dsl quest: a wat safari - puppetconf 2013

Nick’s DSL Quest:WAT SafariNick FagerlundTechnical Writer | Puppet Labs @nfagerlund

Friday, August 23, 13

puppetconf.com #puppetconf

So okay, there I was.



When I first got here, we had this “language

tutorial.”



It was a bit of a mess.(“Additional language features…?”)



The Puppet language accreted over time.



(And so did the docs.)



So I had a good/bad idea.



Here’s what I found.



$subj = {t => 'r', u => 'e'}

notice(str2bool("$subj"))

T to the R



$subj = {t => 'r', u => 'e'}

notice(str2bool("$subj"))

true

T to the R



@notify {'one tag': tag => 'one',}@notify {'two tags': tag => ['one', 'two'], #before => Notify['three tags']} @notify {'three tags': tag => ['one', 'two', 'three'], noop => undef,}

Let’s talk about collectors



Notify <| tag == 'one' |>

Notice: Compiled catalog for magpie.lan in environment production in 0.11 secondsNotice: one tagNotice: /Stage[main]//Notify[one tag]/message: defined 'message' as 'one tag'Notice: three tagsNotice: /Stage[main]//Notify[three tags]/message: defined 'message' as 'three tags'Notice: two tagsNotice: /Stage[main]//Notify[two tags]/message: defined 'message' as 'two tags'




Notify <| 'one' == tag |>

Error: Could not parse for environment production: Syntax error at 'one'; expected '|>' at /Users/nick/Documents/manifests/collector-‐search.pp:29 on node magpie.lan




Notify <| tag == ['one', 'two'] |>

Notice: Compiled catalog for magpie.lan in environment production in 0.09 secondsNotice: one tagNotice: /Stage[main]//Notify[one tag]/message: defined 'message' as 'one tag'Notice: three tagsNotice: /Stage[main]//Notify[three tags]/message: defined 'message' as 'three tags'Notice: two tagsNotice: /Stage[main]//Notify[two tags]/message: defined 'message' as 'two tags'Notice: Finished catalog run in 0.17 seconds




Notify <| tag != ['one', 'two'] |>

Notice: Compiled catalog for magpie.lan in environment production in 0.09 secondsNotice: three tagsNotice: /Stage[main]//Notify[three tags]/message: defined 'message' as 'three tags'Notice: two tagsNotice: /Stage[main]//Notify[two tags]/message: defined 'message' as 'two tags'Notice: Finished catalog run in 0.18 seconds




CONCLUSION:“==” != “==”



class class { notify {'hey it worked':}}

include class

Results

Classy




include class

Error: Could not parse for environment production: Syntax error at 'class' at /Users/nick/Documents/manifests/class_class.pp:6 on node magpie.lan

Classy




include "class"

Classy




include "class"

Notice: Compiled catalog for magpie.lan in environment production in 0.09 secondsNotice: hey it workedNotice: /Stage[main]/Class/Notify[hey it worked]/message: defined 'message' as 'hey it worked'Notice: Finished catalog run in 0.19 seconds

Classy



class parent { define doessomething { notice("parentvar is set, in the parent::doessomething define") } class whoa { notice("Okay that works w/ classes too") } $otherparentvar = "haha whoa"}search('parent')doessomething{'something':}include whoanotice($otherparentvar) # This one doesn't work though, because it attaches the NAMESPACE, not the scope.

Search???



class parent { define doessomething { notice("parentvar is set, in the parent::doessomething define") } class whoa { notice("Okay that works w/ classes too") } $otherparentvar = "haha whoa"}search('parent')doessomething{'something':}include whoanotice($otherparentvar) # This one doesn't work though, because it attaches the NAMESPACE, not the scope.

It dumps a random namespace into the local namespace???

Search???



(This is still in Puppet 3.2.)

(photo via http://weheartit.com/entry/

68358166)


http://weheartit.com/entry/68358166







[ Notify['first'], Notify['second'] ]

It’s an array of resource references, right?

Have you seen this syntax?



Notify[ 'first', 'second' ]

???

How about this one?



Notify[ ['first', 'second'] ]

(Okay, it ends up being the same as the last one for some reason.)

How about this one?



# OKrequire => Notify['first', 'second']require => [ Notify['first'], Notify['second'] ]Notify['first', 'second'] -‐> Notify['third']

# BAD[ Notify['first'], Notify['second'] ] -‐> Notify['third']

?????!!

They all look kind of similar?



# OKNotify['first', 'second'] { message => 'Adding a message to these.'}

# BAD[ Notify['first'], Notify['second'] ] { message => 'Adding a message to these.'}

?????!!

They all look kind of similar?



