CODEWITHSUNDEEP
mongodbprovisioningchef-infra
real_ate
real_ate

Reputation: 11299

Get Chef to execute a mongodb script after mongodb has started

We're currently using chef to provision our servers and we want our recipe/cookbook to automatically add some data to the mongo database once its installed and running.

This is where we start to run into problems. We were using an execute resource to run the mongo script like this: 

execute "install-mongodb-config" do
  command "mongo #{node[:mongodb][:mongo_db_host]}/#{node[:mongodb][:mongo_db]} \"#{node[:mongodb][:mongo_add_config_script]}\""
  action :run
end

This part of the recipe always failed no matter what we tried! I won't get into the details of everything we tried here (unless i need to) but lets just say that i've exhausted all possibilities of subscribes and notifies (i think).

The problem originates from the fact that we are using the mongodb::10gen_repo to install mongodb. The recipe exits when apt-get installs the package and then chef continues on to execute more resourses.

We have tried executing the above resource directly after mongodb::10gen_repo but it doesn't seem like mongodb is available and the mongo shell cannot connect and run the script. The error we see is somewhat like this: 

MongoDB shell version: 2.0.2
Thu Sep  6 18:40:45 ReferenceError: setTimeout is not defined mongotest.js:2
failed to load: mongoAddConfig.js

Nothing we have tried has been able to get around this in a nice chef way. The thing that we resorted to was to replace the execute resource with the following: 

execute "install-mongodb-config" do
  command "sleep 60; mongo #{node[:mongodb][:mongo_db_host]}/#{node[:mongodb][:mongo_db]} \"#{node[:mongodb][:mongo_add_config_script]}\""
  action :run
end

Which just makes the command sleep for 60 seconds before the mongo script is run. I know this isn't the Right way to do this but it works for now.

Can anyone suggest the Right way to do this? I have a feeling that I will need to talk to the guys that created the mongodb chef script and request a feature!

Upvotes: 3

Views: 5516

Answers (3)

Draco Ater
Draco Ater

Reputation: 21226

First of all. Remove this "sleep 60". This can be done by chef: All resources have common attributes and "retries" and "retry_delay" are part of them. So the easiest way would be:

execute "install-mongodb-config" do
  command "mongo some_command"
  action :run
  retries 6
  retry_delay 10
end

If you have more than 2-3 places, where you have to run some command on mongo database, consider creating LWRP, similar to one created in this mongodb cookbook. (Particularly check the libraries/mongodb.rb file). You can hide the logic that waits for the server to respond there.

Upvotes: 8

cixelsyd
cixelsyd

Reputation: 936

Is it important that the same Chef run that installs the software also injects the initial configuration? The 'chefly' method to constructing cookbooks and recipes is to guard against idempotency in order to ensure that they can be run over and over again without producing unintended results.

In this particular case, I would limit the first recipe to only just installing and starting up mongodb. This recipe would do nothing if it saw that mongodb was already running on the host. Then, I'd have another recipe that would run only if it saw that mongo had been setup and was running. It would query the mongodb to see if the initial configuration had been done. If so, it would simply return. If not, it would run your configuration routine.

In this way, these recipes could run all the time, anytime, on your machine. Even if someone uninstalled mongodb, chef would get around to ensuring that it was set back up again and pristine.

Upvotes: 1

ChadsworthIII
ChadsworthIII

Reputation: 106

So, I don't know much at all about chef. But your problem seems to be that you try to immediately connect after bringing the server up.

Server's are not immediately available when you bring them up since there is a bit of overhead that goes into electing a primary, getting all the server status's etc.

You can recreate this without chef by trying to bring up a replica set and immediately trying to connect to it in a simple script. So it's not chef specific.

Not sure if there is a way around the server startup lag since bringing up a primary is expected to be a relatively infrequent occurrence compared to just adding nodes to a set.

The only potential solution I see that is cleaner is adding a longer Timeout for the connection to be formed in the configuration. You can find how to do this in the mongodb documentation here: http://www.mongodb.org/display/DOCS/Connections

The flag of interest for you is likely connectTimeoutMS

Upvotes: 0

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