MySQL S3 Download

A small MySQL UDF library for downloading files from an AWS S3 bucket written in Golang.

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Usage

Know what you're doing! I'm sure this is wrong for a multitude reasons, but I'm personally using it for debug reasons, and because sometimes it's quicker to throw a query into Workbench then it is to write a script to view a file on S3, so, here it is.

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s3_download

Downloads a file from AWS S3 and returns the contents. Returns NULL if any of the params are NULL, or if the file doesn't exist, or there is some other error while downloading.

`s3_download` ( `region` , `bucket` , `key` )

• `region`
  • The AWS region that the bucket is in.
    • Example: us-east-1
• `bucket`
  • The AWS S3 bucket that the file is in.
• `key`
  • The key of the file you wish to download without the leading slash. Example: ""
    • Example: path/to/file.csv

Examples

select`s3_download`('us-east-1','bucket.of.brian','path/to/file.csv');

--'Id,Name,Age
-- 1,Ahmad,21
-- 2,Ali,50'

select`s3_download`('us-east-1','bucket.of.brian','path/that/is/bad'); -- NULL
select`s3_download`('us-east-1',null,'path/to/file.csv'); -- NULL

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Downloading Errors

As you can see in the examples and the description above, the functions returns NULL if there is an error while downloading. If you do want to see the actual error messages, they will appear in the MySQL error log file like so:

tail -f /var/log/mysql/error.log # or wherever your MySQL error log is
s3-download: 2020/09/24 18:11:10.040207 /home/brian/go/src/github.com/StirlingMarketingGroup/mysql-s3-download/main.go:79: failed to download file from S3: NoSuchKey: The specified key does not exist.
        status code: 404, request id: ..., host id: ...

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Dependencies

You will need Golang, which you can get from here https://golang.org/doc/install. You will also need the MySQL dev library.

Debian / Ubuntu

sudo apt update
sudo apt install libmysqlclient-dev

Configuring

Similar to other tools that connect to AWS, your AWS credentials must be set as environment variables. This is trivial if you're using something like Docker for running your database(s), but you can also set them on bare metal Ubuntu, for example, boxes by adding them to your /etc/environment file, or however your OS's environment variables are defined.

sudo nano /etc/environment

# Add these to the bottom

AWS_ACCESS_KEY_ID=Your key...
AWS_SECRET_ACCESS_KEY=Your secret...

Installing

You can find your MySQL plugin directory by running this MySQL query

select @@plugin_dir;

then replace /usr/lib/mysql/plugin below with your MySQL plugin directory.

cd ~ # or wherever you store your git projects
git clone https://github.com/StirlingMarketingGroup/mysql-s3-download.git
cd mysql-s3-download
go get -d ./...
go build -buildmode=c-shared -o s3_download.so
sudo cp s3_download.so /usr/lib/mysql/plugin/ # replace plugin dir here if needed

Enable the functions in MySQL by running this MySQL query

create function`s3_download`returns string soname's3_download.so';