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https://github.com/LatencyUtils/LatencyUtils

Utilities for latency measurement and reporting
https://github.com/LatencyUtils/LatencyUtils

Last synced: 29 days ago
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Utilities for latency measurement and reporting

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README 

          



LatencyUtils

============



A latency stats tracking package



The LatencyUtils package includes useful utilities for tracking latencies. Especially

in common in-process recording scenarios, which can exhibit significant coordinated

omission sensitivity without proper handling. LatencyStats instances are used to

track recorded latencies in the common use case the often follow this pattern:



```Java

 LatencyStats myOpStats = new LatencyStats();

 ...



 // During normal operation, record all operation latencies into a LatencyStats instance:



 long startTime = System.nanoTime();

 // Perform operation:

 doMyOperation(...);

 // Record operation latency:

 myOpStats.recordLatency(System.nanoTime() - startTime);

 ...



 // Later, report on stats collected:

 Histogram intervalHistogram = myOpStats.getIntervalHistogram();



 intervalHistogram.outputPercentileDistribution(System.out, 1000000.0);

```



The problem

-------------



Latency tracking of in-process operations usually consists simple time sampling around

a tracked operation. E.g. a database read operation for which latency statistics are

being developed may be surrounded by time measurement operation immediately before and

after the operation is performed, with the difference in time recorded in some aggregate

statistics gathering form (average, std. deviation, histogram,. etc.) which is later

used to report on the experienced latency behavior of the tracked operation.



The problem with this extremely common form of latency behavior tracking is that

whenever pauses occur in the system, latency statistics become significantly skewed

toward falsely-optimistic values. This occurs in two key ways:

- When a pause occurs during a tracked operation, a single long recorded latency

  will appear in the recorded values, with no long latencies associated with any

  pending requests that may be stalled by the pause.

- When a pause occurs outside of the tracked operation (and outside of the tracked

  time window) no long latency value would be recorded, even though any requested

  operation would be stalled by the pause.



The Solution

-------------



The LatencyStats class is designed for simple, drop-in use as a latency behavior

recording object in common in-process latency recording and tracking situations.

LatencyStats includes under-the-hood tracking and correction of pause effects,

compensating for coordinated omission. It does so by using pluggable pause detectors

and interval estimators that together with LatencyStats will transparently produce

corrected histogram values for the recorded latency behavior.