Puppet Language 4.0 - Henrik Lindberg, Puppet Labs

2. Yamata
no
Orochi

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

11. 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

13. Puppet
4.0
• Language
Cleanup
– Sanity,
Principle
of
Least
Surprise
– Expressions,
Expressions,
Expressions
• Features
– Misc
enhancements
– Resource
Expression
Features
– IteraGon
– Type
System
/
OpGonal
Typing
– Embedded
Puppet
Templates
(EPP)
– Heredoc

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

16. Misc
new
features
1(7)
• 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}

17. Misc
new
features
2(7)
• Append
to
Array
with
<<
[1,2,3] << 4 => [1,2,3,4]
[1,2,3] << [4,5,6] => [1,2,3,[4,5,6]]

18. Misc
new
features
3(7)
• Unfold
with
unary
*
$a = [2,3]
$b = [1, *$a, 4] => [1,2,3,4]
• Unfold
in
case
opGon,
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]

19. Misc
new
features
4(7)
• Substring
in
string
'cd' in "abcde" => true
• Substring
with
[]
"xyzabcdef"[3,3] => "abc"
"xyzabcdef"[3] => "a"
"xyzabcdef"[3,-2] => "abcde"

20. Misc
new
features
5(7)
• Matches
with
Regexp
in
String
form
$a = "example.com"
$url =~ "http://$a.*"

21. Misc
new
features
6(7)
• Detailed
Error
Messages
– SemanGc
validaGon
unless
lex
or
syntax
errors
– Outputs
posiGon
on
line
– Can
report
more
than
one
error

22. Expression
Based
Grammar
6(7)
• if,
unless,
case
are
expressions
notice if 1 > 2 { true } else { false }
# => false
$a =
case 2 {
1, 2, 3: { yes }
default: { no }
}
# => $a == yes

23. Resource
Expression

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

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

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

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

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

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

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

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

33. And
more

37. E-­‐I-­‐E-­‐I-­‐O

39. E-­‐I-­‐E-­‐I-­‐O

41. E-­‐I-­‐E-­‐I-­‐O

44. E-­‐I-­‐E-­‐I-­‐O

46. The
Puppet
Type
System
Cow
Integer

47. 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']

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

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

50. More
advanced
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

51. OperaGons
on
Type
• Since
a
Type
is
a
kind
of
PaQern…
– 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

52. Type
Hierarchy
Any
|- Scalar
| |- Numeric
| | |- Integer[from, to]
| | |- Float[from, to]
| |
| |- String[from, to]
| | |- Enum[*strings]
| | |- Pattern[*patterns]
| |
| |- Boolean
| |- Regexp[pattern_string]

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

54. Type
Hierarchy
Any
|- CatalogEntry
| |- Resource[type_name, title]
| |- Class[class_name]
|
|- Undef
|- Data
| |- Scalar
| |- Array[Data]
| |- Hash[Scalar, Data]
| |- Undef

55. EPP

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

57. Example
EPP
$x = 'human'
inline_epp('This is not the <%= $x %> you are looking
for.')
# => 'This is not the human you are looking for.'
$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.

58. Heredoc

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

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

61. 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

62. Ruby
API

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

64. Summary
• Language
Cleanup
• More
strict
• New
Features
• BeQer
Error
Messages
• IteraGon
• Type
System
• Puppet
Templates
–
EPP
• Heredoc

65. In
pracGce
• Run
now
with
–parser
future
• Fix
deprecaGons
and
issues
• Make
backwards
compaGble
changes
and
conGnue
in
producGon
on
3x
• Test
carefully
and
conGnue
running
on
what
will
be
Puppet
4.0
• 4.0
expected
release
before
end
of
the
year

67. Links
• github/puppetlabs/puppet-­‐specificaGons
• hQp://puppet-­‐on-­‐the-­‐edge.blogspot.com/
• TwiQer
@hel
• IRC
helindbe