PhiAccrualFailureDetector
Implementation of 'The Phi Accrual Failure Detector' by Hayashibara et al. as defined in their paper: [http://www.jaist.ac.jp/~defago/files/pdf/IS_RR_2004_010.pdf]
The suspicion level of failure is given by a value called φ (phi). The basic idea of the φ failure detector is to express the value of φ on a scale that is dynamically adjusted to reflect current network conditions. A configurable threshold is used to decide if φ is considered to be a failure.
The value of φ is calculated as:
φ = -log10(1 - F(timeSinceLastHeartbeat)
where F is the cumulative distribution function of a normal distribution with mean and standard deviation estimated from historical heartbeat inter-arrival times.
- Value parameters:
- acceptableHeartbeatPause
Duration corresponding to number of potentially lost/delayed heartbeats that will be accepted before considering it to be an anomaly. This margin is important to be able to survive sudden, occasional, pauses in heartbeat arrivals, due to for example garbage collect or network drop.
- clock
The clock, returning current time in milliseconds, but can be faked for testing purposes. It is only used for measuring intervals (duration).
- firstHeartbeatEstimate
Bootstrap the stats with heartbeats that corresponds to to this duration, with a with rather high standard deviation (since environment is unknown in the beginning)
- maxSampleSize
Number of samples to use for calculation of mean and standard deviation of inter-arrival times.
- minStdDeviation
Minimum standard deviation to use for the normal distribution used when calculating phi. Too low standard deviation might result in too much sensitivity for sudden, but normal, deviations in heartbeat inter arrival times.
- threshold
A low threshold is prone to generate many wrong suspicions but ensures a quick detection in the event of a real crash. Conversely, a high threshold generates fewer mistakes but needs more time to detect actual crashes
- Source:
- PhiAccrualFailureDetector.scala
Value members
Constructors
Constructor without eventStream to support backwards compatibility
Constructor without eventStream to support backwards compatibility
Constructor that reads parameters from config.
Expecting config properties named threshold, max-sample-size,
min-std-deviation, acceptable-heartbeat-pause and
heartbeat-interval.
Constructor that reads parameters from config.
Expecting config properties named threshold, max-sample-size,
min-std-deviation, acceptable-heartbeat-pause and
heartbeat-interval.
Concrete methods
- Definition Classes
- Source:
- PhiAccrualFailureDetector.scala