Internals Documentation

The internals documentation covers the design and functionality of ISM and related projects. The target audience is developers and operators.

Developers should have familiarity with:

• Isabelle: server and related components
• Golang: Basic Language knowledge around concurrent and network programming
• Linux: Basic knowledge around the network stack, cgroups, namespaces (user, network) and security
• systemd: Basic knowledge around services and cgroups integration

While operators only need familiarity with Linux and Isabelle.

Interesting Material

Below is a loose collection of interesting material for reading up on relevant topics. The documentation doesn't expect you to know all of this.

• LWN: Linux news and articles
  • Namespaces, everything from the Kernel/Namespaces index but in particular:
  • Network namespaces
  • Namespaces in operation, part 7: Network namespaces
• systemd: system and service manager, backbone of ISM
  • systemd.unit / systemd.slice / systemd.service / systemd.resource-control
  • systemd-run
• Linux Kernel: For FS and supervision layer
  • Shared Subtrees
  • Overlay Filesystems
  • strace, very useful for debugging mount issues
• Golang
  • Profiling Go Programs
  • Arrays, slices (and strings): The mechanics of 'append'
  • Go Wiki: Compiler And Runtime Optimizations
  • Effective Go: Concurrency
  • Go Concurrency Patterns: Context / Contexts and structs
  • Dmitry Vyukov — Go scheduler: Implementing language with lightweight concurrency (Video)
• Incus: Current/ New executor

Relevant courses

If you're a student at TUB you will benefit from having taken the courses:

• TKN Rechnernetze und verteilte Systeme
• Algorithmen und Datenstrukturen
• Systemprogrammierung

They will aid with network and concurrent programming.

Appendix

The nomenclature can be a bit confusing given the overuse of "server" and "instance". Below a small definition of used components and their names.

• server instance: A running systemd unit, managed by ISM, containing an isabelle server
• server handle: The internal representation of a server instance in ISM
• server pool: A pool of running server instances manged by the Agent and used by the Gateway
• Gateway: An ISM component facilitating the communication between clients and server instances
• Agent: An ISM component facilitating the monitoring of server instances and server pool management.
• Monitoring clients: ISM managed isalink.IsaClients used for monitoring by the agent