dogwrap: Trim output

[gnarf]

When a command has output that makes the message exceed the 4000 character limit for events, the formating gets completely lost and so does the notifications that are appended ( #88 )

There should probably be a strategy in place to trim the output to something that fits in an event. I'd suggest it be configurable.

Total size of the event can not be > 4000 characters, so a few different strategies make sense to me

• tail - Show only the last ~3500 characters (4k - however many bytes are used in headers/notifications/etc), for when the commands output really only matters what comes at the end
• head - show only the first ~3500 characters (^^^), for when the start of the command is really all that matters
• both (default?)- Take ~1000 from the top and ~2500 from the bottom with a ...trimmed... in the middle, the first 1/3rd of the budget on the top, and the other 2 thirds on the bottom.

[yannmh]

Thanks a lot for the detailed explanations @gnarf !

I like the idea of making the 'trim' strategy configurable. I reckon 'head' should probably be the default behavior.

We'll work on it for the next version 🚀

[gnarf]

Considering the errors are USUALLY at the bottom when there are errors, I
like the one that mixes a bit of head and a bit of tail best

On Mon, Oct 19, 2015 at 6:55 PM, Yann notifications@github.com wrote:

Thanks a lot for the detailed explanations @gnarf
https://github.com/gnarf !

I like the idea of making the 'trim' strategy configurable. I reckon
'head' should probably be the default behavior.

We'll work on it for the next version [image: 🚀]

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#91 (comment).

[yannmh]

You make a point, the third option sounds more reasonable.
Thanks again @gnarf.

[gnarf]

This code is like really quick and dirty, but this is what I implemented in my own node.js script (if it helps at all)

Note: output contains stderr + stdout

module.exports = function(err, event) {
  var text = "%%%\nExit Code: " + event.exit + " Time: " + (event.time/1000).toFixed(3) + "s\n";

  var payload_text_limit = 4000;

  if (event.output.length > (payload_text_limit - text.length - 100) ) {
    text += 'Start:\n```\n';
    var lines = event.output.split('\n');
    while (text.length < (payload_text_limit / 3)) {
      text += lines.shift() + '\n';
    }
    text += '```\n';
    text += '...trimmed...\n';
    text += '```\n';

    var ending = '```\n';
    while ((ending.length + text.length + lines[lines.length-1].length + 1) < payload_text_limit) {
      ending = lines.pop() + '\n' + ending;
    }
    text += ending;
  } else {
    text += 'Output:\n```\n' + event.output + '\n```\n';
  }

  var properties = {
    tags: [ '#deploy:' + event.eventData.owner + '/' + event.eventData.repo, '#env:{{ deploy_env }}' ],
    host: os.hostname(),
    alert_type: event.exit ? 'error' : 'success',
    date_happened: event.start,
    source_type_name: 'deploy',
  };
  dogapi.event.create("[" + os.hostname() + "] deploy " + event.filename, text, properties);
};

I'm not proud of the readability or methods this thing uses, but hey - it works ;)