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feat: Add Handlers.healthHandler
1 parent 3e09075 commit cbc58bd

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‎src/main/java/com/retailsvc/http/Handlers.java‎

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@@ -5,13 +5,19 @@
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import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
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import static java.net.HttpURLConnection.HTTP_NOT_FOUND;
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import static java.net.HttpURLConnection.HTTP_NO_CONTENT;
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import static java.net.HttpURLConnection.HTTP_OK;
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import static java.net.HttpURLConnection.HTTP_UNAVAILABLE;
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import static java.nio.charset.StandardCharsets.UTF_8;
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import com.retailsvc.http.internal.ClasspathResourceHandler;
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import com.retailsvc.http.internal.HealthRenderer;
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import com.retailsvc.http.internal.MethodLimitedHandler;
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import com.retailsvc.http.internal.ProblemDetailRenderer;
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import com.sun.net.httpserver.HttpHandler;
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import java.io.IOException;
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import java.util.List;
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import java.util.Objects;
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import java.util.function.Supplier;
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import java.util.stream.Collectors;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
@@ -67,6 +73,40 @@ public static HttpHandler aliveHandler() {
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});
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}
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/**
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* Health endpoint handler. Accepts GET and HEAD; returns 200 with {@code application/json} body
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* when the supplied probe reports {@code "Up"} (case-insensitive), and 503 with the same body
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* shape otherwise. A probe that throws a {@link RuntimeException} or returns {@code null} is
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* mapped to a {@code "Down"} outcome with an empty dependency list (and 503); the failure is
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* never propagated to the default exception handler.
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*
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* @param probe supplier of the current {@link HealthOutcome}
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*/
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public static HttpHandler healthHandler(Supplier<HealthOutcome> probe) {
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Objects.requireNonNull(probe, "probe");
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return new MethodLimitedHandler(
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exchange -> {
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try (exchange) {
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HealthOutcome outcome;
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try {
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HealthOutcome result = probe.get();
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if (result == null) {
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throw new IllegalStateException("Health probe returned null");
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}
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outcome = result;
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} catch (RuntimeException e) {
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LOG.warn("Health probe failed", e);
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outcome = new HealthOutcome("Down", List.of());
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}
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byte[] body = HealthRenderer.toJson(outcome).getBytes(UTF_8);
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int status = outcome.isUp() ? HTTP_OK : HTTP_UNAVAILABLE;
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exchange.getResponseHeaders().add("Content-Type", "application/json");
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exchange.sendResponseHeaders(status, body.length);
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exchange.getResponseBody().write(body);
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}
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});
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}
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/**
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* Serves a classpath resource. Content-Type is inferred from the file extension. The resource is
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* loaded eagerly; a missing resource fails immediately with {@link IllegalArgumentException}.

