org.apache.ambari.server.state.services

Class MetricsRetrievalService

java.lang.Object

com.google.common.util.concurrent.AbstractService

org.apache.ambari.server.state.services.MetricsRetrievalService

All Implemented Interfaces:

com.google.common.util.concurrent.Service

public class MetricsRetrievalService
extends com.google.common.util.concurrent.AbstractService

The MetricsRetrievalService is used as a headless, autonomous service which encapsulates:

• An ExecutorService for fulfilling remote metric URL requests
• A cache for JMX metrics
• A cache for REST metrics

Classes can inject an instance of this service in order to gain access to its caches and request mechanism.

Callers must submit a request to the service in order to reach out and pull in remote metric data. Otherwise, the cache will never be populated. On the first usage of this service, the cache will always be empty. On every subsequent request, the data from the prior invocation of submitRequest(MetricSourceType, StreamProvider, String) will be available.

Metric data is cached temporarily and is controlled by Configuration.getMetricsServiceCacheTimeout().

In order to control throttling requests to the same endpoint, Configuration.isMetricsServiceRequestTTLCacheEnabled() can be enabled to allow for a fixed interval of time to pass between requests.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MetricsRetrievalService.MetricSourceType The type of web service hosting the metrics.

Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service

com.google.common.util.concurrent.Service.Listener, com.google.common.util.concurrent.Service.State

Constructor Summary

Constructors

Constructor and Description
MetricsRetrievalService() Constructor.

Method Summary

Modifier and Type	Method and Description
protected void	doStart()
protected void	doStop()
JMXMetricHolder	getCachedJMXMetric(String jmxUrl) Gets a cached JMX metric in the form of a JMXMetricHolder.
Map<String,String>	getCachedRESTMetric(String restUrl) Gets a cached REST metric in the form of a Map.
void	setThreadPoolExecutor(ThreadPoolExecutor threadPoolExecutor) Testing method for setting a synchronous ThreadPoolExecutor.
void	submitRequest(MetricsRetrievalService.MetricSourceType type, StreamProvider streamProvider, String url) Submit a Runnable for execution which retrieves metric data from the supplied endpoint.

Methods inherited from class com.google.common.util.concurrent.AbstractService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, failureCause, isRunning, notifyFailed, notifyStarted, notifyStopped, startAsync, state, stopAsync, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MetricsRetrievalService

public MetricsRetrievalService()

Constructor.

Method Detail

doStart

protected void doStart()

Specified by:

doStart in class com.google.common.util.concurrent.AbstractService

setThreadPoolExecutor

public void setThreadPoolExecutor(ThreadPoolExecutor threadPoolExecutor)

Testing method for setting a synchronous ThreadPoolExecutor.

Parameters:

threadPoolExecutor -

doStop

protected void doStop()

Specified by:

doStop in class com.google.common.util.concurrent.AbstractService

submitRequest

public void submitRequest(MetricsRetrievalService.MetricSourceType type,
                          StreamProvider streamProvider,
                          String url)

Submit a Runnable for execution which retrieves metric data from the supplied endpoint. This will run inside of an ExecutorService to retrieve metric data from a URL endpoint and parse the result into a cached value.

Once metric data is retrieved it is cached. Data in the cache can be retrieved via getCachedJMXMetric(String) or getCachedRESTMetric(String), depending on the type of metric requested.

Callers need not worry about invoking this multiple times for the same URL endpoint. A single endpoint will only be enqueued once regardless of how many times this method is called until it has been fully retrieved and parsed. If the last endpoint request was too recent, then this method will opt to not make another call until the TTL period expires.

Parameters:

type - the type of service hosting the metric (not null).

streamProvider - the StreamProvider to use to read from the remote endpoint.

url - the URL to read from

See Also:

getCachedJMXMetric(String)

getCachedJMXMetric

public JMXMetricHolder getCachedJMXMetric(String jmxUrl)

Gets a cached JMX metric in the form of a JMXMetricHolder. If there is no metric data cached for the given URL, then null is returned.

The onky way this cache is populated is by requesting the data to be loaded asynchronously via submitRequest(MetricSourceType, StreamProvider, String) with the MetricsRetrievalService.MetricSourceType.JMX type.

Parameters:

jmxUrl - the URL to retrieve cached data for (not null).

Returns:

the metric, or null if none.

getCachedRESTMetric

public Map<String,String> getCachedRESTMetric(String restUrl)

Gets a cached REST metric in the form of a Map. If there is no metric data cached for the given URL, then null is returned.

The only way this cache is populated is by requesting the data to be loaded asynchronously via submitRequest(MetricSourceType, StreamProvider, String) with the MetricsRetrievalService.MetricSourceType.REST type.

Parameters:

restUrl - the URL to retrieve cached data for (not null).

Returns:

the metric, or null if none.