- This chapter begins the explanation of how to use Atropos code
by first developing a simple Magician application. This application performs
the simple task of generating active packets at a given rate. This application
is called LoadGenAppBasic and it will be kept as simple as possible. Atropos
will not be used until we build up to it a few chapters from now. The links
below point to specific sections of the LoadGenAppBasic code.
Key Concept
- Our first task is to create an active packet that generates
active packets. We will first focus on building how our active application
will behave. The code segment that generates and transmits an active packet
(which is found in LoadGenAppBasic) is shown here:
-
LoadPacket lp = new LoadPacket();
lp.SendForProcessing("AN-5");
|
-
- These two lines of code create an instance of an active packet
of class 'LoadPacket' and send it to active node 'AN-5'. We will want these
active packets to be created and transmitted at a given rate. Therefore, we
loop through the above code segment, generating and transmitting packets until
we reach the requested packets per second as shown in the code segment below:
-
while(Rate()
< PacketsPerSecond)
{
}
|
-
- The remaining code and class definitions are required to interface
with the Magician execution environment and to create the utility methods
needed to support the code in the loop above. There are three classes required
to implement the above code:
- LoadGenAppBasic: This class forms the
active packet that generates active packets and contains the loop shown above.
- LoadPacketAppBasic: This class
implements the active packets that are generated by LoadGenAppBasic.
- LoadAppBasicBase: This is a class
derived from the Magician active packet class and from which the above two
class are derived. This class handles the interface between this application
and Magician.
The explanation below provides detail on each section of the three classes.
LoadGenAppBasic
- package
- This is the usual Java package command. This AVNMP sample application
will be implemented within the specified package.
- imports
- The only required package that needs to be imported for this
example is the util package because the Date class is used to get the current
time.
- class
- The class for LoadGenAppBasic is defined here. Note that LoadGenAppBasic
is derived from LoadGenAppBasicBase
. The LoadBase class is a requirement of the Magician execution environment.
- numPkts
- This is the total number of packets transmitted. It is used
to determine the current number of packets that have been transmitted during
the last second.
- PacketsPerSecond
- This PacketsPerSecond method is used to determine the current
number of packets that have been transmitted during the last second.
- Date
- The Date class is required in order to get millisecond accuracy
in timing.
- LoadGenAppBasic
- Magician requires that a constructor exist. Here we have written
an empty constructor. However, in later chapters we will need to place code
within the constructor.
- milliSeconds
- This method returns the number of milliseconds since LoadGenAppBasic
began running.
- Seconds
- This method returns the number of seconds since LoadGenAppBasic
began running.
- Rate
- This method computes the rate of packet transmission LoadGenAppBasic
began running.
- exec
- This method overrides the Magician method within a Magician
packet. This is where the action occurs; the application, which is itself
an active packet, begins generating new packets -- LoadPacketAppBasic. Note that
the active LoadPacketAppBasic packet is sent to node AN-5. Any node name can
be used here as long as it is in the Magician configuration.
- sleep
- Sleep for a quarter of a second, allowing the active node to
process other packets.
LoadPacketAppBasic
- package
- This is the usual Java package command. This AVNMP sample application
will be implemented within the specified package.
- class
- The class for LoadGenAppBasic is defined here. Note that LoadGenAppBasic
is derived from LoadPacketAppBasic
. The LoadBase class is a requirement of the Magician execution environment.
- LoadPacketAppBasic
- Magician requires that a constructor exist. Here we use the
uptime of the LoadGenAppBasic application.
- exec
- This method overrides the Magician method within a Magician
packet. This is where the action occurs; in this case we can check whether
our packet is currently on the source or on the destination.
- Destination
check
- If we're on the destination node, then halt execution of the
packet.
LoadAppBasicBase
- package
- This is the usual Java package command. This AVNMP sample application
will be implemented within the specified package.
- imports
- The only required package that needs to be imported for this
example is the util package because the Date class is used to get the current
time.
- class
- The class for LoadAppBasicBase is defined here. The LoadBase
class is a requirement of the Magician execution environment.
- LoadGenAppBasicBase
- Magician requires that a constructor exist. Here we use the
uptime of the LoadGenAppBasic application.
- writeObject
- Serialize any external classes to be used within active packets.
Running the Active Application
After reading through this code and understanding what it does, you can compile
the code "as-is" using the included Makefile. Run in the Magician execution
environment by entering: send LoadGenAppBasic AH-1.
|
