Handle Docker 407 (Proxy Authentication Required) with clear error message

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/cache/CacheMeterBinderProvidersConfiguration.java

@@ -30,6 +30,7 @@
 import org.springframework.boot.actuate.metrics.cache.JCacheCacheMeterBinderProvider;
 import org.springframework.boot.actuate.metrics.cache.RedisCacheMeterBinderProvider;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.cache.caffeine.CaffeineCache;
 import org.springframework.cache.jcache.JCacheCache;
 import org.springframework.context.annotation.Bean;
@@ -83,6 +84,7 @@ HazelcastCacheMeterBinderProvider hazelcastCacheMeterBinderProvider() {
 	static class JCacheCacheMeterBinderProviderConfiguration {
 
 		@Bean
+		@ConditionalOnMissingBean(JCacheCacheMeterBinderProvider.class)
 		JCacheCacheMeterBinderProvider jCacheCacheMeterBinderProvider() {
 			return new JCacheCacheMeterBinderProvider();
 		}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/cache/JCacheCacheMeterBinderProviderBackOffTests.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.metrics.cache;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.metrics.cache.JCacheCacheMeterBinderProvider;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class JCacheCacheMeterBinderProviderBackOffTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+		.withConfiguration(AutoConfigurations.of(CacheMetricsAutoConfiguration.class));
+
+	@Test
+	void backsOffWhenUserProvidesProvider() {
+		JCacheCacheMeterBinderProvider custom = new JCacheCacheMeterBinderProvider();
+		this.contextRunner.withBean(JCacheCacheMeterBinderProvider.class, () -> custom).run((context) -> {
+			var bean = context.getBean(JCacheCacheMeterBinderProvider.class);
+			assertThat(bean).isSameAs(custom);
+		});
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/transport/HttpClientTransport.java

@@ -146,14 +146,35 @@ private Response execute(HttpUriRequest request) {
 		try {
 			ClassicHttpResponse response = this.client.executeOpen(this.host, request, null);
 			int statusCode = response.getCode();
+
 			if (statusCode >= 400 && statusCode <= 500) {
 				byte[] content = readContent(response);
-				response.close();
+
+				if (statusCode == 407) {
+					response.close();
+
+					String detail = null;
+					Message json = deserializeMessage(content);
+					if (json != null && org.springframework.util.StringUtils.hasText(json.getMessage())) {
+						detail = json.getMessage();
+					}
+					else {
+						detail = new String(content, java.nio.charset.StandardCharsets.UTF_8);
+					}
+
+					String msg = "Proxy authentication required for host: " + this.host.toHostString() + ", uri: "
+							+ request.getUri()
+							+ (org.springframework.util.StringUtils.hasText(detail) ? " - " + detail : "");
+
+					throw new ProxyAuthenticationException(msg);
+				}
+
 				Errors errors = (statusCode != 500) ? deserializeErrors(content) : null;
 				Message message = deserializeMessage(content);
 				throw new DockerEngineException(this.host.toHostString(), request.getUri(), statusCode,
 						response.getReasonPhrase(), errors, message);
 			}
+
 			return new HttpClientResponse(response);
 		}
 		catch (IOException | URISyntaxException ex) {

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/transport/ProxyAuthenticationException.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.buildpack.platform.docker.transport;
+
+public class ProxyAuthenticationException extends RuntimeException {
+
+	public ProxyAuthenticationException(String message) {
+		super(message);
+	}
+
+	public ProxyAuthenticationException(String message, Throwable cause) {
+		super(message, cause);
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/docker/transport/ProxyAuthenticationExceptionTests.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2012-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.buildpack.platform.docker.transport;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ProxyAuthenticationExceptionTests {
+
+	@Test
+	void constructsWithMessage() {
+		ProxyAuthenticationException ex = new ProxyAuthenticationException("Proxy auth failed");
+		assertThat(ex.getMessage()).isEqualTo("Proxy auth failed");
+	}
+
+	@Test
+	void constructsWithMessageAndCause() {
+		Exception cause = new Exception("boom");
+		ProxyAuthenticationException ex = new ProxyAuthenticationException("Proxy auth failed", cause);
+		assertThat(ex.getCause()).isSameAs(cause);
+		assertThat(ex.getMessage()).isEqualTo("Proxy auth failed");
+	}
+
+}