In this chapter, we will implement the ability to download and upload files in the application. In addition, we will discuss some aspects of working with files in Kubernetes and provide a practical example of using S3-compatible storage.

The application described in this chapter is not intended for use in production environments as-is. Note that successful completion of this entire guide is required to create a production-ready application.

Preparing the environment

Prepare the environment using the instructions provided in the “Preparing the environment” chapter (if you have not done this already).

Please, refer to these helpful resources if the environment has stopped working or instructions in this chapter don’t work:

Is Docker running?

Let’s launch Docker Desktop. It takes some time for this application to start Docker. If there are no errors during the startup process, check that Docker is running and is properly configured:

docker run hello-world

You will see the following output if the command completes successfully:

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
b8dfde127a29: Pull complete
Digest: sha256:9f6ad537c5132bcce57f7a0a20e317228d382c3cd61edae14650eec68b2b345c
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

Should you have any problems, please refer to the Docker documentation.

Let’s launch the Docker Desktop application. It takes some time for the application to start Docker. If there are no errors during the startup process, then check that Docker is running and is properly configured:

docker run hello-world

You will see the following output if the command completes successfully:

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
b8dfde127a29: Pull complete
Digest: sha256:9f6ad537c5132bcce57f7a0a20e317228d382c3cd61edae14650eec68b2b345c
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

Should you have any problems, please refer to the Docker documentation.

Start Docker:

sudo systemctl restart docker

Make sure that Docker is running:

sudo systemctl status docker

If the Docker start is successful, you will see the following output:

● docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2021-06-24 13:05:17 MSK; 13s ago
TriggeredBy: ● docker.socket
       Docs: https://docs.docker.com
   Main PID: 2013888 (dockerd)
      Tasks: 36
     Memory: 100.3M
     CGroup: /system.slice/docker.service
             └─2013888 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

dockerd[2013888]: time="2021-06-24T13:05:16.936197880+03:00" level=warning msg="Your kernel does not support CPU realtime scheduler"
dockerd[2013888]: time="2021-06-24T13:05:16.936219851+03:00" level=warning msg="Your kernel does not support cgroup blkio weight"
dockerd[2013888]: time="2021-06-24T13:05:16.936224976+03:00" level=warning msg="Your kernel does not support cgroup blkio weight_device"
dockerd[2013888]: time="2021-06-24T13:05:16.936311001+03:00" level=info msg="Loading containers: start."
dockerd[2013888]: time="2021-06-24T13:05:17.119938367+03:00" level=info msg="Loading containers: done."
dockerd[2013888]: time="2021-06-24T13:05:17.134054120+03:00" level=info msg="Daemon has completed initialization"
systemd[1]: Started Docker Application Container Engine.
dockerd[2013888]: time="2021-06-24T13:05:17.148493957+03:00" level=info msg="API listen on /run/docker.sock"

Now let’s check if Docker is available and its configuration is correct:

docker run hello-world

You will see the following output if the command completes successfully:

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
b8dfde127a29: Pull complete
Digest: sha256:9f6ad537c5132bcce57f7a0a20e317228d382c3cd61edae14650eec68b2b345c
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

Should you have any problems, please refer to the Docker documentation.

Have you restarted the computer after setting up the environment?

Let’s start the minikube cluster we have already configured in the “Preparing the environment” chapter:

minikube start

Set the default Namespace so that you don’t have to specify it every time you invoke kubectl:

kubectl config set-context minikube --namespace=werf-guide-app

You will see the following output if the command completes successfully:

😄  minikube v1.20.0 on Ubuntu 20.04
✨  Using the docker driver based on existing profile
👍  Starting control plane node minikube in cluster minikube
🚜  Pulling base image ...
🎉  minikube 1.21.0 is available! Download it: https://github.com/kubernetes/minikube/releases/tag/v1.21.0
💡  To disable this notice, run: 'minikube config set WantUpdateNotification false'

