History

How to configure or address all resources within a defined group, and use simple substitutions¶

1. Prerequisites¶

Make sure that you understand how OMF works from a user's point of view.
Make sure that you have completed and understood the basic "Hello World" tutorial.

2. Goal¶

This tutorial shows you:
- how to configure or address all the resources in one specific group or all the groups defined in your experiment
- how to use the basic substitution feature of OMF

3. Scenario¶

Here we are using the same simple scenario as in the basic "Hello World" tutorial.

We will modify this example, to allow us to:
- configure the 1st wireless interface of all the resources in all the groups in a unique block of command
- address all the resource in a specific group with a given request, e.g. start all applications.

4. The New "Hello World" Experiment Description¶

The Experiment Description (ED) describing this simple experiment is (download it here: using-groups.rb):

 1 defGroup('Sender', "omf.nicta.node2") do |node|
 2   node.addApplication("test:app:otg2") do |app|
 3     app.setProperty('udp:local_host', '%net.w0.ip%')
 4     app.setProperty('udp:dst_host', '192.168.255.255')
 5     app.setProperty('udp:broadcast', 1)
 6     app.setProperty('udp:dst_port', 3000)
 7     app.measure('udp_out', :samples => 1)
 8   end
 9 end
10 
11 defGroup('Receiver', "omf.nicta.node3") do |node|
12   node.addApplication("test:app:otr2") do |app|
13     app.setProperty('udp:local_host', '192.168.255.255')
14     app.setProperty('udp:local_port', 3000)
15     app.measure('udp_in', :samples => 1)
16   end
17 end
18 
19 allGroups.net.w0 do |interface|
20   interface.mode = "adhoc" 
21   interface.type = 'g'
22   interface.channel = "6" 
23   interface.essid = "helloworld" 
24   interface.ip = "192.168.0.%index%" 
25 end
26 
27 onEvent(:ALL_UP_AND_INSTALLED) do |event|
28   wait 10
29   group("Receiver").startApplications
30   wait 5
31   group("Sender").startApplications
32   wait 30
33   group("Sender").stopApplications
34   wait 5
35   group("Receiver").stopApplications
36   Experiment.done
37 end

The Experiment Description (ED) describing this simple experiment is (download it here: using-groups.rb):

Line 19-25: we use the allGroups command to configure some parameters on all the nodes in all the groups
- Line 19: allGroups is followed by a Resource Path net.w0, which specify a network interface resource (net), and more specifically the 1st wireless one (w0). In the following block (line 20-24), this net.w0 network resource is known as interface.
- Line 20: configure the mode parameter of the interface to the value "adhoc". This would have been equivalent to the net.w0.mode = "adhoc" line used in the Hello World tutorial
- Line 24: uses OMF's substitution feature to configure the ip parameter of the interface:
  - Here the value is set to "192.168.0%index%"
  - OMF assign a unique integer value to each resource, i.e. an index
  - When OMF sees %index%, for each node in all the groups it will substitute the %index% string by the node's index value
  - For example, on a resource which as the index 3, the value "192.168.0.%index%" will be replaced by "192.168.0.3"
  - The following substitution strings are valid in OMF 5.3:
    - %index% - replaced by the resource's unique index
    - %hostname% - replaced by the resource's hostname, if any
    - %net.w0.ip% - replaced by the value of the resource's parameter net.w0.ip
    - %net.XX.YYY% - replaced by the value of the resource's parameter net.XX.YYY
  - Note: This substitution is done locally at the Resource Controller running on the resource.

Line 3: we configure one parameter of the application OTG2 using the substitution net.w0.ip
- On each resource in the group Sender, the application OTG2 will have its udp:local_host parameter set to the IP address of the 1sst wireless interface

Line 29, 31, 33, 35: we use the group command to address a specific group
- Line 29: we send the request startApplications only to the resources which are in the specific group "Receiver". This is different from what we did in the Hello World tutorial.
- We do the same for different request with different groups in the remaining lines

Another example of the these features is:
- group('Sender').net.w0.channel = 11
- which assign the value 11 to the channel parameter of the 1st wireless interface of all the resources in the group Sender

Finally... Please refer to the basic "Hello World" tutorial if you do not understand the remaining lines of the above ED.

5. Running the experiment & using the results¶

Running this experiment and accessing/using its results are exactly similar as running the "Hello World" tutorial and accessing/using its results. Thus, please refer to the "Hello World" tutorial.

6. What is Next?¶

Now that you know how to configure/address groups of resources, you may want to read the following basic OMF tutorials. Each one of them is introducing an OMF feature, using the simple "Hello World" experiment as a base. You do not need to follow them in the order suggested below.