PROBLEM : Cannot require an Exec

[am-aaron]

hello:

i currently am using Puppet to run some commands in a sequence. there are two sequences of exec resources. we found that we cannot use require => Exec and it does not work at all as expected. here is some sample code.

exec { "exec-AAA":

  command => "/bin/true",

  returns => 0,

  notify  => Exec["exec-BBB"],

}

exec { "exec-BBB":

  refreshonly => true,

  command     => "/bin/false",

  returns     => 0,

  notify      => Exec["exec-CCC"],

}

exec { "exec-CCC":

  refreshonly => true,

  command     => "/bin/touch /tmp/CCC",

  returns     => 0,

}

exec { "exec-DDD":

  require => Exec["exec-CCC"],

  command => "/bin/true",

  returns => 0,

  notify  => Exec["exec-EEE"],

}

exec { "exec-EEE":

  refreshonly => true,

  command     => "/bin/false",

  notify      => Exec["exec-FFF"],

}

exec { "exec-FFF":

  refreshonly => true,

  command     => "/bin/touch /tmp/FFF",

  returns     => 0,

}

ms1:/root/aaron> puppet apply t1.pp

notice: /Stage[main]//Exec[exec-AAA]/returns: executed successfully

err: /Stage[main]//Exec[exec-BBB]: Failed to call refresh: /bin/false returned 1 instead of one of [0] at /root/aaron/t1.pp:11

notice: /Stage[main]//Exec[exec-DDD]/returns: executed successfully

err: /Stage[main]//Exec[exec-EEE]: Failed to call refresh: /bin/false returned 1 instead of one of [0] at /root/aaron/t1.pp:28

notice: Finished catalog run in 0.36 seconds

in the example above, how did Exec["exec-DDD"] run when Exec["exec-CCC"] did not run and Exec["exec-DDD"] require Exec["exec-CCC"]?

ms1:/root/aaron> puppet apply --debug t1.pp

info: Applying configuration version '1349209769'

debug: /Stage[main]//Exec[exec-DDD]/require: requires Exec[exec-CCC]

debug: /Stage[main]//Exec[exec-DDD]/notify: subscribes to Exec[exec-EEE]

debug: /Stage[main]//Exec[exec-BBB]/notify: subscribes to Exec[exec-CCC]

debug: /Stage[main]//Exec[exec-AAA]/notify: subscribes to Exec[exec-BBB]

debug: /Stage[main]//Exec[exec-EEE]/notify: subscribes to Exec[exec-FFF]

debug: /Schedule[never]: Skipping device resources because running on a host

debug: /Schedule[daily]: Skipping device resources because running on a host

debug: /Schedule[monthly]: Skipping device resources because running on a host

debug: /Schedule[puppet]: Skipping device resources because running on a host

debug: /Schedule[hourly]: Skipping device resources because running on a host

debug: /Schedule[weekly]: Skipping device resources because running on a host

debug: Exec[exec-AAA](provider=posix): Executing '/bin/true'

debug: Executing '/bin/true'

notice: /Stage[main]//Exec[exec-AAA]/returns: executed successfully

debug: /Stage[main]//Exec[exec-AAA]: The container Class[Main] will propagate my refresh event

info: /Stage[main]//Exec[exec-AAA]: Scheduling refresh of Exec[exec-BBB]

debug: Exec[exec-BBB](provider=posix): Executing '/bin/false'

debug: Executing '/bin/false'

err: /Stage[main]//Exec[exec-BBB]: Failed to call refresh: /bin/false returned 1 instead of one of [0] at /root/aaron/t1.pp:11

debug: Exec[exec-DDD](provider=posix): Executing '/bin/true'

debug: Executing '/bin/true'

notice: /Stage[main]//Exec[exec-DDD]/returns: executed successfully

debug: /Stage[main]//Exec[exec-DDD]: The container Class[Main] will propagate my refresh event

info: /Stage[main]//Exec[exec-DDD]: Scheduling refresh of Exec[exec-EEE]

debug: Exec[exec-EEE](provider=posix): Executing '/bin/false'

debug: Executing '/bin/false'

err: /Stage[main]//Exec[exec-EEE]: Failed to call refresh: /bin/false returned 1 instead of one of [0] at /root/aaron/t1.pp:28

debug: Class[Main]: The container Stage[main] will propagate my refresh event

debug: Finishing transaction 70054935787440

debug: Storing state

debug: Stored state in 0.06 seconds

notice: Finished catalog run in 0.37 seconds

debug: /File[/var/lib/puppet/rrd]/seluser: Found seluser default 'system_u' for /var/lib/puppet/rrd

debug: /File[/var/lib/puppet/rrd]/selrole: Found selrole default 'object_r' for /var/lib/puppet/rrd

debug: /File[/var/lib/puppet/rrd]/seltype: Found seltype default 'puppet_var_lib_t' for /var/lib/puppet/rrd

debug: /File[/var/lib/puppet/rrd]/selrange: Found selrange default 's0' for /var/lib/puppet/rrd

debug: Finishing transaction 70054934905120

debug: Recieved report to process from ms1

debug: Processing report from ms1 with processor Puppet::Reports::Store

as you can see in the debug run, even though Exec["exec-DDD"] require Exec["exec-CCC"], and the latter does not run, the former runs. what is going on here?