‎src/test/java/com/retailsvc/http/HealthHandlerTest.java‎

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package com.retailsvc.http;
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import static java.net.HttpURLConnection.HTTP_BAD_METHOD;
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import static java.net.HttpURLConnection.HTTP_OK;
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import static java.net.HttpURLConnection.HTTP_UNAVAILABLE;
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import static org.assertj.core.api.Assertions.assertThat;
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import static org.mockito.ArgumentMatchers.eq;
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import static org.mockito.Mockito.mock;
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import static org.mockito.Mockito.verify;
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import static org.mockito.Mockito.when;
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import com.sun.net.httpserver.Headers;
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import com.sun.net.httpserver.HttpExchange;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.util.List;
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import java.util.function.Supplier;
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import org.junit.jupiter.api.Test;
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class HealthHandlerTest {
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@Test
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void getReturns200AndJsonBodyWhenUp() throws IOException {
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HealthOutcome outcome = new HealthOutcome("Up", List.of(new Dependency("jdbc", "Up")));
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HttpExchange ex = newExchange("GET");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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ByteArrayOutputStream body = new ByteArrayOutputStream();
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when(ex.getResponseBody()).thenReturn(body);
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Handlers.healthHandler(() -> outcome).handle(ex);
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verify(ex).sendResponseHeaders(eq(HTTP_OK), eq((long) body.size()));
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assertThat(headers.getFirst("Content-Type")).isEqualTo("application/json");
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assertThat(body.toString())
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.isEqualTo("{\"outcome\":\"Up\",\"dependencies\":[{\"id\":\"jdbc\",\"status\":\"Up\"}]}");
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}
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@Test
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void getReturns200WithEmptyDependencyArrayWhenNoDeps() throws IOException {
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HttpExchange ex = newExchange("GET");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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ByteArrayOutputStream body = new ByteArrayOutputStream();
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when(ex.getResponseBody()).thenReturn(body);
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Handlers.healthHandler(() -> new HealthOutcome("Up", List.of())).handle(ex);
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verify(ex).sendResponseHeaders(eq(HTTP_OK), eq((long) body.size()));
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assertThat(body.toString()).isEqualTo("{\"outcome\":\"Up\",\"dependencies\":[]}");
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}
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@Test
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void getReturns503WhenDown() throws IOException {
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HealthOutcome outcome = new HealthOutcome("Down", List.of(new Dependency("jdbc", "Down")));
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HttpExchange ex = newExchange("GET");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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ByteArrayOutputStream body = new ByteArrayOutputStream();
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when(ex.getResponseBody()).thenReturn(body);
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Handlers.healthHandler(() -> outcome).handle(ex);
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verify(ex).sendResponseHeaders(eq(HTTP_UNAVAILABLE), eq((long) body.size()));
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assertThat(headers.getFirst("Content-Type")).isEqualTo("application/json");
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assertThat(body.toString()).contains("\"outcome\":\"Down\"");
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}
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@Test
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void headIsAccepted() throws IOException {
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HttpExchange ex = newExchange("HEAD");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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when(ex.getResponseBody()).thenReturn(new ByteArrayOutputStream());
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Handlers.healthHandler(() -> new HealthOutcome("Up", List.of())).handle(ex);
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verify(ex)
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.sendResponseHeaders(
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eq(HTTP_OK), eq((long) "{\"outcome\":\"Up\",\"dependencies\":[]}".length()));
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}
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@Test
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void postReturns405WithAllowHeader() throws IOException {
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HttpExchange ex = newExchange("POST");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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Handlers.healthHandler(() -> new HealthOutcome("Up", List.of())).handle(ex);
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verify(ex).sendResponseHeaders(HTTP_BAD_METHOD, -1);
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assertThat(headers.getFirst("Allow")).isEqualTo("GET, HEAD");
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}
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@Test
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void runtimeExceptionFromProbeMapsToDown503() throws IOException {
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HttpExchange ex = newExchange("GET");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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ByteArrayOutputStream body = new ByteArrayOutputStream();
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when(ex.getResponseBody()).thenReturn(body);
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Supplier<HealthOutcome> failing =
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() -> {
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throw new IllegalStateException("boom");
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};
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Handlers.healthHandler(failing).handle(ex);
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verify(ex).sendResponseHeaders(eq(HTTP_UNAVAILABLE), eq((long) body.size()));
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assertThat(body.toString()).isEqualTo("{\"outcome\":\"Down\",\"dependencies\":[]}");
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}
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@Test
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void nullReturnFromProbeMapsToDown503() throws IOException {
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HttpExchange ex = newExchange("GET");
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Headers headers = new Headers();
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when(ex.getResponseHeaders()).thenReturn(headers);
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ByteArrayOutputStream body = new ByteArrayOutputStream();
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when(ex.getResponseBody()).thenReturn(body);
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Handlers.healthHandler(() -> null).handle(ex);
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verify(ex).sendResponseHeaders(eq(HTTP_UNAVAILABLE), eq((long) body.size()));
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assertThat(body.toString()).isEqualTo("{\"outcome\":\"Down\",\"dependencies\":[]}");
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}
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private static HttpExchange newExchange(String method) {
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HttpExchange ex = mock(HttpExchange.class);
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when(ex.getRequestMethod()).thenReturn(method);
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when(ex.getResponseHeaders()).thenReturn(new Headers());
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return ex;
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}
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}

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