== Resource Resolution

- A global configuration <<resources_conf,resources.conf>> defines which hardware is plugged to the
  {app-name} setup, be it the main unit or any slave unit. This list becomes the
  'resource pool'.
- Each suite contains a number of test scripts. The amount of resources a test
  may use is defined by the test suite's <<suite_conf,suite.conf>>.
- Which specific modems, BTS models, NITB IP addresses etc. are made available
  to a test run is typically determined by <<suite_conf,suite.conf>> and a combination of <<scenario_conf,scenario
  configurations>> -- or picked automatically if not.

.Example of how to select resources and configurations: scenarios may pick specific resources (here BTS and ARFCN), remaining requirements are picked as available (here two modems and a NITB interface)
[graphviz]
----
digraph G {
	rankdir=TB;

	suite_scenarios [label="Suite+Scenarios selection\nsms:sysmo+band1800+mod-bts0-chanallocdescend"]

	subgraph {
		rank=same;
		suite
		scenarios
                defaults_conf [label="defaults.conf:\nbsc: net: encryption: a5_0"]
	}

	subgraph cluster_scenarios {
		label = "Scenarios";
		u_sysmoBTS [label="Scenario: sysmo\nresources: bts: type: osmo-bts-sysmo"]
		u_trx [label="Scenario: trx\nresources: bts: type: osmo-bts-trx"]
		u_arfcn [label="Scenario: band1800\nresources: arfcn: band: GSM-1800"]
		u_chanallocdesc [label="Scenario: band1800\nmodifiers: bts: channel_allocator: descending"]
	}

	subgraph cluster_suite {
		label = "Suite: sms";
		requires [label="Requirements (suite.conf):\nmodem: times: 2\nbts\nip_address\narfcn"]
		subgraph cluster_tests {
			label = "Test mo_mt_sms.py";
			obj_nitb [label="object NITB\n(process using 10.42.42.2)"]
			bts0 [label="object bts[0]"]
			modem0 [label="object modem[0]"]
			modem1 [label="object modem[1]"]
		}
	}

	subgraph cluster_resources {
		label = "Available Resources (not already allocated by other Osmo-GSM-Tester instance)";
		rankdir=TB;
			nitb_addrA [label="NITB interface addr\n10.42.42.1"]
			nitb_addrA [label="NITB interface addr\n10.42.42.2"]
			ModemA
			ModemB
			ModemC
			sysmoBTS [label="osmo-bts-sysmo"]
			osmo_bts_trx [label="osmo-bts-trx"]
			arfcnA [label="arfcn: 512\nband: GSM-1800"]
			arfcnB [label="arfcn: 540\nband: GSM-1900"]

			arfcnA->arfcnB [style=invis]
			nitb_addrA->nitb_addrB [style=invis]
			ModemA -> ModemB -> ModemC [style=invis]
			sysmoBTS -> osmo_bts_trx [style=invis]
	}

	suite_scenarios -> {suite scenarios}
	scenarios -> { u_arfcn u_sysmoBTS u_chanallocdesc }

	suite -> requires
	requires -> ModemA
	requires -> ModemB
	requires -> sysmoBTS
	requires -> arfcnA
	requires -> nitb_addrA

	{ u_sysmoBTS u_arfcn } -> requires [label="influences\nresource\nselection"]
	u_chanallocdesc -> bts0 [label="influences\nbts[0]\nbehavior"]
        defaults_conf -> obj_nitb [label="provides default values"]
}
----

=== Resource Reservation for Concurrent Trials

While a test suite runs, the used resources are noted in a global state
directory in a reserved-resources file. This way, any number of trials may be
run consecutively without resource conflicts. Any test trial will only use
resources that are currently not reserved by any other test suite. The
reservation state is human readable.

The global state directory is protected by a file lock to allow access by
separate processes.

Also, the binaries from a trial are never installed system-wide, but are run
with a specific 'LD_LIBRARY_PATH' pointing at the <<trials,trial's inst>>, so that
several trials can run consecutively without conflicting binary versions. For
some specific binaries which require extra permissions (such as osmo-bts-octphy
requiring 'CAP_NET_RAW'), 'patchelf' program is used to modify the binary
'RPATH' field instead because the OS dynamic linker skips 'LD_LIBRARY_PATH' for
binaries with special permissions.

Once a test suite run is complete, all its reserved resources are torn down (if
the test scripts have not done so already), and the reservations are released
automatically.

If required resources are unavailable, the test trial fails. For consecutive
test trials, a test run needs to either wait for resources to become available,
or test suites need to be scheduled to make sense. (*<- TODO*)

=== Understanding config parsing process

include::{srcdir}/chapters/config_mangling.adoc[]