Author: bdelacretaz
Date: Tue Aug 13 13:22:13 2013
New Revision: 1513475
URL: http://svn.apache.org/r1513475
Log:
SLING-2987 - health check docs tweaks
Modified:
sling/site/trunk/content/documentation/bundles/sling-health-check-tool.mdtext
Modified:
sling/site/trunk/content/documentation/bundles/sling-health-check-tool.mdtext
URL:
http://svn.apache.org/viewvc/sling/site/trunk/content/documentation/bundles/sling-health-check-tool.mdtext?rev=1513475&r1=1513474&r2=1513475&view=diff
==============================================================================
---
sling/site/trunk/content/documentation/bundles/sling-health-check-tool.mdtext
(original)
+++
sling/site/trunk/content/documentation/bundles/sling-health-check-tool.mdtext
Tue Aug 13 13:22:13 2013
@@ -1,10 +1,10 @@
Title: Sling Health Check Tool
-Based on simple _HealthCheck_ OSGi services, the Sling Health Check Tool ("hc"
in short form) is used to
+Based on simple `HealthCheck` OSGi services, the Sling Health Check Tool ("hc"
in short form) is used to
check the health of live Sling systems, based on inputs like JMX MBean
attribute values, OSGi framework
information, Sling requests status, etc.
-Health checks are easily extensible either by configuring the supplied default
_HealthCheck_ services, or
+Health checks are easily extensible either by configuring the supplied default
`HealthCheck` services, or
by implementing your own services.
Default rules are provided to check JMX MBeans, OSGi bundle states, disabling
of default Sling
@@ -12,34 +12,58 @@ accounts, JUnit tests results and the ou
The source code of the hc modules is at
[http://svn.apache.org/repos/asf/sling/trunk/contrib/extensions/healthcheck](http://svn.apache.org/repos/asf/sling/trunk/contrib/extensions/healthcheck).
-## What's a HealthCheck ?
+## What's a `HealthCheck` ?
+
+A `HealthCheck` is just an OSGi service that returns a `Result`.
+
+ public interface HealthCheck {
+
+ /** Execute this health check and return a {@link Result} */
+ public Result execute();
+
+ /** Additional (static) information about
+ * this check. {@link Constants} defines
+ * some well-known property names.
+ */
+ public Map<String, String> getInfo();
+ }
-A _HealthCheck_ is just an OSGi service that returns a _Result_.
The Result provides a _Status_ (OK, WARN, CRITICAL etc.) and a human-readable
log which provides additional info, including optional DEBUG messages
-that help troubleshooting. The Result log is not stricly tied to a logging
model, so HealthChecks are free to invent their own types of logging messages
+that help troubleshooting. The Result log is not stricly tied to a logging
model, so `HealthCheck`s are free to invent their own types of logging messages
if needed. See the `org.apache.sling.hc.api.Result` class in the for more
details.
-HealthCheck services can be selected for execution based on their _tags_. The
_HealthCheckFilter_ utility
-accepts positive and negative tag parameters, so that `-security,sling` for
example selects all HealthCheck
+`HealthCheck` services can be selected for execution based on their _tags_.
The `HealthCheckFilter` utility
+accepts positive and negative tag parameters, so that `-security,sling` for
example selects all `HealthCheck`
having the _sling_ tag but not the _security_ tag.
+## Health Check subsystem bundles
+The Health Check subsystem consists of the following bundles:
+
+* The only required bundle is `org.apache.sling.hc.api` which provides the API
and some utility classes.
+* `org.apache.sling.hc.healthchecks` provides default `HealthCheck` services,
described below.
+* `org.apache.sling.hc.webconsole` provides the Webconsole plugin described
below.
+* `org.apache.sling.hc.jmx` provides JMX MBeans to execute `HealthCheck`s.
+* `org.apache.sling.hc.samples` provides sample OSGi configurations that
demonstrate the default `HealthCheck`s. These configurations are provided as
Sling content, so the Sling Installer is required to activate them.
+
## Executing health checks
Besides executing them programatically, Health checks can be executed via a
webconsole plugin or via JMX,
see below for more details.
-## Default HealthCheck services and samples
+## Default `HealthCheck` services and samples
+
+A useful set of default `HealthCheck`s is provided by the
`org.apache.sling.hc.healthchecks` bundle.
-As of mid-August 2013, the `org.apache.sling.hc.samples` bundle provides OSGi
configurations that demonstrate the following HealthCheck services:
+The `org.apache.sling.hc.samples` bundle provides OSGi configurations that
demonstrate the following `HealthCheck` services:
* `JmxAttributeHealthCheck` checks the value of a single JMX attribute and
supports ranges like _between 12 and 42_.
* `SlingRequestStatusHealthCheck` checks the HTTP status of Sling requests.
* `ScriptableHealthCheck` evaluates an expression written in any scripting
language that Sling supports, and provides bindings to access JMX attributes
and OSGi bundles states.
* `DefaultLoginsHealthCheck` can be used to verify that the default Sling
logins fail.
- * `CompositeHealthCheck` executes a set of HealthCheck selected by tags,
useful to get higher-level management views.
+ * `CompositeHealthCheck` executes a set of `HealthCheck` selected by tags,
useful to get higher-level management views.
## Configuring health checks
-Health check services are created via OSGi configurations.
+`HealthCheck` services are created via OSGi configurations.
Here's a `ScriptableHealthCheck` example configuration provided by the
`org.apache.sling.hc.samples` bundle:
@@ -51,11 +75,12 @@ Here's a `ScriptableHealthCheck` example
expression = osgi.inactiveBundlesCount() == 0
language.extension = ecma
-Properties starting with the `hc.` prefix should be provided by all
HealthCheck services.
+Properties starting with the `hc.` prefix should be provided by all
`HealthCheck` services.
## Webconsole plugin
-A webconsole plugin at `/system/console/healthcheck` allows for executing
health checks, optionally selected
-based on their tags.
+If the `org.apache.sling.hc.webconsole` bundle is active, a webconsole plugin
+at `/system/console/healthcheck allows for executing health checks, optionally
selected
+based on their tags (positive and negative selection, see `HealthCheckFilter`
mention above).
The DEBUG logs of health checks can optionally be displayed, and an option
allows for showing only health
checks that have a non-OK status.
@@ -65,13 +90,14 @@ The screenshot below shows an example, a
## JMX access to health checks
-A JMX MBean is created for each HealthCheck, which gives access to the
`Result` and the log, as shown
-on the screenshot below.
+If the `org.apache.sling.hc.jmx` bundle is active, a JMX MBean is created for
each `HealthCheck`.
+
+The MBean gives access to the `Result` and the log, as shown on the screenshot
below.
-The MBean name defaults to the `hc.name` service property of the
_HealthCheck_, but if an
+The MBean name defaults to the `hc.name` service property of the
_`HealthCheck`_, but if an
`hc.mbean.name` property is provided it is used instead. That property can
include a a slash
(as in `composite/security`) to define the MBean service name, which by
default is _HealthCheck_.
The example configurations of the `org.apache.sling.hc.samples` bundle
demonstrate the various features.
-
+
\ No newline at end of file
