OverShell

Parallel Command Execution

The main goal of rugu is to simplify automated administrative tasks over ssh through a script-like interface. It is a common scenario that some agent, human or otherwise, must manage various server clusters; often times these clusters are heterogeneous in part or whole. For such scenarios, rugu provides the OverShell. An OverShell provides the same script-like interface used for a single server, but instead parallelizes execution over an arbitrary number of servers.

val base = Template(Host("host0"), UsernameAndPassword("xx", "xx"), knownHosts)
val hosts = (1 to 10).map("host%s".format(_))
val overshell = OverShell.stageHosts(hosts)(base)

overshell is now an OverShell instance for administering 10 servers in parallel. To execute a command we can use the same DSL as if we were executing on a single host. Here's how we print the host names as reported by executing the hostname command on each server:

overshell("hostname" :| identity).foreach(f => println(f.get))
Right(host1)
Right(host2)
Right(host3)
Right(host4)
Right(host5)
Right(host6)
Right(host7)
Right(host8)
Right(host9)
Right(host10)

Instead of returning a single result, OverShell#apply returns a sequence of Futures when all remote commands terminate. Sticking with the same example:

val futures = overshell("hostname" :| identity)

The type of futures is Seq[java.util.concurrent.Future[Either[Throwable,String]]]. OverShell uses ExecutorService#invokeAll to parallelize command execution, which means OverShell#apply blocks the calling thread until all remote commands terminate.

Parallel Uploads

OverShell also supports file uploads in parallel:

overshell.upload("local-fat.jar", "uploaded-fat.jar")

As for command execution, upload blocks the calling thread until all uploads complete. Just like commands, the actual uploads occur in parallel and only block the caller until all are finished.