Changed strategy for probe scheduling to ensure there is only one pen…

…ding probe at a time to avoid resource exhaustion in edge cases, e.g. if there is no response from peer on HTTP connect. Minor changes.

README.md

@@ -2,9 +2,7 @@
 
 [![npm version](https://badge.fury.io/js/pimatic-probe.svg)](http://badge.fury.io/js/pimatic-probe)
 
-A pimatic plugin to probe HTTP(S), TCP and UDP services.
-
-Note: UDP is currently not supported and will be added at a later stage!
+A pimatic plugin to probe HTTP(S) and TCP services.
 
 ## Configuration
 
@@ -92,7 +90,7 @@ By default, HttpProbe does not verify the server certificate if connected to a H
  enabled by setting the `verifyPeerCert` property to `true`. In this case, HttpProbe will fail (`absent` state) if the 
  server certificate cannot be verified.
 
- {
+    {
         "id": "probe4",
         "class": "HttpProbe",
         "name": "Router Web Page with Basic Auth",
@@ -233,4 +231,8 @@ If you wish to hide the sparkline (the mini-graph) of `connectTime` attribute di
     * Dependency updates
 * 20150918, V0.1.1
     * Dependency updates
-    * Minor changes
+    * Minor changes
+* 20151116, V0.2.0
+    * Changed strategy for probe scheduling to ensure there is only one pending probe at a time to avoid 
+      resource exhaustion in edge cases, e.g. if there is no response from peer on HTTP connect.
+    * Minor changes

package.json

@@ -1,17 +1,17 @@
 {
   "name": "pimatic-probe",
-  "description": "A pimatic plugin to probe HTTP(S), TCP and UDP services",
+  "description": "A pimatic plugin to probe HTTP(S), TCP services",
   "author": {
     "name": "Marcus Wittig",
     "url": "https://github.com/mwittig/pimatic-probe"
   },
   "main": "probe",
   "files": [
     "probe.coffee",
-    "README.md",
     "probe-config-schema.coffee",
     "device-config-schema.coffee",
-    "LICENSE"
+    "LICENSE",
+    "README.md"
   ],
   "version": "0.1.1",
   "homepage": "https://github.com/mwittig/pimatic-probe",

probe.coffee

@@ -77,25 +77,23 @@ module.exports = (env) ->
       super()
 
       if not @deviceConfigurationError
-        @_scheduleUpdate()
+        # perform an update now
+        @_requestUpdate()
 
 
     # poll device according to interval
     _scheduleUpdate: () ->
-      if typeof @intervalObject isnt 'undefined'
-        clearInterval(=>
-          @intervalObject
-        )
+      if @timeoutObject?
+        clearTimeout @timeoutObject
 
-      # keep updating
       if @interval > 0
-        @intervalObject = setInterval(=>
+        # keep updating
+        @timeoutObject = setTimeout( =>
+          @timeoutObject = null
           @_requestUpdate()
         , @interval
         )
 
-      # perform an update now
-      @_requestUpdate()
 
     _requestUpdate: ->
       @_ping().then(=>
@@ -106,6 +104,8 @@ module.exports = (env) ->
         env.logger.error newError if @_lastError isnt newError or @debug
         @_lastError = newError
         @_setPresence (no)
+      ).finally( =>
+        @_scheduleUpdate()
       )
 
     _ping: ->
@@ -159,7 +159,7 @@ module.exports = (env) ->
       @_presence = lastState?.presence?.value or false
       @_port = config.port
       @interval = Math.max 1000 * config.interval, 10000
-      @_timeout = Math.min @interval, config.timeout * 1000
+      @_connectTimeout = Math.min @interval, config.timeout * 1000
 
       if config.enableConnectTime
         @addAttribute('connectTime', {
@@ -177,26 +177,24 @@ module.exports = (env) ->
           env.logger.error "Probe for device id=#{@id}. host=#{config.host}: Name Lookup failed: " + error
         else
           @_host = address
-          @_scheduleUpdate()
+          # perform an update now
+          @_requestUpdate()
       )
 
+
     # poll device according to interval
     _scheduleUpdate: () ->
-      if typeof @intervalObject isnt 'undefined'
-        clearInterval(=>
-          @intervalObject
-        )
+      if @timeoutObject?
+        clearTimeout @timeoutObject
 
-      # keep updating
       if @interval > 0
-        @intervalObject = setInterval(=>
+        # keep updating
+        @timeoutObject = setTimeout( =>
+          @timeoutObject = null
           @_requestUpdate()
         , @interval
         )
 
-      # perform an update now
-      @_requestUpdate()
-
     _requestUpdate: ->
       @_connect().then(=>
         @_setPresence (yes)
@@ -205,13 +203,15 @@ module.exports = (env) ->
         env.logger.error newError if @_lastError isnt newError or @debug
         @_lastError = newError
         @_setPresence (no)
+      ).finally( =>
+        @_scheduleUpdate()
       )
 
     _connect: ->
       return new Promise((resolve, reject) =>
         timeStart = process.hrtime()
         client = new net.Socket
-        client.setTimeout(@_timeout, =>
+        client.setTimeout(@_connectTimeout, =>
           client.destroy()
           reject(new Error "TCP connect attempt timed out")
         )