``HealthCheckServlet`` requires that the servlet context has a ``HealthCheckRegistry`` named
``com.codahale.metrics.servlets.HealthCheckServlet.registry``. You can subclass
``HealthCheckServlet.ContextListener``, which will add a specific ``HealthCheckRegistry`` to the
servlet context.

An instance of ``ExecutorService`` can be provided via the servlet context using the name
``com.codahale.metrics.servlets.HealthCheckServlet.executor``; by default, no thread pool is used to
execute the health checks.

An instance of ``HealthCheckFilter`` can be provided via the servlet context using the name
``com.codahale.metrics.servlets.HealthCheckServlet.healthCheckFilter``; by default, no filtering is
enabled. The filter is used to determine which health checks to include in the health status.

An instance of ``ObjectMapper`` can be provided via the servlet context using the name
``com.codahale.metrics.servlets.HealthCheckServlet.mapper``; if none is provided, a default instance
will be used to convert the health check results to JSON.

Initialization Parameters

``HealthCheckServlet`` supports the following query parameters:

* ``httpStatusIndicator`` (``Boolean``): Determines whether the HTTP status code is used to
  determine whether the application is healthy; if not provided, it defaults to the value from the
  initialization parameter
* ``pretty`` (``Boolean``): Indicates whether the JSON response should be formatted; if
  ``"true"``, the JSON response will be formatted instead of condensed

.. _man-servlet-threaddump:

ThreadDumpServlet
=================

``ThreadDumpServlet`` responds to ``GET`` requests with a ``text/plain`` representation of all the live
threads in the JVM, their states, their stack traces, and the state of any locks they may be
waiting for.

Configuration
-------------

``ThreadDumpServlet`` supports the following configuration items.

Query Parameters

``MetricsServlet`` requires that the servlet context has a ``MetricRegistry`` named
``com.codahale.metrics.servlets.MetricsServlet.registry``. You can subclass
``MetricsServlet.ContextListener``, which will add a specific ``MetricRegistry`` to the servlet
context.

An instance of ``MetricFilter`` can be provided via the servlet context using the name
``com.codahale.metrics.servlets.MetricsServlet.metricFilter``; by default, no filtering is
enabled. The filter is used to determine which metrics to include in the JSON output.

Initialization Parameters

``MetricsServlet`` supports the following query parameters:

* ``pretty`` (``Boolean``): Determines whether the results are formatted; if not provided, this
  parameter defaults to ``"false"``.

.. _man-servlet-ping:

PingServlet
===========

``PingServlet`` responds to ``GET`` requests with a ``text/plain``/``200 OK`` response of ``pong``. This is
useful for determining liveness for load balancers, etc.

.. _man-servlet-cpu-profile:

CpuProfileServlet
=================

``CpuProfileServlet`` responds to ``GET`` requests with a ``pprof/raw``/``200 OK`` response containing the
results of CPU profiling.

Configuration
-------------

``CpuProfileServlet`` supports the following configuration items.

Query Parameters

public class MyMetricsServletContextListener extends MetricsServlet.ContextListener {

    public static final MetricRegistry METRIC_REGISTRY = new MetricRegistry();

    @Override
    protected MetricRegistry getMetricRegistry() {
        return METRIC_REGISTRY;
    }

}

public class MyHealthCheckServletContextListener extends HealthCheckServlet.ContextListener {

    public static final HealthCheckRegistry HEALTH_CHECK_REGISTRY = new HealthCheckRegistry();

    @Override
    protected HealthCheckRegistry getHealthCheckRegistry() {
        return HEALTH_CHECK_REGISTRY;
    }

}

<listener>
	<listener-class>com.example.MyMetricsServletContextListener</listener-class>
</listener>
<listener>
	<listener-class>com.example.MyHealthCheckServletContextListener</listener-class>
</listener>

<servlet>
	<servlet-name>metrics</servlet-name>
	<servlet-class>com.codahale.metrics.servlets.AdminServlet</servlet-class>
</servlet>
<servlet-mapping>
	<servlet-name>metrics</servlet-name>
	<url-pattern>/metrics/*</url-pattern>
</servlet-mapping>

``AdminServlet`` supports the following initialization parameters:

* ``metrics-enabled``: Determines whether the ``MetricsServlet`` is enabled and
  routable; if ``"false"``, the servlet endpoint will not be available via this servlet
* ``metrics-uri``: Specifies the URI for the ``MetricsServlet``; if omitted, the default
  (``/metrics``) will be used
* ``ping-enabled``: Determines whether the ``PingServlet`` is enabled and routable; if
  ``"false"``, the servlet endpoint will not be available via this servlet
* ``ping-uri``: Specifies the URI for the ``PingServlet``; if omitted, the default
  (``/ping``) will be used
* ``threads-enabled``: Determines whether the ``ThreadDumpServlet`` is enabled
  and routable; if ``"false"``, the servlet endpoint will not be available via this servlet
* ``threads-uri``: Specifies the URI for the ``ThreadDumpServlet``; if omitted, the default
  (``/threads``) will be used
* ``cpu-profile-enabled``: Determines whether the ``CpuProfileServlet`` is enabled and routable;
  if ``"false"``, the servlet endpoints will not be available via this servlet
* ``cpu-profile-uri``: Specifies the URIs for the ``CpuProfileServlet``; if omitted, the default
  (``/pprof``) will be used