Fix bug in SslMeterBinder when binding without registered bundles

Before this commit the meter registries were derived from the created
gauges. If the SslMeterBinder has been bound to a MeterRegistry without
any bundles, then no gauges are created. If a SslBundle is then
dynamically added, onBundleChange is called with the new bundle, but the
list of meter registries is empty (because we have no gauges). The
effect is that the newly registered bundle has no metrics.

Closes gh-48180

Author: mhalbritter

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/ssl/SslMeterBinder.java

@@ -21,9 +21,7 @@
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Comparator;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -58,6 +56,8 @@ class SslMeterBinder implements MeterBinder {
 
 	private final BundleMetrics bundleMetrics = new BundleMetrics();
 
+	private final Set<MeterRegistry> boundMeterRegistries = ConcurrentHashMap.newKeySet();
+
 	SslMeterBinder(SslInfo sslInfo, SslBundles sslBundles) {
 		this(sslInfo, sslBundles, Clock.systemDefaultZone());
 	}
@@ -77,13 +77,14 @@ class SslMeterBinder implements MeterBinder {
 	private void onBundleChange(String bundleName) {
 		BundleInfo bundle = this.sslInfo.getBundle(bundleName);
 		this.bundleMetrics.updateBundle(bundle);
-		for (MeterRegistry meterRegistry : this.bundleMetrics.getMeterRegistries()) {
+		for (MeterRegistry meterRegistry : this.boundMeterRegistries) {
 			createOrUpdateBundleMetrics(meterRegistry, bundle);
 		}
 	}
 
 	@Override
 	public void bindTo(MeterRegistry meterRegistry) {
+		this.boundMeterRegistries.add(meterRegistry);
 		for (BundleInfo bundle : this.sslInfo.getBundles()) {
 			createOrUpdateBundleMetrics(meterRegistry, bundle);
 		}
@@ -138,18 +139,6 @@ MultiGauge getGauge(BundleInfo bundleInfo, MeterRegistry meterRegistry) {
 			return gauges.getGauge(meterRegistry);
 		}
 
-		/**
-		 * Returns all meter registries.
-		 * @return all meter registries
-		 */
-		Collection<MeterRegistry> getMeterRegistries() {
-			Set<MeterRegistry> result = new HashSet<>();
-			for (Gauges metrics : this.gauges.values()) {
-				result.addAll(metrics.getMeterRegistries());
-			}
-			return result;
-		}
-
 		/**
 		 * Updates the given bundle.
 		 * @param bundle the updated bundle
@@ -184,14 +173,6 @@ Gauges withBundle(BundleInfo bundle) {
 				return new Gauges(bundle, this.multiGauges);
 			}
 
-			/**
-			 * Returns all meter registries.
-			 * @return all meter registries
-			 */
-			Set<MeterRegistry> getMeterRegistries() {
-				return this.multiGauges.keySet();
-			}
-
 			private MultiGauge createGauge(MeterRegistry meterRegistry) {
 				return MultiGauge.builder(CHAIN_EXPIRY_METRIC_NAME)
 					.baseUnit("seconds")

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/ssl/SslMeterBinderTests.java

@@ -88,6 +88,14 @@ void shouldWatchUpdatesForBundlesRegisteredAfterConstruction() {
 			.hasDays(36889);
 	}
 
+	@Test
+	void shouldRegisterMetricsIfNoBundleExistsAtBindTime() {
+		DefaultSslBundleRegistry sslBundleRegistry = new DefaultSslBundleRegistry();
+		MeterRegistry meterRegistry = bindToRegistry(sslBundleRegistry);
+		sslBundleRegistry.registerBundle("dummy", SslBundle.of(createSslStoreBundle("classpath:test.p12")));
+		assertThat(meterRegistry.getMeters()).isNotEmpty();
+	}
+
 	private long findExpiryGauge(MeterRegistry meterRegistry, String chain, String certificateSerialNumber) {
 		return (long) meterRegistry.get("ssl.chain.expiry")
 			.tag("bundle", "test-0")