Cache connections

[pmeinhardt]

As outlined in #3, it may be useful to cache connections for SSHKit.Contexts so subsequent commands do not have to set up a new one each time.

Open questions/things to do:

• How do we cache connections?
  • should be a KV-store erlang process
  • probably store connections by {hostname, port, username} as the key?
  • commands always go to this process to fetch a connection
    • if a connection with the same key doesn't exist yet, create, cache and return it
    • else: return the cached connection unless it timed-out
  • so it's more of a "connection provider" than just a "cache"
• How do we reuse the cached connections?
  • do we pass them in to the SSHKit.run and .upload functions?
  • do these methods access the (global) cache process?

Thoughts:

• use GenServer for the connection provider
• could be set as part of the context, but have a default value so you do not need to explicitly pass it when just using the DSL

context = SSHKit.context(hosts, provider: SSHKit.ConnectionProvider.new)

# in SSHKit

  def context(hosts, options \\ [provider: SSHit.ConnectionProvider.default])
    …
  end

  def run(context, command) do
    # fetch connections from the context's connection provider
    # execute
  end

[pmeinhardt]

Closing this. I think that making the connection explicit to enable re-use is a better next goal (see first draft in #138). Once that's achieved, connection caching could be implemented on top/outside of SSHKit.