service/src/intTest/java/uk/nhs/adaptors/gp2gp/testcontainers/MongoDbContainer.java

@@ -13,6 +13,12 @@ public final class MongoDbContainer extends GenericContainer<MongoDbContainer> {
     private MongoDbContainer() {
         super(DEFAULT_IMAGE_AND_TAG);
         addExposedPort(MONGODB_PORT);
+        // withReuse(true) keeps the container alive after the JVM exits so the next
+        // test run can reconnect to it instead of starting a new one (~15 s saving).
+        // Reuse is only activated when testcontainers.reuse.enable=true in
+        // ~/.testcontainers.properties (see .testcontainers.properties.template).
+        // In CI that property is absent so containers always start fresh.
+        withReuse(true);
     }
 
     public static MongoDbContainer getInstance() {

service/src/test/java/uk/nhs/adaptors/gp2gp/common/storage/S3StorageConnectorTest.java

@@ -38,7 +38,7 @@ class S3StorageConnectorTest {
     private static S3StorageConnector s3StorageConnector;
 
     @Container
-    private static final S3MockContainer S3_MOCK = new S3MockContainer("4.7.0");
+    private static final S3MockContainer S3_MOCK = new S3MockContainer("4.7.0").withReuse(true);
 
     private static S3Client s3Client;