Migrating to Puppet 4.0

Puppet 4.0 Language
henrik.lindberg@puppetlabs.com
@hel

notice 1 => 1
notice 1 + 2 => syntax error
notice(1 + 2) => 3
notice 1,2,3 => 1 2 3
notice [1,2,3] => 1 2 3
notice [1,2],3 => 1 2 3
notice 5 in [5] => true
notice (4+1) in [5] => error, not a string
notice 5 in [4+1] => false
notice 5.0 in [5] => false
notice(0xff =~ /5/) => false
notice((0xfe+1) =~/5/) => true
notice { a=>10 } => error, no title

Puppet 4.0
• Language Cleanup
– Sanity, Principle of Least Surprise
– Expressions, Expressions, Expressions
• Features
– Misc enhancements
– Resource Expression Features
– Iteration
– Type System / Optional Typing
– Embedded Puppet Templates (EPP)
– Heredoc
– Data in Modules and Environments

Cleanup
• Language Specification – yes we have one
– https://github.com/puppetlabs/puppet-specifications
• Numbers are Numbers
• No magic to-string for =~ !~ in
• Upper case bare words are Type References
• Empty string is not undef (and thus "thruty")
• Interpolation follows specified rules
• +=, []= removed, no more mutation

Signs Your Goldfish is Dead
– Goldfish skin easily cracks
when flexed
– Goldfish is completely
dried out
– Eyes of goldfish are
concave instead of convex
– Pupils of goldfish are gray
– Body parts of the goldfish
are clearly missing

To 4.x from < 3.8 no parser=future
• First Migrate to latest 3.8.x
– Coming from < 3.0 (released 2012)
• Dynamic Scoping removed
• Address Deprecations
– Switch to Directory Environments
• Legacy Environments removed in 4.x
– Use PE Catalog Preview with same code in two environments
• (demos on youtube)
• Turn on future parser in one to help with migration to 4.x Language
• FOSS users can use similar free catalog compare tools (with more manual work)
– Do changes in backwards compatible way
– Update modules
– Gradually migrate nodes – "future parser" production safe

To 4.x from 3.8 with parser=future
• Relatively painless
– Standup a new 4.x master
• Packaging and paths changed in 4.x
– The "all in one" agent
– Same Ruby everywhere
– New location for config files, hiera data etc.
• Enjoy new PE 2015.3 / 4.3 features
– Application Management
– Data in Modules

concat/append/merge/delete 1(6)
• Concatenate Arrays with +
[1,2,3] + [4,5,6] => [1,2,3,4,5,6]
• Merge Hashes with +
{a=>1} + {b=>2} => {a=>1, b=>2}
• Delete with -
[1,2,3] – [2, 3] => [1]
{a=>1, b=>2, c=>3} – [a,c] => {b=>2}
• Append to Array with <<
[1,2,3] << 4 => [1,2,3,4]
[1,2,3] << [4,5,6] => [1,2,3,[4,5,6]]

unfold/splat 2(6)
• Unfold with unary *
$a = [2,3]
$b = [1, *$a, 4] => [1,2,3,4]
• Unfold in case option, selector and call
$a = [1,2,3]
case 1 {
*$a : { # 1 or 2 or 3
}
}
notice *$a => 1,2,3
notice $a => [1,2,3]

substrings 3(6)
• Substring in string
'cd' in "abcde" => true
• Substring with []
"xyzabcdef"[3,3] => "abc"
"xyzabcdef"[3] => "a"
"xyzabcdef"[3,-2] => "abcde"

regexp string/interpolate 4(6)
• Matches with Regexp in String form
$a = "example.com"
$url =~ "http://$a.*"

Error message improvements 5(6)
• Detailed Error Messages
– Semantic validation unless lex or syntax errors
– Outputs position on line
– Can report more than one error

Expression Based Grammar 6(6)
• if, unless, case are expressions
notice if 1 > 2 { true } else { false }
# => false
$a =
case 2 {
1, 2, 3: { yes }
default: { no }
}
# => $a == yes

Local Defaults
file {
default:
mode => '444',
owner => 'admin';
title:
. . . ;
}

Unfold Hash of attributes
file {
default:
* => $defaults_hash;
'tmp/foo':
mode => '666',
* => $params_hash;
}

Create Resources Equiv. in Puppet
Resource[$type] {
default:
* => $defaults_hash;
$titles:
* => $params_hash;
}

