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169 lines
7.2 KiB
Markdown
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| [Home](/trick) → [Developer Docs](Developer-Docs-Home) → Master-Slave |
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# Trick Master/Slave Synchronization Design
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Master/Slave synchronization is an optional class when running simulations.
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Master/Slave synchronization synchronizes a master simulation to one or more slave
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simulations. While synchronized, the master controls the overall simulation
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mode as well as the current simulation time for all simulations. The set of
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simulations may change mode if one of the simulations in the set freezes or exits
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unexpectedly.
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Master/Slave syncrhonization uses the Trick::MSConnect class for communications.
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The MSConnect class is an abstract base class that defines functions for
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connecting the simulations together and passing the simulation mode and
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simulation time between simulations. The Trick::MSSocket class derives from the
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Trick::MSConnect class, and uses sockets as the transport medium for master/slave communications.
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## Master
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The master simulation starts slave simulations during initialization. At the
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end of each software frame during Run mode and at the end of each freeze frame
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during Freeze mode the master reads the mode of all connected slave simulations.
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The master will determine the mode of the simulations for the next frame
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according to the slave modes and the master mode. The new mode and the
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current simulation time is sent to the slaves.
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Master/Slave synchronization is divided into code based on the mode of the
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simulation. The modes are Initialization, Run, Freeze, and Shutdown.
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Master/Slave functions are designed to be called from the S_define file.
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Listed below are the various modes of operation and the Master
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responsibilities within each.
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### Initialization -- Master
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During Initialization slave connections are allocated and defined. Default
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values to start each slave using ssh are set when a slave connection is
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allocated. At the mimimum a slave must define a remote machine, the path
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to the simulation executive, and a Trick::MSConnect class to use for
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communications with the slave. Users may also define the remote shell to use,
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a simulation executable name, a remote run directory, and additional user arguments
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to pass to the slave. The allocation and definition of the slave
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connections are typically done through Trick's input processor, but may also be
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done in default_data or initialization jobs.
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At the end of the scheduler initialization phase the master starts the slaves.
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For each slave the master creates a slave startup command and executes the
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slave startup command. This is how the slave startup command is created:
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1. If the MSConnect class is not defined, return an error.
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1. Begin the slave startup command with the slave remote shell.
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1. Add the remote display environment variable to the startup command if
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one was defined.
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1. Add a cd command to the slave simulation path directory to the slave starup
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command.
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1. Add the S_main executable name to the slave startup command.
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1. Add the Run Input File to the slave startup command.
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1. Add additional user arguments to the slave startup command.
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1. Execute the slave startup command.
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The master sends its software frame to each slave.
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### Run -- Master
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During Run mode the master reads the simulation mode of each slave. The
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master determines the new simulation mode and sends the new mode and the
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current simulation time to the slaves.
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1. For each slave
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1. Read the simulation command of the slave.
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1. If the master mode command is not ExitCmd take action if the slave
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returns the following:
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1. If the slave command was not readable, returned ErrorCmd, and:
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1. Terminate the sim if sync_error_terminate == true.
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1. Deactivate the slave if sync_error_terminate == false.
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1. If the slave command is ExitCmd:
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1. Terminate the sim if sync_error_terminate == true.
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1. Deactivate the slave if sync_error_terminate == false.
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1. If the slave command is FreezeCmd:
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1. Freeze the master sim
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After gathering the simulation command from all of the slaves, send the
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command to all of the slaves.
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1. For each slave
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1. Write the simulation time to the slave.
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1. Write the simulation mode command to the slave.
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### Freeze -- Master
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Upon entering freeze mode the master turns off sync_time_limit because while
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in freeze, master/slave communications may not be regular and periodic.
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At the end of each freeze frame call Trick::Master::end_of_frame() to perform the same
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synchronization as in run mode.
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When exiting freeze mode the master sets sync_time_limit back to the user
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set value ready for running again.
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### Shutdown -- Master
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The master tells the slaves that it is shutting down.
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1. For each slave
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1. Write the simulation time to the slave.
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1. Write the simulation mode command ExitCmd to the slave.
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## Slave
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At the end of each software frame during Run mode and at the end of each
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freeze frame during Freeze mode slave simulations send the master the current
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mode of the slave. The slaves wait for the new mode and simulation time from
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the master.
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### Initialization -- Slave
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The Trick::Slave class is enabled by calling the MSConnect::process_sim_args()
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routine. If the MSConnect::process_sim_args() finds command line arguments
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specifying this simulation is a slave, then the Trick::Slave is enabled.
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At the end of the scheduler initialization phase the slave connects to the
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master.
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1. Call Trick::MSConnect::connect() to connect the slave to the master.
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1. Search for a RealtimeSync class. If one exists, turn the object off.
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1. Search for a Master class. If one exists, turn the object off.
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1. Read and set the slave's software frame from the master.
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### Run -- Slave
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In Run mode the slave writes its next executive command to the master. The
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master will return the overall next simulation mode to the slave. The slave
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will also read the current simulation time from the master.
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1. Write the simulation command to the master.
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1. Read the simulation time from the master.
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1. if the simulation time read was not successful:
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1. Terminate the sim if sync_error_terminate == true.
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1. Disable master/slave communication and command the sim to freeze if sync_error_terminate == false.
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1. If the simulation time read was successful set the slave simulation
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time to the time of the master.
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1. Read the simulation command from the master.
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1. If the simulation command was not successful:
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1. Terminate the sim if sync_error_terminate == true.
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1. Disable master/slave communication and command the sim to freeze if sync_error_terminate == false.
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1. If the simulation command read was successful set the slave simulation
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command to the command of the master.
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### Freeze -- Slave
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Upon entering freeze mode the slave turns off sync_time_limit because while
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in freeze, master/slave communications may not be regular and periodic.
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At the end of each freeze frame call Trick::Slave::end_of_frame() to perform the same
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synchronization as in run mode.
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When exiting freeze mode the slave sets sync_time_limit back to the user
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set value ready for running again.
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### Shutdown -- Slave
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If a slave is shutting down, inform the master that it is exiting.
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[@anchor d_slave_shutdown_0 d_slave_shutdown_0]
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