At its most basic, this is nothing more than an array or hash lookup,
but when used in conjunction with map, it is very useful. For example,
while constructing an "ssh-keyscan …" command to update known_hosts on
all hosts in a group, one can get a list of IP addresses with:
groups['x']|map('extract', hostvars, 'ec2_ip_address')|list
This returns hostvars[a].ec2_ip_address, hostvars[b].ec2_ip_address, and
so on. You can even specify an array of keys for a recursive lookup, and
mix string and integer keys depending on what you're looking up:
['localhost']|map('extract', hostvars, ['vars','group_names',0])|first
== hostvars['localhost']['vars']['group_names'][0]
== 'ungrouped'
Includes documentation and tests.
The inventory pattern delimiter used in the examples switches between the comma and colon. While both are valid I've found this throws off new users so I've modified the examples to consistently use a colon, the more common of the two in my experience.
Noticed that the v1 variable precedence docs list facts discovered as having a lower precedence than inventory variables. It is in reality the other way around. The v2 section gets this right.
I found it difficult to find documentation for how to pull from a git-based scm that wasn't github. The only way I could find this option was to dig through the google-group.
This is a confusing part of roles and tags. Most people assume that tagging a role means that the tagged tasks inside the role will run based on the tags specified. But in reality, it tags the whole role with those tags.
Closes#12990.
Alternative to #12992
This PR excludes all attributes of the following data types: lists,
tuples, dicts, sets, integers, floats, strings and Unicode objects.
It is expected that only the attributes of dicts and sets would cause an
problem like in #12990.
I was caught out by the different behaviour of lookups & local tasks, and could not find the difference documented anywhere at all, so I took the liberty of proposing this change.
Lookups are always relative to the role or play.
Local tasks are relative to the cwd from which you execute.
