Lifebeat startup crashes with NullPointerException: hostName when WOHost isn't set #93

Summary

With -WOLifebeatEnabled YES but no -WOHost, application startup dies with

INFO ng.appserver.wointegration.NGLifebeatThread - Creating LifebeatThread: appName=Vacation, appPort=1299, hostName=null, wotaskdPort=1085, interval=PT30S
java.lang.NullPointerException: hostName

and the app never starts listening.

Where it comes from

• NGWOIntegrationPlugin.load() starts the lifebeat thread whenever WOLifebeatEnabled is set.
• NGLifebeatThreadRunner.start() passes properties.d().propWOHost() straight through; it's null when the property isn't given.
• NGLifebeatThread's constructor does Objects.requireNonNull( hostName, "hostName" ).

Reproduce

Run any ng app with wotaskd-style arguments, minus WOHost:

-WOPort 1299 -WOMonitorEnabled YES -WOLifebeatEnabled YES -WOLifebeatDestinationPort 1085 -WOLifebeatInterval 30 -WOApplicationName Vacation

Adding -WOHost localhost makes it start (and serve under the /cgi-bin/WebObjects/X.woa and /Apps/WebObjects/X.woa/1 prefixes) fine.

Thoughts

wotaskd normally passes -WOHost, so this mostly bites manual or scripted launches. But the failure is a bare NPE at startup that names a constructor parameter, not the property, so it takes a moment to connect it to WOHost. Options:

• default WOHost to the local host name, as WO does (as far as I remember, WOApplication.host() falls back to the machine's name);
• or fail with a message naming the missing property (WOLifebeatEnabled is set, but WOHost isn't).

Also worth a look while in there: the same _hostName is used both as the destination host for the wotaskd lifebeat URL and as the host the app reports for itself (sendMessage()), which is only right when wotaskd runs on the app's own host.

Related: #55 (proper wotaskd integration).