thank you for your time.

have a nice day,

Aaron

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[Miguel Di Ciurcio Filho]

On Tue, Oct 2, 2012 at 5:36 PM, am-aaron <aaron....@ammeon.com> wrote:
>
> exec { "exec-AAA":
> command => "/bin/true",
> returns => 0,
> notify => Exec["exec-BBB"],
> }
> exec { "exec-BBB":
> refreshonly => true,
> command => "/bin/false",
> returns => 0,
> notify => Exec["exec-CCC"],
> }
> exec { "exec-CCC":
> refreshonly => true,
> command => "/bin/touch /tmp/CCC",
> returns => 0,
> }
>
> exec { "exec-DDD":
> require => Exec["exec-CCC"],
> command => "/bin/true",
> returns => 0,
> notify => Exec["exec-EEE"],
> }

I tested your code and indeed, it is a strange behavior.

I guess the root cause of the problem is the `refreshonly => true` of exec-CCC.

My reading of the situation:
- exec-BBB runs and fails, sending nothing to exec-CCC.
- exec-CCC has `refreshonly => true`, since exec-BBB has failed, it
does nothing.
- exec-DDD runs, even having `require => Exec['exec-CCC']` which has
not received a notify because exec-BBB failed.

I did a test using the chaining syntax and the behavior is the same:

Exec['exec-AAA'] ~> Exec['exec-BBB'] ~> Exec['exec-CCC'] -> Exec['exec-DDD']

# puppet apply test.pp

/Stage[main]//Exec[exec-AAA]/returns: executed successfully

Error: /Stage[main]//Exec[exec-BBB]: Failed to call refresh:

/bin/false returned 1 instead of one of [0]

Error: /Stage[main]//Exec[exec-BBB]: /bin/false returned 1 instead of one of [0]

/Stage[main]//Exec[exec-DDD]/returns: executed successfully

Exec['exec-CCC'] does not receive a notification and does not run
because exec-BBB failed. Although, it fulfills the `require`
relationship with Exec['exec-DDD'], which runs.

Note: changing the relationship of Exec['exec-CCC'] and
Exec['exec-DDD'] from `require` para `notify` does not solve the
problem, the behavior is the same.

Very odd. The documentation about `exec` does not say anything about
this behavior of `refreshonly` [1].

[1] http://docs.puppetlabs.com/references/stable/type.html#exec

[Guzman Braso]

I think it's the expected behavior... 

My reading is that if you want Exec["exec-DDD"] being run only when Exec["exec-CCC"] have run, and at the same time, Exec["exec-CCC"] has refreshonly attribute, then it's not require the way, it's set it to refreshonly and tell Exec["exec-CCC"] to notify Exec["exec-DDDD"].

When you require exec-CCC from exec-DDD, puppet will make sure of place exec-CCC before exec-DDD, but if exec-CCC does not run, be it for a ifonly non true, be it for been a refreshonly type without notice, it will continue anyway.

Metaparameters page (http://docs.puppetlabs.com/references/stable/metaparameter.html) says:

>

> This is used purely for guaranteeing that changes to required objects happen before the dependent object"

>

The word "happen" here is tricky, I would say then than happen means "are parsed and run if needed". 

Or... I'm more lost than I thought with puppet and my english still sucks :)

Cheers

Guzman

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[jcbollinger]

The 'require' metaparameter is no different for Exec resources than for any other resource type: foo { 'myfoo': require => Bar['mybar'] } means that when the agent applies the catalog, it must successfully apply resource Bar['mybar'] before it applies resource Foo['myfoo'].  Your issue is basically about what it means to "apply" an Exec.

In simple cases, "applying" an Exec involves running its command, and the success or failure of the resource is based on the command's exit status.

When you set "refreshonly => true" on an Exec resource, that does not make application of the resource conditional.  Puppet will always (attempt to) apply every resource in the catalog it receives.  Instead, "refreshonly => true" makes the steps taken to apply the Exec conditional.  If such an Exec has not been signaled then applying it is a no-op that automatically succeeds.  That's why you are seeing a resource that 'require's Exec['exec-CCC'] being applied even though CCC's command is never run.

Note also that Exec has other parameters that can lead to instances being applied successfully without their commands being run.  The 'creates', 'onlyif', and 'unless' parameters all provide mechanisms for Puppet to decide that an Exec resource is already in sync without running its (main) command.  Applying a resource of any type that is already in sync is also a no-op that automatically succeeds.

Presumably, the question arises from attempts to develop manifests for a particular configuration objective.  If you give us some details about the job you're trying to perform, then we may be able to give you better-targeted advice.


John