This change is similar to https://github.com/ansible/ansible/pull/10465
It extends the logic there to also support none types. Right now if you have
a '!!null' in yaml, and that var gets passed around, it will get converted to
a string.
eg. defaults/main.yml
```
ENABLE_AWESOME_FEATURE: !!null # Yaml Null
OTHER_CONFIG:
secret1: "so_secret"
secret2: "even_more_secret"
CONFIG:
hostname: "some_hostname"
features:
awesame_feature: "{{ ENABLE_AWESOME_FEATURE}}"
secrets: "{{ OTHER_CONFIG }}"
```
If you output `CONFIG` to json or yaml, the feature flag would get represented in the output
as a string instead of as a null, but secrets would get represented as a dictionary. This is
a mis-match in behaviour where some "types" are retained and others are not. This change
should fix the issue.
I also updated the template test to test for this and made the changes to v2.
Added a changelog entry specifically for the change from empty string to null as the default.
Made the null representation configurable.
It still defaults to the python NoneType but can be overriden to be an emptystring by updating
the DEFAULT_NULL_REPRESENTATION config.
first off, we add an oddly slow basic test of 10k item inventory
Before:
```
Ran 229 tests in 13.214s
OK
real 0m13.403s
user 0m12.106s
sys 0m1.155s
```
After:
```
Ran 230 tests in 21.328s
OK
real 0m21.516s
user 0m20.099s
sys 0m1.275s
```
since that seems like a bit long for the test to add to runtime, lets profile
`python -m cProfile -s time ./bin/ansible all -i test/units/inventory_test_data/huge_range --list-hosts`
Before:
```
1272607 function calls (1259689 primitive calls) in 8.497 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
10000 4.393 0.000 4.396 0.000 __init__.py:395(_get_host)
20000 2.695 0.000 2.697 0.000 __init__.py:341(__append_host_to_results)
40369 0.113 0.000 0.113 0.000 {posix.lstat}
50006 0.102 0.000 0.153 0.000 __init__.py:1490(combine_vars)
40008 0.089 0.000 0.202 0.000 __init__.py:1546(_load_vars_from_path)
20195 0.088 0.000 0.088 0.000 {posix.stat}
10011 0.087 0.000 0.087 0.000 {posix.getcwd}
```
The top two lines are promising optimization targets
- populate Inventory's host cache more in _get_host, as we are looping
over all the groups anyways.
- eliminate duplicate check of whether we've already included a host
in the construction around __append_host_to_results we can infer
presence of a host in the results list implies the presence of its
name in the hostnames set, allowing us to only to the less expensive
of the two checks
After:
```
1252610 function calls (1239692 primitive calls) in 1.320 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
40369 0.105 0.000 0.105 0.000 {posix.lstat}
50006 0.094 0.000 0.141 0.000 __init__.py:1490(combine_vars)
40008 0.081 0.000 0.184 0.000 __init__.py:1546(_load_vars_from_path)
10011 0.080 0.000 0.080 0.000 {posix.getcwd}
20195 0.074 0.000 0.074 0.000 {posix.stat}
10002 0.069 0.000 0.261 0.000 __init__.py:1517(load_vars)
```
* Speed up serialization of hostvars by simply using the internal
dictionary used for cached lookups
* Use blocking gets/puts on queues instead of spin locking
* Merge sequential implicitly created blocks
