Telephone +44(0)1524 64544
Email: info(at)shadowcat.co.uk

Sat Dec 22 00:30:00 2012

Slides for the talk tak at lpw-2011

-

The First
Thing Tak
Did ...

-

Tak?

-

Fab

-

fabfile.org

-

Mass SSH

-

Runs ...
commands

-

local()
remote()

-

BORING

-

Sysadmins
like it

-

Ok ...

-

mcollective

-

Message
queue backed

-

Runs ...
commands

-

BORING

-

(there's
also Rex
in perl)

-

What's the
general
concept?

-

Messaging
Jobs

-

Ok. Step
back.

-

"Run [this]
on [these]
systems"

-

Semi
independent
agents

-

Running
code on
remote
systems

-

But ...

-

Dependency
management

-

Dependency
management
for ad-hoc
code sucks

-

App::FatPacker

-

Have to
pack each
script ...

-

... and
copy it
to all
the hosts

-

BORING

-

perl
to the
rescue

-

__END__

-

"script is
done now"

-

Which
means ...

-

  ssh host
    perl -

-

  cat script
  echo __END__

-

Then
what?

-

The Second
Thing Tak
Did

-

Need a
protocol

-

Simple

-

Human
readable

-

Already
written

-

HTTP?

-

Ugh.

-

Line
based?

-

Ok but ...

-

Not writing
a parser

-

JSON!

-

  [ "type", "payload", "here" ]

-

Reliability

-

Three
message
types

-

Message.
Request.
Response.

-

Wait.

-

What
about
progress?

-

Response
=
Progress
Result

-

Message
Request
Progress
Result

-

Why have
requests
at the
protocol
level?

-

Requests
must
always
complete

-

Tracking

-

Tracking
across
hosts

-

Tracking
over
time

-

Message
routing

-

Central
dictionary?

-

Why?

-

Opaque
routing

-

  [ "request",
    "service-name",
    "type",
    "payload",
     ...
  ]

-

Service
name?

-

Router

-

  my ($self, $service_name, @msg) = @_;
  $services{$service_name}->send(@msg);

-

Meta
service

-

  [ "request",
    "meta",
    "register",
    "service-name",
    "Service::Class",
    ...
  ]

-

Client

-

  # do or die()
  $client->do(
    service_name
    => request_type
    => @payload
  );

-

  # result object
  $client->result_of(
    service_name
    => request_type
    => @payload
  );

-

  # return data or throw
  $result->get;
  # get error if any
  $result->exception;

-

  my $req = $client->start({
    on_result => sub { ... },
    on_progress => sub { ... },
  }, @payload);

-

  # And finally
  Tak->await_all(
    @requests
  );

-

-

A small
diversion

-

Event
loops

-

  while (my $line = <$fh>) {
    ...
  }

-

Parallel

-

Arse.

-

POE
IO::Async
AnyEvent

-

More than
I needed

-

Steal from
AnyEvent?

-

AnyEvent::Impl::Perl

-

select()

-

Handle
vectors

-

vec() ?

-

Nooo ...

-

  # we parse the bitmask by first
  # expanding it into a string of bits
  for (unpack "b*", $vec[$_]) {

-

  # and then repeatedly matching
  # a regex against it
  while (/1/g) {

-

  # and use the resulting string position as fd
  $_ && $_->[2]()
     for @{ $fds->[W][(pos) - 1] || [] };

-

....

-

....
....

-

Fuck that,
I'll just use
IO::Select

-

-

tak

-

App::Tak

-

Tak::Script

-

Custom
commands

-

Tak::MyScript

-

Takfile

-

  tak -h user@host command

-

  sub each_command {
    my ($self, $remote) = @_;

-

$remote?

-

ConnectorService

-

Net::OpenSSH

-

(and later
Net::SSH::Perl
for win32)

-

  $ssh->open2('perl', '-');

-

  $kid_in->print(
    io($fatscript)->all,
    "__END__\n"
  );

-

  $fatscript?

