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HealthCheckServlet object mapper and status indicator #1871

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merged 4 commits into from
Apr 18, 2021
Merged

HealthCheckServlet object mapper and status indicator #1871

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d2bf481
HealthCheckServlet object mapper and status indicator
joschi Apr 15, 2021
3b2c6ce
Address SonarCloud violations
joschi Apr 15, 2021
220ebb7
Merge branch 'release/4.1.x' into pr-1821-http-status-code
joschi Apr 15, 2021
dabd78f
Merge branch 'release/4.1.x' into pr-1821-http-status-code
joschi Apr 18, 2021
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63 changes: 48 additions & 15 deletions metrics-servlets/src/main/java/com/codahale/metrics/servlets/HealthCheckServlet.java
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Original file line number Diff line number Diff line change
@@ -1,10 +1,11 @@
package com.codahale.metrics.servlets;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Map;
import java.util.SortedMap;
import java.util.concurrent.ExecutorService;
import com.codahale.metrics.health.HealthCheck;
import com.codahale.metrics.health.HealthCheckFilter;
import com.codahale.metrics.health.HealthCheckRegistry;
import com.codahale.metrics.json.HealthCheckModule;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
Expand All @@ -14,13 +15,11 @@
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.codahale.metrics.health.HealthCheck;
import com.codahale.metrics.health.HealthCheckFilter;
import com.codahale.metrics.health.HealthCheckRegistry;
import com.codahale.metrics.json.HealthCheckModule;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Map;
import java.util.SortedMap;
import java.util.concurrent.ExecutorService;

public class HealthCheckServlet extends HttpServlet {
public static abstract class ContextListener implements ServletContextListener {
Expand All @@ -46,11 +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 @@ -62,14 +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 @@ -97,7 +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 @@ -106,7 +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 @@ -124,7 +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 @@ -159,4 +187,9 @@ private static boolean isAllHealthy(Map<String, HealthCheck.Result> results) {
}
return true;
}

// visible for testing
ObjectMapper getMapper() {
return mapper;
}
}
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