🔄  Restarting existing docker container for "minikube" ...
🐳  Preparing Kubernetes v1.20.2 on Docker 20.10.6 ...
🔎  Verifying Kubernetes components...
    ▪ Using image gcr.io/google_containers/kube-registry-proxy:0.4
    ▪ Using image k8s.gcr.io/ingress-nginx/controller:v0.44.0
    ▪ Using image registry:2.7.1
    ▪ Using image docker.io/jettech/kube-webhook-certgen:v1.5.1
    ▪ Using image docker.io/jettech/kube-webhook-certgen:v1.5.1
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
🔎  Verifying registry addon...
🔎  Verifying ingress addon...
🌟  Enabled addons: storage-provisioner, registry, default-storageclass, ingress
🏄  Done! kubectl is now configured to use "minikube" cluster and "werf-guide-app" namespace by default

Make sure that the command output contains the following line:

Restarting existing docker container for "minikube"

Its absence means that a new minikube cluster was created instead of using the old one. In this case, repeat all the steps required to install the environment using minikube.

Now run the command in the background PowerShell terminal (do not close its window):

minikube tunnel --cleanup=true

Let’s start the minikube cluster we have already configured in the “Preparing the environment” chapter:

minikube start --namespace werf-guide-app

Set the default Namespace so that you don’t have to specify it every time you invoke kubectl:

kubectl config set-context minikube --namespace=werf-guide-app

You will see the following output if the command completes successfully:

😄  minikube v1.20.0 on Ubuntu 20.04
✨  Using the docker driver based on existing profile
👍  Starting control plane node minikube in cluster minikube
🚜  Pulling base image ...
🎉  minikube 1.21.0 is available! Download it: https://github.com/kubernetes/minikube/releases/tag/v1.21.0
💡  To disable this notice, run: 'minikube config set WantUpdateNotification false'

🔄  Restarting existing docker container for "minikube" ...
🐳  Preparing Kubernetes v1.20.2 on Docker 20.10.6 ...
🔎  Verifying Kubernetes components...
    ▪ Using image gcr.io/google_containers/kube-registry-proxy:0.4
    ▪ Using image k8s.gcr.io/ingress-nginx/controller:v0.44.0
    ▪ Using image registry:2.7.1
    ▪ Using image docker.io/jettech/kube-webhook-certgen:v1.5.1
    ▪ Using image docker.io/jettech/kube-webhook-certgen:v1.5.1
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
🔎  Verifying registry addon...
🔎  Verifying ingress addon...
🌟  Enabled addons: storage-provisioner, registry, default-storageclass, ingress
🏄  Done! kubectl is now configured to use "minikube" cluster and "werf-guide-app" namespace by default

Make sure that the command output contains the following line:

Restarting existing docker container for "minikube"

Its absence means that a new minikube cluster was created instead of using the old one. In this case, repeat all the steps required to install the environment from scratch using minikube.

Did you accidentally delete the application's Namespace?

If you have inadvertently deleted Namespace of the application, you must run the following commands to proceed with the guide:

kubectl create namespace werf-guide-app
kubectl create secret docker-registry registrysecret \
  --docker-server='https://index.docker.io/v1/' \
  --docker-username='<Docker Hub username>' \
  --docker-password='<Docker Hub password>'

You will see the following output if the command completes successfully:

namespace/werf-guide-app created
secret/registrysecret created
Nothing helps; the environment or instructions keep failing.

If nothing worked, repeat all the steps described in the “Preparing the environment” chapter and create a new environment from scratch. If creating an environment from scratch did not help either, please, tell us about your problem in our Telegram chat or create an issue on GitHub. We will be happy to help you!

Preparing the repository

Update the existing repository containing the application:

Run the following commands in PowerShell:

cd ~/werf-guide/app

# To see what changes we will make later in this chapter, let's replace all the application files
# in the repository with new, modified files containing the changes described below.
git rm -r .
cp -Recurse -Force ~/werf-guide/guides/examples/rails/050_s3/* .
git add .
git commit -m WIP
What changes we will make
# Enter the command below to show the files we are going to change.
git show --stat
# Enter the command below to show the changes that will be made.
git show

Run the following commands in Bash:

cd ~/werf-guide/app

# To see what changes we will make later in this chapter, let's replace all the application files
# in the repository with new, modified files containing the changes described below.
git rm -r .
cp -rf ~/werf-guide/guides/examples/rails/050_s3/. .
git add .
git commit -m WIP
What changes we will make
# Enter the command below to show files we are going to change.
git show --stat
# Enter the command below to show the changes that will be made.
git show

Doesn’t work? Try the instructions on the “I am just starting from this chapter” tab above.

