YAML Idiosyncrasies¶

One of Salt's strengths, the use of existing serialization systems for representing SLS data, can also backfire. YAML is a general purpose system and there are a number of things that would seem to make sense in an sls file that cause YAML issues. It is wise to be aware of these issues. While reports or running into them are generally rare they can still crop up at unexpected times.

Spaces vs Tabs¶

YAML uses spaces, period. Do not use tabs in your SLS files! If strange errors are coming up in rendering SLS files, make sure to check that no tabs have crept in! In Vim, after enabling search highlighting with: :set hlsearch, you can check with the following key sequence in normal mode(you can hit ESC twice to be sure): /, Ctrl-v, Tab, then hit Enter. Also, you can convert tabs to 2 spaces by these commands in Vim: :set tabstop=2 expandtab and then :retab.

Indentation¶

The suggested syntax for YAML files is to use 2 spaces for indentation, but YAML will follow whatever indentation system that the individual file uses. Indentation of two spaces works very well for SLS files given the fact that the data is uniform and not deeply nested.

Nested Dicts (key=value)¶

When dicts are more deeply nested, they no longer follow the same indentation logic. This is rarely something that comes up in Salt, since deeply nested options like these are discouraged when making State modules, but some do exist. A good example is the context and default options in the file.managed state:

/etc/http/conf/http.conf:
  file:
    - managed
    - source: salt://apache/http.conf
    - user: root
    - group: root
    - mode: 644
    - template: jinja
    - context:
        custom_var: "override"
    - defaults:
        custom_var: "default value"
        other_var: 123

Notice that the spacing used is 2 spaces, and that when defining the context and defaults options there is a 4 space indent. If only a 2 space indent is used then the information will not be loaded correctly. If using double spacing is not desirable, then a deeply nested dict can be declared with curly braces:

/etc/http/conf/http.conf:
  file:
    - managed
    - source: salt://apache/http.conf
    - user: root
    - group: root
    - mode: 644
    - template: jinja
    - context: {
      custom_var: "override" }
    - defaults: {
      custom_var: "default value",
      other_var: 123 }

True/False, Yes/No, On/Off¶

PyYAML will load these values as boolean True or False. Un-capitalized versions will also be loaded as booleans (true, false, yes, no, on, and off). This can be especially problematic when constructing Pillar data. Make sure that your Pillars which need to use the string versions of these values are enclosed in quotes.

Integers are Parsed as Integers¶

NOTE: This has been fixed in salt 0.10.0, as of this release passing an integer that is preceded by a 0 will be correctly parsed

When passing integers into an SLS file, they are passed as integers. This means that if a state accepts a string value and an integer is passed, that an integer will be sent. The solution here is to send the integer as a string.

This is best explained when setting the mode for a file:

/etc/vimrc:
  file:
    - managed
    - source: salt://edit/vimrc
    - user: root
    - group: root
    - mode: 644

Salt manages this well, since the mode is passed as 644, but if the mode is zero padded as 0644, then it is read by YAML as an integer and evaluated as an octal value, 0644 becomes 420. Therefore, if the file mode is preceded by a 0 then it needs to be passed as a string:

/etc/vimrc:
  file:
    - managed
    - source: salt://edit/vimrc
    - user: root
    - group: root
    - mode: '0644'

YAML does not like "Double Short Decs"¶

If I can find a way to make YAML accept "Double Short Decs" then I will, since I think that double short decs would be awesome. So what is a "Double Short Dec"? It is when you declare a multiple short decs in one ID. Here is a standard short dec, it works great:

vim:
  pkg.installed

The short dec means that there are no arguments to pass, so it is not required to add any arguments, and it can save space.

YAML though, gets upset when declaring multiple short decs, for the record...

THIS DOES NOT WORK:

vim:
  pkg.installed
  user.present

Similarly declaring a short dec in the same ID dec as a standard dec does not work either...

ALSO DOES NOT WORK:

fred:
  user.present
  ssh_auth.present:
    - name: AAAAB3NzaC...
    - user: fred
    - enc: ssh-dss
    - require:
      - user: fred

The correct way is to define them like this:

vim:
  pkg.installed: []
  user.present: []

fred:
  user.present: []
  ssh_auth.present:
    - name: AAAAB3NzaC...
    - user: fred
    - enc: ssh-dss
    - require:
      - user: fred

Alternatively, they can be defined the "old way", or with multiple "full decs":

vim:
  pkg:
    - installed
  user:
    - present

fred:
  user:
    - present
  ssh_auth:
    - present
    - name: AAAAB3NzaC...
    - user: fred
    - enc: ssh-dss
    - require:
      - user: fred

YAML support only plain ASCII¶

According to YAML specification, only ASCII characters can be used.

Within double-quotes, special characters may be represented with C-style escape sequences starting with a backslash ( \ ).

Examples:

- micro: "\u00b5"
- copyright: "\u00A9"
- A: "\x41"
- alpha: "\u0251"
- Alef: "\u05d0"

List of usable Unicode characters will help you to identify correct numbers.

Python can also be used to discover the Unicode number for a character:

repr(u"Text with wrong characters i need to figure out")

This shell command can find wrong characters in your SLS files:

find . -name '*.sls'  -exec  grep --color='auto' -P -n '[^\x00-\x7F]' \{} \;

Underscores stripped in Integer Definitions¶

If a definition only includes numbers and underscores, it is parsed by YAML as an integer and all underscores are stripped. To ensure the object becomes a string, it should be surrounded by quotes. More information here.

Here's an example:

>>> import yaml
>>> yaml.safe_load('2013_05_10')
20130510
>>> yaml.safe_load('"2013_05_10"')
'2013_05_10'