gossipmonger-peer

_Stability: 1 - Experimental_


GossipmongerPeer is a peer datastructure used by Gossipmonger, an implementation of the Scuttlebutt gossip protocol endpoint for real-time peer-to-peer peer-state distribution.

Usage

``javascript
var GossipmongerPeer = require('gossipmonger-peer');
// create local peer
var localPeer = new GossipmongerPeer(localId);

// on finding out about another peer
var otherPeer = new GossipmongerPeer(otherId);

// on making contact with otherPeer
otherPeer.markContact();

// on receiving a delta about otherPeer
otherPeer.updateFromDelta('otherFoo', 'otherBar', 17);

// test liveness criteria of otherPeer
if (otherPeer.phi() > MY_PHI_THRESHOLD) {
otherPeer.markDead();
}

// on changing some local peer value
localPeer.updateLocal('foo', 'bar');

// the dead rise! (made contact with otherPeer)
otherPeer.markLive();
`

Tests

npm test

Overview

Documentation

$3

Public API

* GossipmongerPeer.calculateIntervalsSum(intervals)
* [GossipmongerPeer.calculateIntervalsSumEfficiently(sum, newInterval, \[oldInterval\])](#gossipmongerpeercalculateintervalssumefficientlysum-newinterval-oldinterval)
* [new GossipmongerPeer(id, \[options\])](#new-gossipmongerpeerid-options)
* gossipmongerPeer.deltasAfterVersion(version)
* gossipmongerPeer.markContact(time)
* gossipmongerPeer.markDead()
* gossipmongerPeer.markLive()
* [gossipmongerPeer.phi(\[time\])](#gossipmongerpeerphitime)
* gossipmongerPeer.updateLocal(key, value)
* gossipmongerPeer.updateWithDelta(key, value, version)

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* intervals: _Array_ Intervals to calculate the sum of.
* Return: _Integer_ Calculated sum.

Iterates through intervals to calculate the sum.

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* sum: _Integer_ Current sum.
* newInterval: _Integer_ New interval being added to calculate the mean.
* oldInterval: _Integer_ _(Default: undefined)_ Old interval being removed
from being used in calculating the mean.
* Return: _Integer_ Calculated sum.

Instead of iterating through an array, simply adds newInterval to sum and substracts oldInterval if present.

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* id: _String_ Id of the peer.
* options: _Object_
* data: _Object_ _(Default: {})_ Peer data.
* intervals: _Array_ _(Default: [750])_ An array of the last
(up to MAX_INTERVALS) intervals between times when the peer has
been seen.
* intervalsMean: _Integer_ _(Default: undefined)_ Memoized intervals mean.
* lastTime: _Integer_ _(Default: undefined)_ The last time the peer has been seen (in milliseconds
since midnight Jan 1, 1970).
* live: _Boolean_ _(Default: true)_ Indicator whether or not the peer is
thought to be live.
* maxVersionSeen: _Integer_ _(Default: 0)_ Vector clock value indicating
the last version of the peer that has been observed.
* MAX_INTERVALS: _Integer_ _(Default: 100)_ The maximum number of
intervals to keep in intervals.
* sum: _Integer_ _(Default: undefined)_ Memoized sum of intervals to make
intervals mean calculation more efficient.
* transport: _Any_ Any data identifying this peer to the transport mechanism
that is required for correct transport operation.

Creates a new instance of GossipmongerPeer.

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* version: _Integer_ Vector clock version to construct deltas for.
* Return: _Array_ An array of deltas (ex delta: [key, value, version]).

Calculates deltas for this peer since version.

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* time: _Integer_ _(Default: new Date().getTime())_ The time this peer has
been seen (in milliseconds since midnight Jan 1, 1970).

Marks that contact with the peer occurred at time. This is used later in phi calculations.

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Sets live property to false.

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Sets live property to true.

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* time: _Integer_ _(Default: new Date().getTime())_ The time to use as
"now" in phi calculation (in milliseconds since midnight Jan 1, 1970).
* Return: _Number_ Calculated phi for this peer.

See The ϕ Accrual Failure Detector.

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* key: _String_ Key to update.
* value: _Any_ The value to update with.
* Return: _String_ If the key has been updated, the key is returned, otherwise
a null is returned instead.

Updates peer data and increments maxVersionSeen for the peer on which this is used. Intended for only manipulating data for the local peer.

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* key: _String_ The key for the value to update.
* value: _Any_ The value to update with.
* version: _Integer_ The vector clock version of this key value pair.
* Return: _String_ If the key has been updated, the key is returned, otherwise
a null is returned instead.

Updated peer data and sets maxVersionSeen to version if the version is greater than maxVersionSeen`. Intended for manipulating data for remote peers cached locally.

Sources

* The ϕ Accrual Failure Detector