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HealthCheckServlet object mapper and status indicator (Jakarta EE)
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- Allow overriding the `ObjectMapper` instance used in `HealthCheckServlet` with the servlet attribute `io.dropwizard.metrics.servlets.HealthCheckServlet.mapper`
- Allow setting the HTTP status code used to indicate health to 200 (OK) with the servlet attribute `io.dropwizard.metrics.servlets.HealthCheckServlet.httpStatusIndicator`, or with the HTTP query parameter `httpStatusIndicator` per request

Refs #1821
Refs #1871
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@joschi
joschi committed Jan 24, 2024
1 parent 0aada3f commit 260dca9
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Showing 2 changed files with 116 additions and 96 deletions.
40 changes: 37 additions & 3 deletions ...ics-jakarta-servlets/src/main/java/io/dropwizard/metrics/servlets/HealthCheckServlet.java
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Original file line number Diff line number Diff line change
Expand Up @@ -45,11 +45,21 @@ protected HealthCheckFilter getHealthCheckFilter() {
return HealthCheckFilter.ALL;
}

/**
* @return the {@link ObjectMapper} that shall be used to render health checks,
* or {@code null} if the default object mapper should be used.
*/
protected ObjectMapper getObjectMapper() {
// don't use an object mapper by default
return null;
}

@Override
public void contextInitialized(ServletContextEvent event) {
final ServletContext context = event.getServletContext();
context.setAttribute(HEALTH_CHECK_REGISTRY, getHealthCheckRegistry());
context.setAttribute(HEALTH_CHECK_EXECUTOR, getExecutorService());
context.setAttribute(HEALTH_CHECK_MAPPER, getObjectMapper());
}

@Override
Expand All @@ -61,14 +71,18 @@ public void contextDestroyed(ServletContextEvent event) {
public static final String HEALTH_CHECK_REGISTRY = HealthCheckServlet.class.getCanonicalName() + ".registry";
public static final String HEALTH_CHECK_EXECUTOR = HealthCheckServlet.class.getCanonicalName() + ".executor";
public static final String HEALTH_CHECK_FILTER = HealthCheckServlet.class.getCanonicalName() + ".healthCheckFilter";
public static final String HEALTH_CHECK_MAPPER = HealthCheckServlet.class.getCanonicalName() + ".mapper";
public static final String HEALTH_CHECK_HTTP_STATUS_INDICATOR = HealthCheckServlet.class.getCanonicalName() + ".httpStatusIndicator";

private static final long serialVersionUID = -8432996484889177321L;
private static final String CONTENT_TYPE = "application/json";
private static final String HTTP_STATUS_INDICATOR_PARAM = "httpStatusIndicator";

private transient HealthCheckRegistry registry;
private transient ExecutorService executorService;
private transient HealthCheckFilter filter;
private transient ObjectMapper mapper;
private transient boolean httpStatusIndicator;

public HealthCheckServlet() {
}
Expand Down Expand Up @@ -96,7 +110,6 @@ public void init(ServletConfig config) throws ServletException {
this.executorService = (ExecutorService) executorAttr;
}


final Object filterAttr = context.getAttribute(HEALTH_CHECK_FILTER);
if (filterAttr instanceof HealthCheckFilter) {
filter = (HealthCheckFilter) filterAttr;
Expand All @@ -105,7 +118,20 @@ public void init(ServletConfig config) throws ServletException {
filter = HealthCheckFilter.ALL;
}

this.mapper = new ObjectMapper().registerModule(new HealthCheckModule());
final Object mapperAttr = context.getAttribute(HEALTH_CHECK_MAPPER);
if (mapperAttr instanceof ObjectMapper) {
this.mapper = (ObjectMapper) mapperAttr;
} else {
this.mapper = new ObjectMapper();
}
this.mapper.registerModule(new HealthCheckModule());

final Object httpStatusIndicatorAttr = context.getAttribute(HEALTH_CHECK_HTTP_STATUS_INDICATOR);
if (httpStatusIndicatorAttr instanceof Boolean) {
this.httpStatusIndicator = (Boolean) httpStatusIndicatorAttr;
} else {
this.httpStatusIndicator = true;
}
}

