Sync Redmine attachments to S3

I was considering a design to build Redmine on AWS, and I decided to make it redundant.

In the end, I created the configuration as shown in this figure.

Redmine itself uses ALB and Auto Scaling to determine the minimum and maximum number of EC2 units and scales based on the average CPU usage rate.
The database has a Multi-AZ configuration.

With this configuration, I was wondering what to do with the attached files.

Find plugins

There was a plugin that saved Redmine attachments to S3.
But you have to write the access key and secret key in the settings.
I would like to use IAM roles if possible, so I stopped using this plugin this time.

Sync files from each instance to S3

As a requirement, I just need to be able to view the files attached from each instance on each instance, and it doesn't need to be very real-time, so I decided to synchronize using CLI commands.

I think it would be a good idea to create an S3 bucket and periodically synchronize it bidirectionally with the /var/lib/redmine/files directory.

I regularly execute a shell file like the one above using crontab.

There are issues with files accumulating locally on EC2 and the initial synchronization of additionally launched instances taking time, so I think there is an option to use EFS, but as of January 2018, it is not usable. There are limited regions, so I think you should consider it as an option.

Thank you for reading until the end!

I wrote a book called "AWS Certification Exam Text & Question Collection AWS Certified Solution Architect - Professional Revised 2nd Edition".

I wrote a book called "AWS Certification Exam Text: AWS Certified Cloud Practitioner Revised 2nd Edition."

I wrote a book called "Pocket Study AWS Certified Developer Associate [DVA-C02 Compatible]".

I wrote a book called ``AWS Certified Solutions Architect-Associate: Getting Started with the Key Points.''

I wrote a book called ``Getting Started with Linux on AWS.''

@yamamanx

I am a Software Engineer who has been working as a development vendor for 5 years, a total of 9 years in the user company system department, and 5 years as an IT instructor.I also started working as a prototype builder.
Please feel free to ask any questions in the comments or on SNS.
I will answer to the best of my ability.

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Also, when I write a report on a study session or event, I write down what I'm interested in or what I thought after listening to it, so it's not the speaker's opinion or presentation content.