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Differential deploy to Amazon S3 from BitBucket

gmoretti profile image giuseppe ・6 min read

This is my first post on, very glad to participate and happy to pump up those writing skills.

Under the idea to automate the deployments of our static files and as a step toward a CI/CD environment, and taking adventage from the fact that we recently move all the static files to AWS S3 buckets, I've decided to give it a try automating our process.

Current state

Our deployment process (the integration one) has two big elements to deploy: A Salesforce package. And a folder with all the static files that the Salesforce package uses, including front end code.

When this Salesforce package is created the repository is tagged with a TEST_X name.

Currently the process to deploy statics goes like this:

  1. Go to Source Tree.
  2. Check the files that changed between current and the last TAG.
  3. Copy these files into AWS S3
  4. Invalidate Cloudfire cache (Amazon's CDN... sort of)

Once this first big deploy has been done it can happen also that minor changes that only require static deployment get deployed individually. Without the need of generating another package.

The new apporach

Use Bitbucket pipelines to execute a script with what we just described.

There is already a very good pipeline for AWS S3 ready to use. The only drawback is that the sync commando used to copy the files to S3 uses a combination of timestamp and size of the files to decide wether do the upload or not. Since in BitBucket the pipe executes from a docker container the files that get clones from GIT always have a more recend timestamp than the ones on S3, meaning all the files get copied no matter what.

The only new thing the script will do will be:

  1. Use GIT diff to get the changed files (if we are in a TAG or not changes the behaviour)
  2. AWS CLI to send the specific files
  3. AWS CLI to invalidate cache programatically

Simple Bitbucket Pipe

The first step is to create a pipe from where we will execute the script.
I think the official documentation does quite a good job on this matter. Remember we will use the Simple Pipe to keep files and code at a minimum.

The only part that I missed from the bitbucket docs was that it makes you think it's not possible to access repository defined variables from the simple pipe. This is half true since you can actually pass them when using the pipe in your project's bitbucket-pipelines.yml file.


The instructions leave you with a three file project. Let's start with the Dockerfile.

FROM atlassian/pipelines-awscli:1.16.185
RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*

The only difference from the provided is the first line

FROM atlassian/pipelines-awscli:1.16.185

This provides us with the AWS CLI tools pre installed, so we don't have to do it on building time.

Pipe Script

Next, we have the script we will use as a pipe, and it would be the one that contains the GIT commands, the deployment and the cache invalidation.
I based this script heavily in what was exposed in this article. Let's have a look.

#!/usr/bin/env bash
#TODO: Apply colors and errors with
set -ex

# mandatory parameters
# path variables should not contain slashes
S3_BUCKET=${S3_BUCKET:?'S3_BUCKET variable missing.'}
LOCAL_PATH=${LOCAL_PATH:?'LOCAL_PATH variable missing.'}
TAG_REGEX=${TAG_REGEX:?'TAG_REGEX variable missing.'}

echo "Starting deployment..."
echo "S3_BUCKET is: ${S3_BUCKET}"

# This will give us the last two tags created that comply with the TAG_REGEX parameter
for i in $( git tag -l --sort=refname "${TAG_REGEX}" | tail -2 ); do
    TAGS+=( "$i" )

echo "Checking difference between tags:"
echo "${TAGS[0]}"
echo "${TAGS[1]}"

# We will get the list of files that changed between those two tags but keep only the ones that
# begin with the path we want to deploy
for i in $( git diff ${TAGS[0]} ${TAGS[1]} --name-only | sed -n "s|${LOCAL_PATH}/||p" ); do
    FILES+=( "$i" )
echo "Files to be deployed..."
printf '%s\n' "${FILES[@]}"

# Construct the parameters to the AWS CLI for the files to includes
for i in "${FILES[@]}"; do
echo "${CMDS[@]}"

# Exclude ALL diles and only includes the previously defined.
# Remove dryrun to deploy to aws s3
# Remember this command won't show any output if the file in the bucket is MORE RECENT than the one in local
echo "${CMDS[@]}" | xargs aws s3 sync ./${LOCAL_PATH}/ s3://${S3_BUCKET}/ --dryrun --delete --exclude "*"

aws cloudfront create-invalidation --distribution-id ${CLOUDFRONT_DISTRIBUTION_ID} --paths /folderToInvalidate/*

The paremeters section at the beggining it's more as a reminder of what are we going to have during the script, these variables will come from the configuration when using the pipe. It is worth remind you that all the paths should not contain slashes, this is critical
since AWS S3 doesn't allow dopuble slashes.

We list the files that have change, exclude all files from the ´´aws sync´´ command amd include only the ones that have changed.
We finally invalidate cache of directory on cloudfire to be able to see the changes if needed.

Last but not least, before pushing this file to the repo execute a

chmod -x

To have execution permission once in docker.


This file configures the upload of your pipe to dockerhub, just don't forget to have available in your repo
the docker hub credential variables.

The project with the static files

Now we configure the pipeline file for our project (bitbucket repo) to use the new pipe and pass the necessary variables.
My bitbucket-pipelines.yml file looks like this:

# This is a sample build configuration for Other.
# Check our guides at for more examples.
# Only use spaces to indent your .yml configuration.
# -----
# You can specify a custom docker image from Docker Hub as your build environment.
image: atlassian/default-image:2

      - step:
            - pipe: docker://gmoretti/aws-deploy-diff-last-tag-simple-pipe:latest
                S3_BUCKET: 'aws-static-deploy-test'
                LOCAL_PATH: 'static'
                TAG_REGEX: 'TEST_*'

Let's go line by line, first thing we declare this as a custom step, so to use it we need to go to bitbucket branch and manually click on it, next line is the name of the step taht will appear in the list of things that can be executed.


Next, the url to your pipe in dockerhub.

            - pipe: docker://gmoretti/aws-deploy-diff-last-tag-simple-pipe:latest

Now, we have our AWS credentials, you could easily hardcode them here, but they are better as repository variables, specially now that bitbucket lets you have different ones per environment.


Next, the target bucket without the protocol S3:// nor any slash at the end. You can add the target path to the very specific folder you want the files on.

                S3_BUCKET: 'aws-static-deploy-test'

Since we are in the root of the project we put the path to the directory we want to deploy. Again, no slashes at the start or end.

                LOCAL_PATH: 'static'

The last variable will help us match with the TAGS we want to compare, so they need to be somehow numerically secuential.

                TAG_REGEX: 'TEST_*'

This will match all tags like TEST_1, TEST_3, TEST_6, etc.


Now, we only need to push all the changes go to branches in bitbucket and execute the pipe.

Final thoughts

Alotought to solve this specific case, this pipe would work great, the thing is that there are several other cases that have not been covered, like, deploying files not covered by a tag or commiting files between several tags. Althought all these things can be done extending the pipe script, the truth is that just tagging and deploying all the static files will eliminate the whole problem and will leave as using the bitbucket AWS S3 mantained pipe.

That's what I would take home today.


If you have any thoughts feel free to contact me, thank you!

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