Transform alerts from one type to another type
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Transform::Alert - Transform alerts from one type to another type


# In your configuration
BaseDir /opt/transalert
<Input test_in>
   Type      POP3
   Interval  60  # seconds (default)
      Username  bob
      Password  mail4fun
      # See Net::POP3->new
      Port     110  # default
      Timeout  120  # default
      TemplateFile  test_in/
      OutputName    test_out
      TemplateFile  test_in/
      Munger        test_in/ MyMunger->munge
      OutputName    test_out
<Output test_out>
   Type          Syslog
   TemplateFile  outputs/
   # See Net::Syslog->new
      Name       TransformAlert
      Facility   local4
      Priority   info
      SyslogPort 514  # default
# On a prompt
> transalert_ctl -c file.conf -l file.log -p


Ever have a need to transform one kind of alert/message into another? For example:

  • Taking a bunch of alert emails and converting them into Syslogs

  • Converting Syslog alerts to SNMP traps

  • Converting SNMP traps to Syslogs

  • Traps to email

  • Anything to anything

Then this platform delivers.

Transform::Alert is a highly extensible platform to transform alerts from anything to anything else. Everything is ran through a configuration file, a couple of templates, and Transform::Alert's daemon app.

Or to show it with a UTF8 drawing, the platform works like this:

Input ──┬── InTemplate ────────────── Output + OutTemplate
        ├── InTemplate + Munger ──┬── Output + OutTemplate
        │                         └── Output + OutTemplate
        ├── InTemplate + Munger ──┬── Output + OutTemplate
        └── InTemplate ───────────┘
Input ──┬── InTemplate ────────────── Output + OutTemplate
        └── InTemplate + Munger ───── Output + OutTemplate

All inputs and outputs are separate modules, so if there isn't a protocol available, they are easy to make. Input templates use a multi-line regular expression with named captures to categorize the variables. Output templates are TT templates with a [% var %] syntax. If you need to transform the data after it's been captured, you can use a "munger" module to play with the variables any way you see fit.


Configuration Format

The configuration uses an Apache-based format (via Config::General). There's a number of elements required within the config file:


BaseDir [dir]

The base directory is used as a starting point for the daemon and any of the relative paths in the config file. The BaseDir option itself can use a relative path, in which case will start at the config path.


<Input [name]>  # one or more
   Type      [type]
   Interval  [seconds]  # optional; default is 60s
   # <ConnOpts> section; module-specific
   # <Template> sections

The Input section specifies a single input source. All Input sections must be named. Multiple Input sections can be specified, but the name must be unique. (Currently, the input name isn't used, but this may change in the future.)

The Type specifies the type of input used. This maps to a Transform::Alert::Input::* class. More information about the different modules be found with the corresponding documentation.

The Interval specifies how frequently the input should be checked (in seconds). Server-based input shouldn't be checked too often, as it might be considered abusive. To prevent overruns, the input will only be re-checked after the interval is complete. (In other words, the "last finished" time is recorded, not the "last start".)

There is one ConnOpts section in each input. The options will be specific to each type, so look there for documentation.

The engine may someday be changed to have multi-processed inputs, but the need isn't immediate right now. (Patches welcome.)


<Input ...>
   <Template>  # one or more
      # Template/File can be optional
      TemplateFile  [file]      # not used with Template
      Template      "[String]"  # not used with TemplateFile
      Munger        [file] [class]->[method]  # optional
      OutputName    test_out    # one or more

All Input sections must have one or more Template sections. As messages are being processed, each message is tested on all of the templates. Input messages will be ran through all templates tied to that input, even if that message matched a previous template. To prevent a message from matching multiple templates, make sure they are reasonably unique.

All templates must either have a TemplateFile or Template option. In most cases, you should stick with file-based templates, as inline templates are whitespace sensitive, and should only be used for single line REs.

If you don't set a Template option, a template file is not used. Without a Munger to validate the hash, these templates will be accepted (and sent to the outputs), as long as it passes data.

The optional Munger option can be used to specify a module used in changing the variables between the input and output. (More details about Mungers further down.) The option itself can be expressed in a number of ways:

Munger My::Munger
Munger  My::Munger
Munger  My::Munger->method
Munger My::Munger->method  # preferred

If a class isn't specified, the first package name found in the file is used. If the method is missing, the default is munge. If there isn't a file specified, it will try to load the class like use/require. (Technically, you could take advantage of the . path in %INC, but it's better to just provide the filename.)

If both Template/File & Munger options are passed, it will test both forms as an AND-based match, testing the text form via template first. This has the benefit of using the input templates as a "gatekeeper", and can be used to delegate different templates to different Mungers. Any named captures from the input template will be passed as a t hash in the variables to the Munger.

The OutputName options provide the name of the Output sources to use after a template match is found. (These sources are defined below.) More that one option means that the alert will be sent to multiple sources.


<Output [name]>  # one or more
   Type          [type]
   TemplateFile  [file]      # not used with Template
   Template      "[String]"  # not used with TemplateFile
   # <ConnOpts> section; module-specific

Like Input, Output sections need to be uniquely named. This name is used with the OutputName option above. Also like Input, the Type functions the same way (mapping to a Transform::Alert::Output::* class), and ConnOpts contains all of the module-specific options.

