MongoDB setup

Database

                       

Overview

• MongoDB in Docker container
• Install MongoDB using Homebrew
  • Start MongoDB service
  • Verify MongoDB service
  • Stop MongoDB service
  • Re-Start MongoDB service
  • Troubleshooting
• Dependencies in Docker

This is a tutorial on how to install MongoDB on a Mac.

BTW, AWS DynamoDB provides a service for this.

MongoDB in Docker container

1. Start the Docker daemon

   sudo docker run -d -p 27017:27017 -v ~/data:/data/db mongo

2. Based on https://hub.docker.com/_/mongo/ *

   docker pull mongo:latest

Install MongoDB using Homebrew

1. Install Mongodb, on a Mac (not the latest dev release):

   brew update
   brew install mongodb

   The response (takes a long time):

   ==> Downloading https://homebrew.bintray.com/bottles/mongodb-3.2.8.el_capitan.bo
   ==> Pouring mongodb-3.2.8.el_capitan.bottle.tar.gz
   ==> Caveats
   To have launchd start mongodb now and restart at login:
     brew services start mongodb
   Or, if you don't want/need a background service you can just run:
     mongod --config /usr/local/etc/mongod.conf
   ==> Summary
   🍺  /usr/local/Cellar/mongodb/3.2.8: 17 files, 264.1M
   

   Start MongoDB service

   brew services start mongodb

   The response:

   ==> Tapping homebrew/services
   Cloning into '/usr/local/Homebrew/Library/Taps/homebrew/homebrew-services'...
   remote: Counting objects: 12, done.
   remote: Compressing objects: 100% (8/8), done.
   remote: Total 12 (delta 0), reused 7 (delta 0), pack-reused 0
   Unpacking objects: 100% (12/12), done.
   Tapped 0 formulae (40 files, 54KB)
   ==> Successfully started `mongodb` (label: homebrew.mxcl.mongodb)
   

   Verify MongoDB service

   ps -al

   Stop MongoDB service

   brew services stop mongodb

   Re-Start MongoDB service

   brew services restart mongodb

   Troubleshooting

By default docker-machine uses the virtualbox driver to create a local VM. However, Mongo uses mmap to turbo-charge access to files on disk. So tell docker to create a data volume in the container rather than in the host:

docker run –name my-local-mongo -v mongo-data:/data/db -p 27017:27017 -d mongo view raw

1. Get the IP of the VM:

   docker-machine ls

Dependencies in Docker

When an application starts, it’s a problem if its dependencies are not available.

• Load configuration settings from a JSON encoded config file
• Access a working data directory
• Establish a connection to an external mysql database
  
  

Traditionally, the approach is to ensure the database is started before starting the applications that depend on it by using Puppet, Chef, Ansible, or other configuration management tool.

“This is nothing more then a band-aid covering up the larger problem.” Kelsey Hightower says and recommends having app code handle the dependency problem. His sample in Go:

https://github.com/kelseyhightower/12-fractured-apps/blob/master/v3/main.go

• load configuration files if it exists, but fall back to sane defaults.

• Read environment variables to override configuration settings.

• Manage working directories inside the application. If they are missing create them.

• Retry the database connection, using some sort of backoff, and log errors along the way so alerts can be sent out.

  This “defensive programming” code is the “optimistic” approach. It’s usually a transient problem. At some point the database will come online.

TODO: Put startup-related code in a library for re-use.

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