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Ubic::Manual::OverviewUser Contributed Perl DocumentaUbic::Manual::Overview(3)

NAME
       Ubic::Manual::Overview -	General	ubic concepts and architecture

VERSION
       version 1.58

DESCRIPTION
   Services and	service	dir
       Ubic service is an object describing how	your service works.

       Service object must conform to the API of the Ubic::Service class, so
       it must implement "start", "stop" and "status" methods.	It can also
       provide other methods: which user should	be used	to run the service,
       how often the service should be checked by the watchdog,	etc.

       Service declarations are	stored in ubic service dir.  Service
       declaration is a	single file with perl code which returns service
       object when executed with "do".	If you use host-level installation,
       service dir is /etc/ubic/service. If you	prefer installation to home
       dir, service dir	is ~/ubic/service.

       Service file name can contain digits, letters underscores and dashes.
       Dot is not a valid symbol and all files with dots in their names	will
       be ignored.

   'ubic' script
       "ubic" script is	the main tool for manipulating your services.

       "ubic status" command, for example, will	show the list of all services
       declared	in service dir,	along with their statuses.  "ubic start" and
       "ubic stop" can be used to start	and stop all or	some services. Refer
       to ubic POD for more details.

   Service status
       Every service can report	its status via "status"	method.

       In the plane of perl API, statuses are instances	of Ubic::Result	class.
       Refer to	its POD	for gory details on various possible status values.

       Beside the real status, which can be calculated by calling "status"
       method, there is	also the cached	status,	stored on the disk in the
       special data dir.  This status is used in two ways.  First, users
       without appropriate rights to run actual	status check, can invoke "ubic
       status" command and see cached statuses.	 Second, watchdog process
       compares	cached status with current status to identify broken services
       and bring them back to life.

   Common service classes
       Since service descriptions are just a perl code,	you get	the full power
       of code reuse, and especially OOP-style code reuse, i.e.	inheritance.

       The most	important property of well-behaved service is that it would
       prevent you from	starting it twice, won't fail if you try to stop it
       twice, and will report correct statuses in all conditions.
       "Ubic::Service::Skeleton" helps you to do these things by asking	for
       current service status before start and stop operations.	It also	solves
       the common task of re-asking service status in a	loop with sleeps on
       start.

       "Ubic::Service::Common" class is	very similar to
       "Ubic::Service::Skeleton", but it allows	you to pass start/stop/status
       code via	callbacks instead of inheritance.

       Finally,	there is "Ubic::Service::SimpleDaemon",	which can turn any
       script or binary	into service. It uses "Ubic::Daemon" module for	all
       daemonization stuff.

       There are also some other modules on CPAN for more specific tasks:
       Ubic::Service::Plack, Ubic::Service::Memcached.

   Service tree
       Service dir can contain subfolders with service definitions inside of
       these subfolders. It allows you to group	your services together and
       make group operations on	them. For example, if you have
       "/etc/ubic/service/my/foo" and "/etc/ubic/service/my/bar" configs,
       "ubic stop -f my" will stop both	"my.foo" and "my.bar" services.

       What's even more	interesting is that subfolders with separate files in
       them is not the only way	to populate service tree. Read
       Ubic::Manual::Multiservices to learn more!

   Permissions and security
       Every service is	meant to be started by a specific user and group.
       Service can either provide user and group itself, or default user will
       be used.

       Default user is "root" on system-wide installations, and	the home
       folder owner on home dir	installations. You can change it in global
       "ubic.cfg" file.

       All service operations are performed using its user and group:
       start/stop operations, status checks, status file updates, watchdog
       checks. Ubic tries to change user to service user as soon as possible
       (but it still happens after service definition's	compilation, of
       course).	It means that service not only always started from correct
       user, even if you called	"ubic start foo" being root, for example, but
       also that service user is always	has enough grants to operate service
       too.

       This feature requires 1777 grants to ubic data dir (readable and
       writable	for everyone, but with sticky bit enabled). It should be
       secure, but if it worries you, you can try to change it to 1577
       (writable for specific group), and add all service users	to this	group.

       Note also that you can't	change user of existing	service	and expect
       your service to work. Refer to "Permission denied" question in
       Ubic::Manual::FAQ for more on this.

   Watchdog
       Default installation provides some services out of the box. The most
       important of them is ubic.watchdog.

       Watchdog	service	checks every service status periodically and restarts
       them if they are	broken or down.

AUTHOR
       Vyacheslav Matyukhin <mmcleric@yandex-team.ru>

COPYRIGHT AND LICENSE
       This software is	copyright (c) 2015 by Yandex LLC.

       This is free software; you can redistribute it and/or modify it under
       the same	terms as the Perl 5 programming	language system	itself.

perl v5.32.0			  2015-01-27	     Ubic::Manual::Overview(3)

NAME | VERSION | DESCRIPTION | AUTHOR | COPYRIGHT AND LICENSE

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