Add type checking of fields in Layer specification to avoid list vs str issues

When defining dependent layer (based on Layer specification) I’ve noticed that I cannot use layer names longer than 1 character. If I change layer definition to p, everything works.

        return {                                                                
            "summary": "opensearch layer",                                      
            "description": "pebble config layer for opensearchproject/opensearch",
            "services": {                                                       
                "procps": {                                                     
                    "override": "merge",                                        
                    "command": "yum install -y procps",                         
                    "startup": "enabled",                                       
                    "summary": "procps",                                        
                },                                                              
                "opensearch": {                                                 
                    "requires": "procps",                                       
                    "override": "merge",                                        
                    "environment": environment,                                 
                    "summary": "opensearch",                                    
                    "command": cmd,                                             
                    "startup": "disabled",                                      
                }                                                               
            }                                                                   
        }                                                                       

unit-opensearch-k8s-0: 16:12:32 ERROR juju.worker.uniter.operation hook "opensearch-pebble-ready" (via hook dispatching script: dispatch) failed: exit status 1
unit-opensearch-k8s-0: 16:12:32 ERROR juju.worker.uniter pebble poll failed for container "opensearch": hook failed
unit-opensearch-k8s-0: 16:12:37 ERROR unit.opensearch-k8s/0.juju-log Uncaught exception while in charm code:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/pebble.py", line 729, in _request_raw
    response = self.opener.open(request, timeout=self.timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 531, in open
    response = meth(req, response)
  File "/usr/lib/python3.8/urllib/request.py", line 640, in http_response
    response = self.parent.error(
  File "/usr/lib/python3.8/urllib/request.py", line 569, in error
    return self._call_chain(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.8/urllib/request.py", line 649, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 400: Bad Request

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./src/charm.py", line 142, in <module>
    main(CharmOpenSearch)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/main.py", line 406, in main
    _emit_charm_event(charm, dispatcher.event_name)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/main.py", line 140, in _emit_charm_event
    event_to_emit.emit(*args, **kwargs)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/framework.py", line 278, in emit
    framework._emit(event)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/framework.py", line 722, in _emit
    self._reemit(event_path)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/framework.py", line 767, in _reemit
    custom_handler(event)
  File "./src/charm.py", line 102, in _on_opensearch_pebble_ready
    container.add_layer("opensearch", layer, combine=True)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/model.py", line 1067, in add_layer
    self._pebble.add_layer(label, layer, combine=combine)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/pebble.py", line 879, in add_layer
    self._request('POST', '/v1/layers', body=body)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/pebble.py", line 700, in _request
    response = self._request_raw(method, path, query, headers, data)
  File "/var/lib/juju/agents/unit-opensearch-k8s-0/charm/venv/ops/pebble.py", line 740, in _request_raw
    raise APIError(body, code, status, message)
ops.pebble.APIError: cannot parse layer YAML: service "p" does not exist

[benhoyt]

Sounds good – I’ve renamed the issue title to reflect what we intend to do to fix it. Could add some simple checks into the list fields, or potentially start using a involved schema definition tool like voluptuous

[jameinel]

We should still have a bug that notices if you are using a string instead of a list and error/warn because it is a common pitfall and not what you want. We protect against that sort of misuse elsewhere, and it leads to better information for people writing a charm.

On Sat, May 22, 2021 at 8:39 AM Jon Seager @.***> wrote:

Ah yes, John is right, requires in a list. Nice spot.

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