Prepare a new repository with the application:

Run the following commands in PowerShell:

# Clone the example repository to ~/werf-guide/guides (if you have not cloned it yet).
if (-not (Test-Path ~/werf-guide/guides)) {
  git clone https://github.com/werf/werf-guides $env:HOMEPATH/werf-guide/guides
}

# Copy the (unchanged) application files to ~/werf-guide/app.
rm -Recurse -Force ~/werf-guide/app
cp -Recurse -Force ~/werf-guide/guides/examples/rails/040_db ~/werf-guide/app

# Make the ~/werf-guide/app directory a git repository.
cd ~/werf-guide/app
git init
git add .
git commit -m initial

# To see what changes we will make later in this chapter, let's replace all the application files
# in the repository with new, modified files containing the changes described below.
git rm -r .
cp -Recurse -Force ~/werf-guide/guides/examples/rails/050_s3/* .
git add .
git commit -m WIP
What changes we will make
# Enter the command below to show the files we are going to change.
git show --stat
# Enter the command below to show the changes that will be made.
git show

Run the following commands in Bash:

# Clone the example repository to ~/werf-guide/guides (if you have not cloned it yet).
test -e ~/werf-guide/guides || git clone https://github.com/werf/werf-guides ~/werf-guide/guides

# Copy the (unchanged) application files to ~/werf-guide/app.
rm -rf ~/werf-guide/app
cp -rf ~/werf-guide/guides/examples/rails/040_db ~/werf-guide/app

# Make the ~/werf-guide/app directory a git repository.
cd ~/werf-guide/app
git init
git add .
git commit -m initial

# To see what changes we will make later in this chapter, let's replace all the application files
# in the repository with new, modified files containing the changes described below.
git rm -r .
cp -rf ~/werf-guide/guides/examples/rails/050_s3/. .
git add .
git commit -m WIP
What changes we will make
# Enter the command below to show files we are going to change.
git show --stat
# Enter the command below to show the changes that will be made.
git show

Storing files

Containers running in Kubernetes are often created and deleted automatically, e.g., because of Deployment updates. This means that application files cannot be stored on the container file system since those files will be:

  • available to a single container/application replica rather than all of them;
  • deleted when the container is killed.

Thus, it makes sense to store in the containers only the data you can afford to lose.

By the way, you can set the container file system to read-only. This will improve security and prevent the application from storing data locally.

But what if you need to keep some data? You can use standalone databases for that. For example, NoSQL databases such as object storages are often used for storing regular files. Object stores that provide an Amazon S3-compatible API are especially popular.

Below, we will show you how to store files in S3-compatible storage instead of a local file system. This way, your application can remain stateless and avoid some issues when working in Kubernetes.

Enabling Active Storage

We have to enable the Active Storage component to use the object storage.

Thus, we introduced a basic Active Storage configuration in our application using a new skeleton Rails app generated by the following command (note that the --skip-active-storage flag was removed):

rails new --database mysql \
  --skip-action-cable --skip-action-mailbox --skip-action-mailer --skip-action-text \
  --skip-active-job \
  --skip-javascript --skip-jbuilder --skip-turbolinks \
  --skip-keeps --skip-listen --skip-bootsnap --skip-spring --skip-sprockets \
  --skip-test --skip-system-test .

Here is the list of changes made to our application:

  1. Adding the aws-sdk-s3 gem to Gemfile.
  2. Adding the rails-activestorage package to package.json.
  3. Enabling active_storage/engine in config/application.rb and initializing Active Storage in packs/application.js.
  4. Generating a migration that creates tables required for Active Storage.
  5. Creating the config/storage.yml configuration file.

