hubot-heroku-keepalive

by hubot-scripts

hubot-scripts / hubot-heroku-keepalive

A hubot script that keeps the hubot Heroko web dyno alive

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hubot-heroku-keepalive

A hubot script that keeps the hubot Heroku free web dyno alive.

Note that a free Heroku dyno can only run for 18 hours/day, so it will be required to sleep for at least 6 hours. Accessing your Hubot during a sleep period will wake it, but it will return to sleep after 30 minutes.

Installation

In hubot project repository, run:

npm install hubot-heroku-keepalive --save

Then add hubot-heroku-keepalive to your

external-scripts.json
:
[
  "hubot-heroku-keepalive"
]

Configuring

hubot-heroku-keepalive is configured by four environment variables:

  • HUBOT_HEROKU_KEEPALIVE_URL
    - required, the complete URL to keepalive, including a trailing slash.
  • HUBOT_HEROKU_WAKEUP_TIME
    - optional, the time of day (HH:MM) when hubot should wake up. Default: 6:00 (6 am)
  • HUBOT_HEROKU_SLEEP_TIME
    - optional, the time of day (HH:MM) when hubot should go to sleep. Default: 22:00 (10 pm)
  • HUBOT_HEROKU_KEEPALIVE_INTERVAL
    - the interval in which to keepalive, in minutes. Default: 5

You must set

HUBOT_HEROKU_KEEPALIVE_URL
and it must include a trailing slash – otherwise the script won't run. You can find out the value for this by running
heroku apps:info
. Copy the
Web URL
and run:
heroku config:set HUBOT_HEROKU_KEEPALIVE_URL=PASTE_WEB_URL_HERE

If you want to trust a shell snippet from the Internet, here's a one-liner:

heroku config:set HUBOT_HEROKU_KEEPALIVE_URL=$(heroku apps:info -s | grep web.url | cut -d= -f2)

HUBOT_HEROKU_WAKEUP_TIME
and
HUBOT_HEROKU_SLEEP_TIME
define the waking hours - between these times the keepalive will ping your Heroku app. Outside of those times, the ping will be suppressed, allowing the dyno to shut down. These times are based on the timezone of your Heroku application which defaults to UTC. You can change this with:
heroku config:add TZ="America/New_York"

Waking Hubot Up

This script will keep the dyno alive once it is awake, but something needs to wake it up. You can use the Heroku Scheduler to wake the dyno up. Add the scheduler addon by running:

heroku addons:create scheduler:standard

The scheduler must be manually configured from the web interface, so run

heroku addons:open scheduler
and configure it to run
curl ${HUBOT_HEROKU_KEEPALIVE_URL}heroku/keepalive
at the time configured for
HUBOT_HEROKU_WAKEUP_TIME
.

Heroku Scheduler Screenshot

Note that the Scheduler's time is in UTC. If you changed your application's timezone with

TZ
, you'll need to convert that time to UTC for the wakup job. For example, if
HUBOT_HEROKU_WAKEUP_TIME
is set to
06:00
and
TZ
is set to
America/New_York
, you'll need to set the Scheduler to run at 10:00 AM UTC.

Legacy Support

Hubot has for a long time had it's own builtin way to keep its web dyno alive, but this is an extraction of that behavior.

The legacy support uses the

HEROKU_URL
environment variable instead of
HUBOT_HEROKU_KEEPALIVE_URL
, so for forward compatability, hubot-heroku-keepalive will also use HEROKU_URL if it's present, and will also disable the legacy keepalive behavior if it's present.

Development

The best way is to use

npm link
and make sure to point HUBOTHEROKUKEEPALIVE_URL at the right place:
hubot-heroku-keepalive$ npm link
hubot-heroku-keepalive$ cd /path/to/your/hubot
hubot$ npm link hubot-heroku-keepalive
hubot$ export HUBOT_HEROKU_KEEPALIVE_URL=http://localhost:8080/
hubot$ bin/hubot

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