uri-monitor v0.5.0-0

:toc: macro :toc-title: :toclevels: 9

URI Monitor

image:https://circleci.com/gh/jasonkuhrt/uri-monitor.svg?style=svg["Circle CI", link="https://circleci.com/gh/jasonkuhrt/uri-monitor"]

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Installation

npm install --save uri-monitor

Examples

Basis for following examples:

import Monitor from 'uri-monitor'

const monitor = Monitor.create('https://foo.io', 1500)

Monitoring outages:

const serviceChanges = monitor.filter(({ type }) => type === 'change')

serviceChanges
.filter({ data: { isResponsive }} => !isResponsive)
.observe(({ data: { result }}) => console.warn('Service Down!', result))

serviceChanges
.filter({ data: { isResponsive }} => isResponsive)
.observe(() => console.warn('Service Up!'))

Monitoring outages via <<convenience-streams-on-stream, Stream sugar>>:

monitor
.downs
.observe(() => console.warn('Service Down!'))

serviceChanges
.ups
.observe(() => console.warn('Service Up!'))

API

.create

create :: String, Maybe Integer -> Stream MonitorEvent
--        uri     interval

• uri The URI that periodic GET requests will be made to.

• interval Optional, defaults to 1000. The milliseconds between each request. Note this is not the time between a response and the next request because requests are evenly staggered. For example:

+

--- = Time    Q = Request    R = Response

Q1----R1-Q2-R2----Q3--R3---Q4--
^        ^        ^        ^    <== Evenly staggered

+ A response cannot temporally leak into the next request because each request is configured to timeout within the interval.

Definition of request failure

The following will cause the result of a request to be considered a failure:

• Request is not responded to within interval
• Response HTTP Status Code is >= 400.
• Any general HTTP Error (e.g. a client-side CORS error)

In all of these cases data.isResponsive will be false and data.result will be either a <<requesterror, RequestError>> or <<networkerror, NetworkError>>.

Convenience streams on Stream

The <<stream,Stream>> returned by <<create, create>> is monkey patched with filtered variants for common patterns. They are:

.pongs

pongs :: Stream CheckedEvent

<<checkedevent, CheckedEvents>> where data.isResponsive is true.

.drops

drops :: Stream CheckedEvent

<<checkedevent, CheckedEvents>> where data.isResponsive is false.

.ups

ups :: Stream ChangedEvent

<<changedevent, ChangedEvents>> where data.isResponsive is true.

.downs

ups :: Stream ChangedEvent

<<changedevent, ChangedEvents>> where data.isResponsive is false.

Types

Stream

An instance of link:https://github.com/cujojs/most/blob/master/docs/api.md[most].

MonitorEvent

Base interface that all emitted events implement. If isResponsive is false then result is either a <<requesterror, RequestError>> or <<networkerror, NetworkError>> otherwise result is a <<response, Response>>.

type : String
data :
  isResponsive: Bool
  result: CheckResult

CheckedEvent

Emitted every time a result of a request is available.

type: "checked"
data:
  isResponsive: Bool
  result: CheckResult

ChangedEvent

Emitted every time a result of a request has a different isResponsive value than the previous result.

type: "changed"
data:
  isResponsive: Bool
  result: CheckResult

CheckResult

RequestError | NetworkError | Response

Response

A link:https://visionmedia.github.io/superagent/#response-properties[Superagent Response].

RequestError

message: String
status: Integer
body: Object
res: Response

NetworkError

message: String
originalError: Object