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Intro - what is nepi-ng ?

As much as apssh comes with a standalone binary that sysadmins might find useful for their routine jobs, an alternative usage of apssh is to create SshJob objects in conjunction with an asyncio's Scheduler for orchestrating them.

Originally, the idea presented here addresses the needs of experimental research, where an experiment often boils down to running jobs like preparing a set of nodes, initializing them, running some bash script, collecting results, all of them having temporal relationships.

apssh and asynciojobs

asynciojobs

asynciojobs is a microscopic orchestration scheduler for asyncio-based jobs - see this link for details. This is the part that handles the temporal relationships.

apssh.SshJob

apssh ships with a few classes that allow you to write jobs in the asynciojobs sense, that will actually run on ssh:

  • SshNode : describe how to reach a node (possible through a gateway)
  • SshJob : to run one or several remote commands; each of these can be
    • Run : that is designed to run a command readily available on the target node
    • RunScript : when you have a local script file to run remotely, so there is a need to push it over there prior to running it
    • RunString : same idea, but you do not even have a local file, it's just a python string in memory; useful to embed your shell code inside a python code
    • Pull or Push for file transfers over SFTP

As the names may suggest:

  • an SshNode instance contains the details of the target node (hostname, username, gateway if relevant, etc...), and it can be thought of as an ssh connection;
  • SshJob, is suitable to run as asynciojobs's jobs, i.e. inside a scheduler;
  • an SshJob instance contains a list of the actual commands to run, that can be a mix of remote executions and file transfers.

example

You can see a very simple example of that idea implemented in 2 files