LOOOOOOOPS
• Iterate over:
– Arrays
– Hashes
– Strings
– Integer ranges
• Implemented as functions taking callable code
blocks (lambdas) = open design
• Calls can now be expressed from left to right
using '.' notation

each
• Do something with each element
• Returns LHS
[1,2,3].each |$x| { notice $x }
each([1,2,3]) |$x| { notice $x }

map
• Transform each element
• Returns transformed result
[1,2,3].map |$x| { $x*10 }
=> [10,20,30]

filter
• Produces elements that match
• Returns filtered result
[1,2,3].filter|$x| { $x >= 2 }
=> [2,3]

reduce
• Transforms / reduces many to one
• Feeds seed/previous result into next iteration
• Returns transformed result
[1,2,3].reduce |$result, $x| {
$result + $x
}
=> 6

What do you see?
Shout out the answer….

The Puppet Type System
Cow
Integer

Puppet Types
• Puppet Types are first order objects (they can
be assigned and passed around in variables)
• Uses syntax familiar from Resource – i.e. Class,
File, User, where [ ] applied to the type makes
it more specific – e.g. File['foo']

Example Integer
# All integers
Integer
# All integers >=42
Integer[42]
# All integers >=42 and <=142
Integer[42,142]

Automatic type checking!
define mytype(Integer[80,443] $port){
# port guaranteed to be integer
# and between 80 and 443
# otherwise an error
}

Manual type checking!
define mytype($port) {
assert_type(Integer[80,443], $port) |$expected, $got| {
warn("Bad port $got, expected $expected. Using port 80.")
80
}
}
• Code block called if given does not match
• …do what you want, fail, warn, return default

Operations on Type
• Since a Type is a kind of Pattern…
– Match with =~ and !~
– Match in case expression
• Since Types are defined in a hierarchy:
– Compare types with <, <=, >, >=
# is $x an integer ?
$x =~ Integer
# is $t more specific than Integer
$t = Integer[80, 144]
$t < Integer

Type Hierarchy
Any
|- Collection
| |- Array[T]
| | |- Tuple[T*, from, to]
| |
| |- Hash[K, V]
| | |- Struct[{ key => T, ...}]
|
|- Variant[T*]
|- Optional[T]
|
|- Undef
|- Default
|
|- Type[T]

EPP – Templates in Puppet
• Same template markup as ERB
– Logic is Puppet instead of Ruby
AND
• Can be parameterized !
• Use functions
epp(template)
inline_epp(string)
• instead of
template()
inline_template()

Example EPP
$x = 'human'
inline_epp('This is not the <%= $x %> you are looking
for.', { 'x' => 'droid'})
# => 'This is not the droid you are looking for.'
<%- |$x = 'human'| -%>
This is not the <%= $x %> you are looking for.
$x = 'human'
inline_epp('This is not the <%= $x %> you are looking
for.')
# => 'This is not the human you are looking for.'

Puppet Heredoc
• For more detailed control over a block of text
• No, or selected set of escapes
• Interpolation or no interpolation
• Can be syntax checked by parser (JSon in core,
can add plugin language support)
• Control over left margin

Heredoc - Syntax
@( ["]<endtag>["] [:<syntax>] [/<escapes>] )
<text>
[|][-] <endtag>
ENDS-HERE
anything not in <text>
"ENDS-HERE"
with interpolation
:json
syntax check result
/tsrn$L turns on escape
/ turns on all
|
set left margin
-
trim trailing
t tab
s space
r return
n new-line
$ $
L <end of line>

Puppet Heredoc Example
#.........1.........2.........3.........4.........5....
$a = @(END)
This is indented 2 spaces in the source, but produces
a result flush left with the initial 'T'
This line is thus indented 2 spaces.
| END
#.........1.........2.........3.........4.........5....
foo(@(FIRST), @(SECOND))
This is the text for the first heredoc
FIRST
This is the text for the second
SECOND

Ruby API
• 4x Function API
– type checked
– dispatch to impl based on given types
– more powerful
– safer
• Binder
– composable type safe injection
– for plugins and data (e.g. syntax checkers, data
providers)

Summary
• Language Cleanup
• More strict
• New Features
• Better Error Messages
• Iteration
• Type System
• Puppet Templates – EPP
• Heredoc

Links
• github/puppetlabs/puppet-specifications
• http://puppet-on-the-edge.blogspot.com/
• Twitter @hel
• IRC helindbe

Just use PE the next time, ok?

Migrating to Puppet 4.0

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