Symphony processes

There are multiple Symphony processes running on each host in the cluster. The type and number of processes running depends on whether the host is a management host or a compute host.

Management host processes

Symphony management hosts run various processes, depending on their role in the cluster.

On the master host

master lim

The master lim starts vemkd and pem on the master host. There is one master lim per cluster.

vemkd
The vemkd (EGO kernel) does the following:
  • Starts the service controller egosc

  • Maintains security policies, allowing only authorized access

  • Maintains resource allocation policies, distributing resources accordingly

  • Serves as an information center where clients can query information about the cluster

There is one vemkd per cluster, and it runs on the master host.

pem

The pem (process execution monitor) monitors vemkd, and notifies the master lim if vemkd fails.

egosc

The egosc (EGO service controller) is the first service that runs on top of the EGO kernel. It functions as a bootstrap mechanism for starting the other services in the cluster. It also monitors and recovers the other services. It is somewhat analogous to init on UNIX systems or Service Control Manager on Windows systems. After the kernel boots, it reads a configuration file to retrieve the list of services to be started. There is one egosc per cluster, and it runs on the master host.

sd

The sd (session director) acts as a liaison between the client application and the session manager. There is one session director process per cluster, and it runs on the master or a management host.

This process could also run on other management hosts.

rs

The rs (repository service) provides a deployment mechanism for service packages to the compute hosts in the cluster. There is one repository service per cluster, and it runs on the master or a management host.

This process could also run on other management hosts.

On other management hosts

lim

The lim (load information manager) monitors the load on the management host, and starts pem.

pem

The pem (process execution manager) starts Symphony processes on the host.

ssm

The ssm (session manager) is the primary workload scheduler for an application. There is one session manager per application.

wsm

The wsm (web interface service) runs the Platform Management Console.

plc

The plc (PERF loader controller) loads data into the reporting database.

purger

The purger (PERF data purger) purges reporting database records.

On the master candidate hosts

lim

The lim (load information manager) monitors the load on the master candidate host. lim also monitors the status of the master lim. If the master host fails, lim also elects a new master host.

pem

The pem (process execution manager) starts Symphony processes on the host.

Compute host processes

lim

The lim (load information manager) monitors the load on a compute host, and passes the load information to the master lim on the master host.

The lim does the following for the host on which it runs:
  • Starts pem on that host

  • Provides system configuration information to the master lim

  • Monitors load and provides load information statistics to vemkd and users

pem

The pem (process execution manager) monitors the lim process.

sim

The sim (service instance manager) is started on the compute host when workload is to be submitted to the host if the application is preconfigured. The sim then starts the service instance running. There is one service instance manager per service instance.