Performance for system ssh and scp commands needs to be improved

[abhitoshj]

Is your feature request related to a problem? Please describe.
Whenever k2s system ssh and k2s system scp commands are executed, they take sometime more than 20-30 seconds to begin execution.
When many such commands have to executed in sequence, significate delays are observed.

Describe the solution you'd like
Improve performance of k2s system ssh and scp commands.

Describe alternatives you've considered
When many ssh commands have to be executed in sequence, I generally abstract all such commands in a bash script or a powershell script. This powershell script or bash script is copied onto the node using k2s system scp command and then executed with k2s system ssh commands, So the overall execution time is less than a minute.

Additional context
N.A.

[siprbaum]

Just wanting to at least present another option: start a connection to the node at the beginning and end it when everything is done. This would mean only the initial connection is slow, but the next connections will multiplex on the previous connection.

https://www.cyberciti.biz/faq/linux-unix-reuse-openssh-connection/

[achimkist]

ssh and scp are wrapped in a powershell script. The reason why it takes so long is the loading of the modules. Currently the "main" modules (infra. node, cluster modules) are loaded. When loading only the really needed ones the performance can be improved by 50%:

for ssh cmd:
current implementation: TotalMilliseconds : 6765.2381
loading only needed modules: TotalMilliseconds : 3598.6043

for scp cmd:
current implementation: TotalMilliseconds : 8059.982
loading only needed modules: TotalMilliseconds : 3614.6283

[jgriegershs]

Just wanting to at least present another option: start a connection to the node at the beginning and end it when everything is done. This would mean only the initial connection is slow, but the next connections will multiplex on the previous connection.

https://www.cyberciti.biz/faq/linux-unix-reuse-openssh-connection/

This can already be achieved with k2s system ssh [m|w] without adding a command. As result, the prompt to the node stays open until closed by the user or calling system. During that prompt multiple commands can be executed writing to the stdin stream.

[jgriegershs]

Ongoing discussion: #788 .

Related discussions: #787 and #789 .

[jgriegershs]

k2s node copy command is implemented as part of the performance issues mitigation.

This re-work will continue with #854, #855 and #856.