@Override
Expand All @@ -123,7 +149,10 @@ protected void doGet(HttpServletRequest req,
if (results.isEmpty()) {
resp.setStatus(HttpServletResponse.SC_NOT_IMPLEMENTED);
} else {
if (isAllHealthy(results)) {
final String reqParameter = req.getParameter(HTTP_STATUS_INDICATOR_PARAM);
final boolean httpStatusIndicatorParam = Boolean.parseBoolean(reqParameter);
final boolean useHttpStatusForHealthCheck = reqParameter == null ? httpStatusIndicator : httpStatusIndicatorParam;
if (!useHttpStatusForHealthCheck || isAllHealthy(results)) {
resp.setStatus(HttpServletResponse.SC_OK);
} else {
resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
Expand Down Expand Up @@ -158,4 +187,9 @@ private static boolean isAllHealthy(Map<String, HealthCheck.Result> results) {
}
return true;
}

// visible for testing
ObjectMapper getMapper() {
return mapper;
}
}
172 changes: 79 additions & 93 deletions ...jakarta-servlets/src/test/java/io/dropwizard/metrics/servlets/HealthCheckServletTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
import com.codahale.metrics.health.HealthCheck;
import com.codahale.metrics.health.HealthCheckFilter;
import com.codahale.metrics.health.HealthCheckRegistry;
import com.fasterxml.jackson.databind.ObjectMapper;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
Expand All @@ -15,6 +16,7 @@

import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

Expand Down Expand Up @@ -75,136 +77,79 @@ public void tearDown() {
public void returns501IfNoHealthChecksAreRegistered() throws Exception {
processRequest();

assertThat(response.getStatus())
.isEqualTo(501);
assertThat(response.getContent())
.isEqualTo("{}");
assertThat(response.get(HttpHeader.CONTENT_TYPE))
.isEqualTo("application/json");
assertThat(response.getStatus()).isEqualTo(501);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent()).isEqualTo("{}");
}

@Test
public void returnsA200IfAllHealthChecksAreHealthy() throws Exception {
registry.register("fun", new HealthCheck() {
@Override
protected Result check() {
return healthyResultUsingFixedClockWithMessage("whee");
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});
registry.register("fun", new TestHealthCheck(() -> healthyResultWithMessage("whee")));

processRequest();

assertThat(response.getStatus())
.isEqualTo(200);
assertThat(response.getStatus()).isEqualTo(200);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent())
.isEqualTo("{\"fun\":{\"healthy\":true,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" +
EXPECTED_TIMESTAMP +
"\"}}");
assertThat(response.get(HttpHeader.CONTENT_TYPE))
.isEqualTo("application/json");
}

@Test
public void returnsASubsetOfHealthChecksIfFiltered() throws Exception {
registry.register("fun", new HealthCheck() {
@Override
protected Result check() {
return healthyResultUsingFixedClockWithMessage("whee");
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});

registry.register("filtered", new HealthCheck() {
@Override
protected Result check() {
return Result.unhealthy("whee");
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});
registry.register("fun", new TestHealthCheck(() -> healthyResultWithMessage("whee")));
registry.register("filtered", new TestHealthCheck(() -> unhealthyResultWithMessage("whee")));

processRequest();

assertThat(response.getStatus())
.isEqualTo(200);
assertThat(response.getStatus()).isEqualTo(200);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent())
.isEqualTo("{\"fun\":{\"healthy\":true,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" +
EXPECTED_TIMESTAMP +
"\"}}");
assertThat(response.get(HttpHeader.CONTENT_TYPE))
.isEqualTo("application/json");
}

@Test
public void returnsA500IfAnyHealthChecksAreUnhealthy() throws Exception {
registry.register("fun", new HealthCheck() {
@Override
protected Result check() {
return healthyResultUsingFixedClockWithMessage("whee");
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});

registry.register("notFun", new HealthCheck() {
@Override
protected Result check() {
return Result.builder().usingClock(FIXED_CLOCK).unhealthy().withMessage("whee").build();
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});
registry.register("fun", new TestHealthCheck(() -> healthyResultWithMessage("whee")));
registry.register("notFun", new TestHealthCheck(() -> unhealthyResultWithMessage("whee")));

processRequest();

assertThat(response.getStatus())
.isEqualTo(500);
assertThat(response.getContent())
.contains(
assertThat(response.getStatus()).isEqualTo(500);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent()).contains(
"{\"fun\":{\"healthy\":true,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" + EXPECTED_TIMESTAMP + "\"}",
",\"notFun\":{\"healthy\":false,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" + EXPECTED_TIMESTAMP + "\"}}");
assertThat(response.get(HttpHeader.CONTENT_TYPE))
.isEqualTo("application/json");
}