Similar to Template sections, the Output section must either have a TemplateFile or a Template option. However, you can only use a single template per Output. If you need more, use another section with most of the same options.

Directory Structure

Depending on how large your setup is, you may want to create a directory structure like this:

/opt/transalert          # config, log, PID
/opt/transalert/input1   # various input template directories
/opt/transalert/outputs  # single directory for output templates

If your set up is small, you can get away with a single directory, or at least single input/output directories. Just be sure to use the log/PID options in transalert_ctl, so that they are put in the right directory.

Input Templates

Input templates are basically big multi-line regular expressions. These are NOT /x whitespace-insensitive regular expressions, as those would make copy/pasting large bodies of text more difficult. (There's an assumption that most input templates will have more static text than freeform RE parts.) Besides, you can still use a (?x...) construct for whitespace-insensitivity and comments. Also, leading and trailing whitespace is removed, so stray whitespace should not be an issue there. RE templates are also put into a ^$re$, with begin/end symbols, which can easily be overriden with .*.

Please note that a matched template doesn't stop the matching process, so make sure the templates are unique enough if you don't want to match multiple templates.

Here's an example using an email template:

[\s\S]*\QTo: <>
From: <>
Subject: Email Alert - \E(?<subject>[^\n]+)
Date: (?<date>[^\n]+)
We found a problem on this device:
\QName    :\E (?<name>\w+)
\QProblem :\E (?<problem>[^\n]+)
\QTicket #:\E (?<ticket>\w+)

Of course, this is taking some assumptions about the order and format of headers, but if this is coming from an automated platform that uses the same mail server, there really shouldn't be much change at all. If you need finer control of the verification process, you can make use of Mungers.

Output Templates

Output templates use Template::Toolkit. If you want a quick and dirty lesson on how they work, check out Template::Manual::Syntax. If that is too wordy for you, then just remember that variables are replaced with a [% t.var %] syntax.

The variables passed to the Output (or Munger, if specified) will look like this:

   t => {
      # text form variables acquired from the input RE template
   p => {
      # preparsed hash variables, sent by the Input module

For a structure of the p hash passed, look at the documentation for that input module (under Preparsed Hash). Note that Munger mangling could totally change the structure of the hash passed to the Outputs, depending on what it returns.

Here's an example output template that looks similar to the input one above:

To: [% %]
From: [% t.from %]
Subject: Email Alert - [% t.subject %]
Date: [% %]
We found a problem on this device:
Name    : [% %]
Problem : [% t.problem %]
Ticket #: [% t.ticket %]


Mungers are an optional second piece to the input template structure. Regular expressions, as powerful as they are with finding and capturing information, only do just that. Sometimes you need to warp the information you've captured to fit the mold that the output can use. Or sometimes you need to validate the input in a better fashion than REs can provide. Mungers fit both of those roles.

Mungers are basically freeform Perl modules that transform and/or validate the input data passed to it. Here's an example munger, straight from the test platform:

package TestMunger;
sub munge {
   my ($class, $vars, $tmpl_grp) = @_;
   $vars->{t}{thingy} = delete $vars->{t}{item};
   return int rand(2) ? $vars : undef;

This munger does two (useless) things: change the name of the item variable to thingy, and randomly reject the input. But, this munger could just as easily do anything Perl can do to transform and validate the data.

All mungers are called by their class (ie: TestMunger->munge), so all of them should have a package name. They should also return either undef (as a rejection) or the variable list (as a hashref). If the input ends up with multiple alerts, a munger can also pass an arrayref (of hashrefs), and they will be sent to the outputs individually.

A munger could also become the primary piece for input transformation/validation by not specifying a Template option.

Mungers are also passed the TemplateGrp object. This is mostly used as a way to hook into the log, like:

$tmpl_grp->log->debug("Munger didn't like Message Body");

Variable Passing

If you're still confused on the variable passing, look at it this way:

Input ──┬── $text ───── InTemplate ───── t => { %+ } ──┬── Munger ───── { ??? } ───── Out...
        └── $hash ────────────────────── p => $hash  ──┘
Input ──┬── $text ────────────────────── t => {    } ──┬── Munger ───── { ??? } ───── Out...
        └── $hash ────────────────────── p => $hash  ──┘
Input ──┬── $text ───── InTemplate ───── t => { %+ } ──┬───────────────────────────── Out...
        └── $hash ────────────────────── p => $hash  ──┘
Input ──┬── $text ────────────────────── t => {    } ──┬── Munger ───── [ { ??? }, ── Out...
        └── $hash ────────────────────── p => $hash  ──┘                  { ??? }, ── Out...
                                                                          { ??? } ] ─ Out...
...OutTemplate ───── $str ───── Output


  • One would consider this a grand feat of over-engineering, which doesn't apply to every single protocol cleanly. For example,

email input templates alone probably shouldn't be used, as header order might change, and the SNMP I/O doesn't translate to text
very well.  YMMV.


  • Moar I/O:

Inputs            Outputs
------            -------
File::CSV         File::CSV
File::Text        File::Text
  • Pegex support for input templates, maybe when we stop playing with the syntax :)

  • Multi-threaded and/or -processed inputs/outputs


The project homepage is

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit to find a CPAN site near you, or see


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Bugs / Feature Requests

Please report any bugs or feature requests via


Brendan Byrd <>


This software is Copyright (c) 2013 by Brendan Byrd.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)