Package org.apache.accumulo.test.metrics

Class MetricsFileTailer

java.lang.Object

org.apache.accumulo.test.metrics.MetricsFileTailer

All Implemented Interfaces:

AutoCloseable

public class MetricsFileTailer
extends Object
implements AutoCloseable

This class allows testing of the publishing to the hadoop metrics system by processing a file for metric records (written as a line.) The file should be configured using the hadoop metrics properties as a file based sink with the prefix that is provided on instantiation of the instance. This class will simulate tail-ing a file and is intended to be run in a separate thread. When the underlying file has data written, the value returned by getLastUpdate will change, and the last line can be retrieved with getLast().

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MetricsFileTailer.LineUpdate

Constructor Summary

Constructors

Constructor	Description
MetricsFileTailer(String metricsPrefix)	Create an instance that will tail a metrics file.

Method Summary

Modifier and Type	Method	Description
void	close()
String	getLast()	Get the last line seen in the file.
long	getLastUpdate()	Creates a marker value that increases each time a new line is detected.
Map<String,String>	parseLine(String prefix)	The hadoop metrics file sink published records as a line with comma separated key=value pairs.
void	startDaemonThread()
MetricsFileTailer.LineUpdate	waitForUpdate(long prevUpdate, int maxAttempts, long delay)

Methods inherited from class java.lang.Object

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

Constructor Detail

MetricsFileTailer

public MetricsFileTailer(String metricsPrefix)

Create an instance that will tail a metrics file. The filename / path is determined by the hadoop-metrics-accumulo.properties sink configuration for the metrics prefix that is provided.

Parameters:

metricsPrefix - the prefix in the metrics configuration.

Method Detail

getLastUpdate

public long getLastUpdate()

Creates a marker value that increases each time a new line is detected. Clients can use this to determine if a call to getLast() will return a new value. However, this value is NOT a timestamp and should not be interpreted as such. Furthermore, it does not indicate that the metrics being reported have changed, only that a new metrics poll took place and was written to the file. So, if clients need to observe new metrics from a new event, they need to parse the line themselves to look for changed metrics values.

Returns:

a marker value set when a new line is available.

getLast

public String getLast()

Get the last line seen in the file.

Returns:

the last line from the file.

parseLine

public Map<String,String> parseLine(String prefix)

The hadoop metrics file sink published records as a line with comma separated key=value pairs. This method parses the line and extracts the key, value pair from metrics that start with an optional prefix and returns them in a sort map. If the prefix is null or empty, all keys are accepted.

Parameters:

prefix - optional filter - include metrics that start with provided value..

Returns:

a map of the metrics that start with AccGc

startDaemonThread

public void startDaemonThread()

close

public void close()

Specified by:

close in interface AutoCloseable

waitForUpdate

public MetricsFileTailer.LineUpdate waitForUpdate(long prevUpdate,
                                                  int maxAttempts,
                                                  long delay)