So, these are two completely different

syntaxes. (I named the non-array one “multi-

references.)



class bar { notice("From class bar")}class foo::bar { notice("From class foo::bar")}class foo { include bar}include foo

Include bar... but only as a last resort



class bar { notice("From class bar")}class foo::bar { notice("From class foo::bar")}class foo { include bar}include foo

Notice: Scope(Class[Foo::Bar]): From class foo::bar

(this is bug #2053.)

Include bar... but only as a last resort



# Is the == operator case-‐sensitive? NOnotice( 'eat' == 'EAt' )

# Is the 'in' operator case-‐sensitive? YESnotice( 'eat' in 'EAten' )

Notice: Scope(Class[main]): trueNotice: Scope(Class[main]): false

Case sensitivity training



ANYWAY



# The $is_virtual fact is false on this machineif $is_virtual { notice("Guess this is a virtual machine!")}

Falseness is truth



# The $is_virtual fact is false on this machineif $is_virtual { notice("Guess this is a virtual machine!")}

Notice: Scope(Class[main]): Guess this is a virtual machine!

Falseness is truth



(Use the str2bool() function from

puppetlabs/stdlib)



This, of course, escalated quickly.



Code

Results

What IS truth, anyway?



$x = 5$y = 3notice("Value of x is ${x}")

You’ve seen this before.

Express yourself



$x = 5$y = 3notice("Five by three is ${$x * $y}")

Express yourself



$x = 5$y = 3notice("Five by three is ${$x * $y}")

Notice: Scope(Class[main]): Five by three is 15

Express yourself



$mystring = "Nothing in particular"notice("But it was ${$mystring =~ /thing/}")

Notice: Scope(Class[main]): But it was true

Express yourself

Whoa



notice("This time with an in statement: Is there a thing in nothing? ${"thing" in $mystring} so yeah")

Notice: Scope(Class[main]): This time with an in statement: Is there a thing in nothing? true so yeah

Express yourself



notice("There's a function operand in here: ${ fqdn_rand(30) + '90' } so yeah")

WELL, at least THAT one doesn’t work.

Express yourself



notice("Variable with doubled sigil: ${ $x} so yeah")

notice("Singular sigil, but with wacky spacing: ${ x} so yeah")

Notice: Scope(Class[main]): Variable with doubled sigil: 5 so yeahNotice: Scope(Class[main]): Singular sigil, but with wacky spacing: 5 so yeah

Express yourself



notice("Yo dawg, I heard you like ${"strings, so I put a string in your"} string")

Sorry for partying like it’s 200X, but anyway yeah, that totally works.

Express yourself



# What about this? notice("Twenty by eighty is ${ 20 * 80 } so yeah")

Error: left operand of * is not a number

Express yourself



notice("Twenty by eighty is ${ '20' * '80' } so yeah")

Notice: Scope(Class[main]): Twenty by eighty is 1600 so yeah

Express yourself



And at this point I was like



(It turns out the first bareword in an interpolation block gets silently

turned into a variable, so 20 became $20, which would be a regex capture variable except we weren’t inside a

conditional so it was undef???)



So then I was like



yeah



file {'file1': path => '/tmp/file1', ensure => file, alias => ['othername', 'fourthname'],}

file {'file2': path => '/tmp/file2', ensure => file, before => File['othername'],}

Let’s talk about aliases



file {'file1': path => '/tmp/file1', ensure => file, alias => ['othername', 'fourthname'],}

file {'file2': path => '/tmp/file2', ensure => file, before => File['othername'],}

This works fine.




file {'file1': alias => ['othername', 'fourthname'],}file {'file2':}

File['file2'] -‐> File['othername']

Error: Could not find resource 'File[othername]' for relationship from 'File[file2]' on node magpie.lan

So it works in metaparameters, but not in chaining statements.

Okay!




@file {'file1': path => '/tmp/file1', ensure => file, alias => ['othername', 'fourthname'],}

realize File['othername']

Nope!





realize File['/tmp/file1']

Nope!





File <| alias == 'fourthname' |>

PURRS LIKE A KITTEN!




Anyway, what did I learn?

(In the larger sense, not in the str2bool({t => ‘r’, u =>

‘e’}) sense.)



Do science to it.



Long-lived systems get weird.



Talk to the old-timers.



WAT brings us together!



(Pause here for general theory of the social capital

of WAT in engineering cultures.)



And venting about WAT can keep your morale up.

Because c’mon.

That’s pretty funny.



https://github.com/nfagerlund/evil-made-manifest

(photo via http://taterpie.tumblr.com/post/56826040138/thats-an-awesome-

shot)












Thank YouNick FagerlundTechnical Writer | Puppet Labs @nfagerlund

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dsl quest: a wat safari - puppetconf 2013

Technology

finished catalog

classes

compiled catalog

puppetconf

lets talk

haha whoa

wacky spacing

doubled sigil