-

  fatpack tree $(fatpack packlists-for
    strictures.pm Moo.pm Algorithm/C3.pm
    MRO/Compat.pm Class/C3.pm JSON/PP.pm
    Log/Contextual.pm Data/Dumper/Concise.pm)

-

  fatpack tree $(fatpack packlists-for
    strictures.pm Moo.pm Algorithm/C3.pm
    MRO/Compat.pm Class/C3.pm JSON/PP.pm
    Log/Contextual.pm Data/Dumper/Concise.pm)
  fatpack file

-

  fatpack tree $(fatpack packlists-for
    strictures.pm Moo.pm Algorithm/C3.pm
    MRO/Compat.pm Class/C3.pm JSON/PP.pm
    Log/Contextual.pm Data/Dumper/Concise.pm)
  fatpack file
  echo "use Tak::STDIOSetup;
    Tak::STDIOSetup->run;"

-

  $remote->do(
    meta => ensure
    => eval_service
    => 'Tak::EvalService'
  );

-

Wait.

-

We didn't
fatpack
that.

-

Far side
has a
loopback
router

-

  $local->ensure(
    module_sender
    => 'Tak::ModuleSender'
  );

-

  $remote->ensure(
    module_loader => 'Tak::ModuleLoader',
    expose => {
      module_sender
      => [ 'remote', 'module_sender' ]
    }
  );

-

expose
passes
service
references

-

no global
router
required

-

Tak::ModuleSender

-

  sub handle_source_for {
    my ($self, $module) = @_;
    my $io = (find module);
    return scalar $io->all;
  }

-

  Tak::ModuleLoader

-

  sub {
    my $result = (ask sender);
    my $code = $result->get;
    open my $fh, '<', \$code;
    return $fh;
  }

-

  push @INC, $hook;

-

  sub each_exec {
    my ($self, $remote, @cmd) = @_;
    $remote->ensure(
      command_service
      => 'Tak::CommandService'
    );

-

  my $result = $remote->do(
    command_service
    => exec
    => \@cmd
  );

-

  sub handle_exec {
    my ($self, $command) = @_;
    my $code;
    my ($stdout, $stderr) = capture {
      $code = runx(EXIT_ANY, @$command);
    };

-

Sequential

-

:(

-

  sub every_exec {
    my ($self, $remotes, @command) = @_;
    my @requests;
    foreach my $remote (@$remotes) {
      push @requests, $remote->start(
        ...
      );
    }
    Tak->await_all(@requests);
  }

-

Streaming?

-

  on_progress
    => sub {

-

Optional
streaming

-

  sub every_exec (stream|s) {
    my ($self, $remotes, $options, @command) = @_;

-

Getopt::Long
spec in
prototype!

-

  sub every_exec (stream|s) {
    my ($self, $remotes, $options, @command) = @_;
    ...
    if ($options->{stream}) {

-

  tak -h user@host
    exec --stream tail -f ...

-

  tak -h user@host
    exec -s tail -f ...

-

Running
perl code
remotely?

-

Tak::ObjectService

-

  my $oc = Tak::ObjectClient->new(
    remote => $remote
  );
  my $obj = $oc->new_object(
    $class => \%args_to_new
  );

-

  $json->convert_blessed;

-

  $json->convert_blessed;
  local *UNIVERSAL::TO_JSON = sub {

-

  $json->decode(
    $json->encode($msg)
  );

-

  $json->filter_json_single_key_object(
    __proxied_object__ => sub { ... }
  );

-

Local proxies
send method
call requests

-

  sub each_get_homedir {
    my ($self, $remote) = @_;
    my $oc = Tak::ObjectClient->new(
      remote => $remote
    );
    my $dot = $oc->new_object(
      'Path::Class::Dir'
    );
    $home = $dot->absolute->stringify;

-

Experimentation

-

Run, swear,
tweak, run,
swear ...

-

tinyrepl

-

Eval::WithLexicals

-

Pure perl

-

Fatpackable

-

Tak::EvalService

-

  eval {
    ($stdout, $stderr) = capture {
      @ret = $eval->eval($perl);
    };
  };

-

  Tak::REPL->new(
    remote => $remote
  )->run

-

  $ tak -h user@host repl
  re.pl$

-

Tak went
to CPAN
... finally

-

#perl-tak
exists on
freenode

-

Try it.
Break it.
Tell me
about it.

-

The Third
Thing Tak
Did

-

__END__

-

Thank You
IRC:mst
mst@shadowcat.co.uk
@shadowcat_mst