@Test
public void returnsA200IfAnyHealthChecksAreUnhealthyAndHttpStatusIndicatorIsDisabled() throws Exception {
registry.register("fun", new TestHealthCheck(() -> healthyResultWithMessage("whee")));
registry.register("notFun", new TestHealthCheck(() -> unhealthyResultWithMessage("whee")));
request.setURI("/healthchecks?httpStatusIndicator=false");

processRequest();

assertThat(response.getStatus()).isEqualTo(200);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent()).contains(
"{\"fun\":{\"healthy\":true,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" + EXPECTED_TIMESTAMP + "\"}",
",\"notFun\":{\"healthy\":false,\"message\":\"whee\",\"duration\":0,\"timestamp\":\"" + EXPECTED_TIMESTAMP + "\"}}");
}

@Test
public void optionallyPrettyPrintsTheJson() throws Exception {
registry.register("fun", new HealthCheck() {
@Override
protected Result check() {
return healthyResultUsingFixedClockWithMessage("foo bar 123");
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
});
registry.register("fun", new TestHealthCheck(() -> healthyResultWithMessage("foo bar 123")));

request.setURI("/healthchecks?pretty=true");

processRequest();

assertThat(response.getStatus())
.isEqualTo(200);
assertThat(response.getStatus()).isEqualTo(200);
assertThat(response.get(HttpHeader.CONTENT_TYPE)).isEqualTo("application/json");
assertThat(response.getContent())
.isEqualTo(String.format("{%n" +
" \"fun\" : {%n" +
Expand All @@ -213,18 +158,24 @@ protected Clock clock() {
" \"duration\" : 0,%n" +
" \"timestamp\" : \"" + EXPECTED_TIMESTAMP + "\"" +
"%n }%n}"));
assertThat(response.get(HttpHeader.CONTENT_TYPE))
.isEqualTo("application/json");
}

private static HealthCheck.Result healthyResultUsingFixedClockWithMessage(String message) {
private static HealthCheck.Result healthyResultWithMessage(String message) {
return HealthCheck.Result.builder()
.healthy()
.withMessage(message)
.usingClock(FIXED_CLOCK)
.build();
}

private static HealthCheck.Result unhealthyResultWithMessage(String message) {
return HealthCheck.Result.builder()
.unhealthy()
.withMessage(message)
.usingClock(FIXED_CLOCK)
.build();
}

@Test
public void constructorWithRegistryAsArgumentIsUsedInPreferenceOverServletConfig() throws Exception {
final HealthCheckRegistry healthCheckRegistry = mock(HealthCheckRegistry.class);
Expand Down Expand Up @@ -266,4 +217,39 @@ public void constructorWithRegistryAsArgumentUsesServletConfigWhenNullButWrongTy
final io.dropwizard.metrics.servlets.HealthCheckServlet healthCheckServlet = new HealthCheckServlet(null);
healthCheckServlet.init(servletConfig);
}

@Test
public void constructorWithObjectMapperAsArgumentUsesServletConfigWhenNullButWrongTypeInContext() throws Exception {
final ServletContext servletContext = mock(ServletContext.class);
final ServletConfig servletConfig = mock(ServletConfig.class);
when(servletConfig.getServletContext()).thenReturn(servletContext);
when(servletContext.getAttribute(HealthCheckServlet.HEALTH_CHECK_REGISTRY)).thenReturn(registry);
when(servletContext.getAttribute(HealthCheckServlet.HEALTH_CHECK_MAPPER)).thenReturn("IRELLEVANT_STRING");

final HealthCheckServlet healthCheckServlet = new HealthCheckServlet(null);
healthCheckServlet.init(servletConfig);

assertThat(healthCheckServlet.getMapper())
.isNotNull()
.isInstanceOf(ObjectMapper.class);
}

static class TestHealthCheck extends HealthCheck {
private final Callable<Result> check;

public TestHealthCheck(Callable<Result> check) {
this.check = check;
}

@Override
protected Result check() throws Exception {
return check.call();
}

@Override
protected Clock clock() {
return FIXED_CLOCK;
}
}

}

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