Add /healthz endpoint for health monitoring in S3Proxy

pom.xml

@@ -168,6 +168,26 @@
           </archive>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>pl.project13.maven</groupId>
+        <artifactId>git-commit-id-plugin</artifactId>
+        <version>5.0.0</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>revision</goal>
+            </goals>
+          </execution>
+        </executions>
+        <configuration>
+          <generateGitPropertiesFile>true</generateGitPropertiesFile>
+          <gitPropertiesFile>${project.build.outputDirectory}/git.properties</gitPropertiesFile>
+          <includeOnlyProperties>
+            <includeOnlyProperty>git.commit.id.abbrev</includeOnlyProperty>
+            <includeOnlyProperty>git.commit.id</includeOnlyProperty>
+          </includeOnlyProperties>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>

src/main/java/org/gaul/s3proxy/S3ProxyHandler.java

@@ -41,6 +41,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Properties;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TimeZone;
@@ -58,6 +59,7 @@
 import javax.xml.stream.XMLStreamWriter;
 
 import com.fasterxml.jackson.core.JsonParseException;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.google.common.base.CharMatcher;
 import com.google.common.base.Splitter;
@@ -293,6 +295,13 @@ public final void doHandle(HttpServletRequest baseRequest,
         String uri = request.getRequestURI();
         String originalUri = request.getRequestURI();
 
+        String healthzUri = servicePath.isEmpty() ? "/healthz" :
+                servicePath + "/healthz";
+        if (healthzUri.equals(uri) && "GET".equalsIgnoreCase(method)) {
+            handleStatuszRequest(response);
+            return;
+        }
+
         if (!this.servicePath.isEmpty()) {
             if (uri.length() > this.servicePath.length()) {
                 uri = uri.substring(this.servicePath.length());
@@ -2030,6 +2039,55 @@ private void handlePutBlob(HttpServletRequest request,
         response.addHeader(HttpHeaders.ETAG, maybeQuoteETag(eTag));
     }
 
+    private void handleStatuszRequest(HttpServletResponse response)
+            throws IOException {
+        response.setStatus(HttpServletResponse.SC_OK);
+        response.setContentType("application/json");
+        response.setCharacterEncoding(UTF_8);
+
+        var statusBody = ImmutableMap.of("gitHash", StatusMetadata.INSTANCE.gitHash);
+        String versionInfo = StatusMetadata.JSON_MAPPER.writeValueAsString(statusBody);
+
+        try (PrintWriter writer = response.getWriter()) {
+            writer.write(versionInfo);
+            writer.flush();
+        }
+    }
+
+    private static final class StatusMetadata {
+        private static final ObjectMapper JSON_MAPPER = new ObjectMapper();
+        private static final StatusMetadata INSTANCE = StatusMetadata.load();
+        private static final String UNKNOWN_VALUE = "unknown";
+        private final String gitHash;
+
+        private StatusMetadata(String gitHash) {
+            this.gitHash = gitHash;
+        }
+
+        static StatusMetadata load() {
+            String gitHash = loadGitHash();
+            return new StatusMetadata(gitHash);
+        }
+
+        private static String loadGitHash() {
+            try (InputStream stream = S3ProxyHandler.class.getClassLoader()
+                    .getResourceAsStream("git.properties")) {
+                if (stream == null) {
+                    return UNKNOWN_VALUE;
+                }
+                Properties properties = new Properties();
+                properties.load(stream);
+                return Optional.ofNullable(
+                        properties.getProperty("git.commit.id.abbrev"))
+                        .orElseGet(() -> properties.getProperty("git.commit.id",
+                                UNKNOWN_VALUE));
+            } catch (IOException ioe) {
+                logger.debug("Unable to load git.properties", ioe);
+                return UNKNOWN_VALUE;
+            }
+        }
+    }
+
     private void handlePostBlob(HttpServletRequest request,
             HttpServletResponse response, InputStream is, BlobStore blobStore,
             String containerName)

src/test/java/org/gaul/s3proxy/AwsSdkAnonymousTest.java

@@ -19,7 +19,9 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.io.InputStream;
+import java.net.HttpURLConnection;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
 import java.util.Random;
 
 import com.amazonaws.SDKGlobalConfiguration;
@@ -50,6 +52,7 @@ public final class AwsSdkAnonymousTest {
     private static final ByteSource BYTE_SOURCE = ByteSource.wrap(new byte[1]);
 
     private URI s3Endpoint;
+    private URI httpEndpoint;
     private EndpointConfiguration s3EndpointConfig;
     private S3Proxy s3Proxy;
     private BlobStoreContext context;
@@ -66,6 +69,7 @@ public void setUp() throws Exception {
         awsCreds = new AnonymousAWSCredentials();
         context = info.getBlobStore().getContext();
         s3Proxy = info.getS3Proxy();
+        httpEndpoint = info.getEndpoint();
         s3Endpoint = info.getSecureEndpoint();
         servicePath = info.getServicePath();
         s3EndpointConfig = new EndpointConfiguration(
@@ -128,6 +132,31 @@ public void testAwsV4SignatureChunkedAnonymous() throws Exception {
         }
     }
 
+    @Test
+    public void testHealthzEndpoint() throws Exception {
+        URI baseUri = httpEndpoint != null ? httpEndpoint : s3Endpoint;
+        String path = (servicePath == null ? "" : servicePath) + "/healthz";
+        URI healthzUri = new URI(baseUri.getScheme(), baseUri.getUserInfo(),
+                baseUri.getHost(), baseUri.getPort(), path,
+                baseUri.getQuery(), baseUri.getFragment());
+
+        HttpURLConnection connection =
+                (HttpURLConnection) healthzUri.toURL().openConnection();
+        connection.setRequestMethod("GET");
+
+        assertThat(connection.getResponseCode()).isEqualTo(200);
+
+        String body;
+        try (InputStream stream = connection.getInputStream()) {
+            body = new String(stream.readAllBytes(), StandardCharsets.UTF_8);
+        } finally {
+            connection.disconnect();
+        }
+
+        assertThat(body).contains("\"gitHash\":\"");
+        assertThat(body).startsWith("{").endsWith("}");
+    }
+
     private static String createRandomContainerName() {
         return "s3proxy-" + new Random().nextInt(Integer.MAX_VALUE);
     }