While manually running a pattern, the following message may appear:

Error Message RuleError on rule tpl_CustomPattern_body_0 due to: Error while executing a rule -- AttributeError: 'NoneType' object has no attribute 'get' 
Pattern Name CustomPattern
Error Count 1 
Pattern CustomPattern
Internal Error Details File "./__init__.py", line 770, in processEvent File "./rule.py", line 129, in doExecute File "/usr/tideway/var/code/generated_code/CustomPattern/__init__.py", line 1645, in execute if matches('(^edpp.*|^jspp.*|^epp.*|^jpp.*)', dict_get(llr_tpl_si_host, 'name')): File "./library.py", line 100, in dict_get

How to diagnose / troubleshoot this?
 

The important pieces of the error are highlighted below:

Error Message RuleError on rule tpl_CustomPattern_body_0 due to: Error while executing a rule -- AttributeError: 'NoneType' object has no attribute 'get' 
Pattern Name CustomPattern
Error Count 1 
Pattern CustomPattern
Internal Error Details File "./__init__.py", line 770, in processEvent File "./rule.py", line 129, in doExecute File "/usr/tideway/var/code/generated_code/CustomPattern/__init__.py", line 1645, in execute if matches('(^edpp.*|^jspp.*|^epp.*|^jpp.*)', dict_get(llr_tpl_si_host, 'name')): File "./library.py", line 100, in dict_get

In this example, the customer has a pattern called "CustomPattern"

Look in that pattern module, and find this string:  si_host.name

The error is:  AttributeError: 'NoneType' object has no attribute 'get' 

This error means that "si_host" is not defined.  It has a "none" value.  Therefore, it cannot retrieve "name" from si_host.  (The pattern should not refer to "si_host.name" when si_host is "none").

In this particular case, this error can only appear by using "Run Pattern", and pointing to a Manual Group of Software Instances (SI's).  In this Manual Group, some of the SI's no longer have a related Host. (This may occur when aging the Host, but not the SI).

When running a scan, this error cannot appear because by definition, any SI's that are being referred to during discovery do have a related host.

The error can be fixed by adding the following highlighted statements before trying to retrieve an attribute from the "si_host" variable.

si_host := model.host(si);

if not si_host then
    stop();
end if;

log.debug("si host = %si_host.name%");