Unable to display candidate datastore content

[vxpyy9]

Hi,

I am currently using netconf-cli with a NETCONF server that supports NMDA. When making configuration changes, netconf-cli uses edit-data on the ds:candidate datastore. However, I am unable to display the content of the candidate datastore. Attempts to retrieve candidate data using ietf-netconf-nmda:get-data result in an InvalidNodeException and cause the CLI to crash.
I also tried using get-config with source candidate:

/> prepare ietf-netconf:get-config/
(prepare: /ietf-netconf:get-config) > set source/
candidate   running     startup 
(prepare: /ietf-netconf:get-config) > set source/candidate 
(prepare: /ietf-netconf:get-config) > exec
libyang[0]: Invalid empty value length 7. (schemadata path: /ietf-netconf:get-config/input/source/config-source/candidate/candidate)
Couldn't create a node with path '/ietf-netconf:get-config/source/candidate': LY_EVALID

Is it possible to somehow display the candidate datastore content so I can review pending configuration changes before committing them?

Thanks a lot.

[jktjkt]

Wow, nice :). This is a combination of several bugs:

• We're currently using this ill-fated concept of a "virtual datastore" where writes are targetting the candidate DS, and reads hit the operational DS. This looked like a good idea at the time we wrote that code, but there's a bunch of corner cases where it makes the life of the user very hard, so we'll change that behavior. This is the root cause, actually.
  -> Allow explicit running / candidate / operational DSes as a target for various operations #29
• People are "not supposed" to execute these low-level NETCONF RPCs directly via netconf-cli (but in this case you actually have to, because there's no way to execute the get command against the candidate DS). This should have been just an option to the CLI's get command, for example.
• The prepare vs. exec CLI commands -- once you've entered the prepare, then the exec command should not accept any argument. In this example, you're calling exec source/candidate, where the source/candidate is a leaf. The CLI parser should reject that, which is another bug in the CLI that we should fix :). I see that you've edited your bugreport in the meanwhile, and now you're using a correct syntax for setting these leafs.
  -> Extra parameters are accepted for exec in the prepare context #28
• Finally, the parsing of the NETCONF error reply is wrong, which has been fixed (twice). Once you upgrade libnetconf2-cpp, you'll get an error reply which tells you that a mandatory input parameter was missing. I see that you've changed that as well, good.
• Finally, the error message for Invalid empty value length 7. (schemadata path: /ietf-netconf:get-config/input/source/config-source/candidate/candidate) is a bit strange, we'll have to look into that.
  -> wrong empty handling in RPCs #30

[vxpyy9]

Thanks a lot for the detailed explanation!

Just to add - I’m seeing the same behavior with other empty leafs as well. For example:

/> prepare ietf-netconf:commit/
(prepare: /ietf-netconf:commit) > set confirmed 
(prepare: /ietf-netconf:commit) > exec 
libyang[0]: Invalid empty value length 7. (schemadata path: /ietf-netconf:commit/input/confirmed)
Couldn't create a node with path '/ietf-netconf:commit/confirmed': LY_EVALID