13 The Service Controller
The HELIOS Service Controller "srvsrv" is a feature which has been added to the software in the 4th generation release. It starts, stops and monitors all HELIOS server processes, like "afpsrv", "pcshare", "lpd", etc. (the figure on the next page shows HELIOS' three levels of service reliability).
This feature prevents a possible server process failure for a single client from bringing down all the served clients on the network. By having a separate process for each client computer, each user is effectively insulated from other users. The more users on the network, the more important this feature.
Automatic process restart on failure
The HELIOS Service Controller monitors all processes which have been started on the server. In case a process should fail, the HELIOS Service Controller restarts this process after a short time.
- Automatic service restart 10 seconds after failure
- Automatic disable after 10 failures; each failure within a minute
- Automatic starting order of the services, e.g.:
- afpsrv first
- opisrv second
- -
- Automatic stopping order
- Complete error logging into "syslog" file
- Third party applications can integrate their services into the HELIOS Service Controller (via preferences; see also 13.2 "Integrating additional services").
"srvutil" is a server utility which lets you manipulate single HELIOS services, e.g. starting, stopping, reconfiguring, or just status monitoring. Actually, it passes requests to the "srvsrv " daemon which is described above.
The following options can be used with the "srvutil " command, where
[-f] stands for
forced,
[-r] for
recursive,
[-g] for
grace period and
[-m] for
message.
srvutil start all (root only)
srvutil start [-r] [-f] service... (root only)
srvutil stop all (root only)
srvutil stop [-r] [-f] service... (root only)
srvutil stop [-g] [-m] service... (root only)
srvutil reconf all (root only)
srvutil reconf service... (root only)
srvutil status (all users)
Starts service though depending services might not yet run.
Stops service though depending services might still run.
Starts service and all other depending services.
Stops service and all other depending services.
Stops service in a specified time period, optionally with a shutdown message
[-m].
Note: This option has only effect on "afpsrv" and "pcshare" services. Other services such as "lpd", "admsrv", etc. will ignore it.
bin/srvutil stop -f pcshare
This command stops the PCShare service ("pcshare") though "opisrv", which depends on "pcshare", is still running.
Causes a master process to reread its configuration file or preferences.
Shows the status of all installed (HELIOS) services.
13.2 Integrating additional services
The HELIOS Service Controller can also be used to start and stop additional server processes.
If you want to integrate additional services into the HELIOS software, which are administered by the HELIOS Service Controller, do the following:
Generate a text file containing the preference(s) for a new service and save it under a suitable name, e.g. "myservice.prefs".
A simple example for a service preference file is: "HELIOSDIR/etc/prefs/lpd.prefs".
[][Services][myservice][ExecPath]
[][Services][myservice][OptDependsOn]
The above example defines a service executable
"sbin/myservice" that must be started after "atalkd", "desksrv", "afpsrv", and "pcshare".
Install the preferences for the new service via:
prefrestore myservice.prefs
The new service is started with the next "start-helios" command.