Adding /upload and /download endpoints to the application

Let’s add two new endpoints, /upload (to upload a file to the S3-compatible object storage) and /download (to download a file from the S3-compatible object storage), to see how uploading and downloading works.

Let’s add a new controller and model:

class S3FileController < ActionController::API
  def download
    begin
      file = S3File.find(0)
    rescue ActiveRecord::RecordNotFound => e
      render plain: "You haven't uploaded anything yet.\n" and return
    end

    send_data file.file.download, filename: file.file.blob.filename.to_s, type: file.file.blob.content_type, disposition: "inline"
  end

  def upload
    unless params.dig(:file).present?
      render plain: "You didn't pass the file to upload :(\n" and return
    end

    begin
      file = S3File.find(0)
    rescue ActiveRecord::RecordNotFound => e
      file = S3File.new
    end
    file.update(id: 0)
    file.file.attach(params[:file])
    file.save()

    render plain: "File uploaded.\n"
  end
end
class S3FileController < ActionController::API def download begin file = S3File.find(0) rescue ActiveRecord::RecordNotFound => e render plain: "You haven't uploaded anything yet.\n" and return end send_data file.file.download, filename: file.file.blob.filename.to_s, type: file.file.blob.content_type, disposition: "inline" end def upload unless params.dig(:file).present? render plain: "You didn't pass the file to upload :(\n" and return end begin file = S3File.find(0) rescue ActiveRecord::RecordNotFound => e file = S3File.new end file.update(id: 0) file.file.attach(params[:file]) file.save() render plain: "File uploaded.\n" end end
class S3File < ActiveRecord::Base
  has_one_attached :file
end
class S3File < ActiveRecord::Base has_one_attached :file end

Now it is time to add new paths to the routes:

...
get '/download', to: 's3_file#download'
post '/upload', to: 's3_file#upload'
... get '/download', to: 's3_file#download' post '/upload', to: 's3_file#upload'

Don’t forget about the migration to create tables:

class CreateS3Files < ActiveRecord::Migration[6.1]
  def change
    create_table :s3_files do |f|
    end
  end
end
class CreateS3Files < ActiveRecord::Migration[6.1] def change create_table :s3_files do |f| end end end

Now let’s generate and save new db/schema.rb.

New endpoints, /upload and /download, have been added. Next, we need to configure them to work with the storage.

Deploying and configuring MinIO

For illustrative purposes, we will use the MinIO S3-compatible object storage. However, you can use any other S3-compatible storage (such as Amazon S3) instead.

If the different type of S3 storage is used, you do not need to create MinIO’s StatefulSet and Job as described below. However, all further steps remain unchanged.

Let’s add a StatefulSet for MinIO:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: minio
spec:
  serviceName: minio
  selector:
    matchLabels:
      app: minio
  template:
    metadata:
      labels:
        app: minio
    spec:
      containers:
      - name: minio
        image: minio/minio
        args: ["server", "/data", "--console-address", ":9001"]
        ports:
        - containerPort: 9000
          name: minio
        - containerPort: 9001
          name: console
        volumeMounts:
        - name: minio-data
          mountPath: /data
  volumeClaimTemplates:
  - metadata:
      name: minio-data
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 100Mi

---
apiVersion: v1
kind: Service
metadata:
  name: minio
spec:
  selector:
    app: minio
  ports:
  - port: 9000
    name: minio
  - port: 9001
    name: console
apiVersion: apps/v1 kind: StatefulSet metadata: name: minio spec: serviceName: minio selector: matchLabels: app: minio template: metadata: labels: app: minio spec: containers: - name: minio image: minio/minio args: ["server", "/data", "--console-address", ":9001"] ports: - containerPort: 9000 name: minio - containerPort: 9001 name: console volumeMounts: - name: minio-data mountPath: /data volumeClaimTemplates: - metadata: name: minio-data spec: accessModes: ["ReadWriteOnce"] resources: requests: storage: 100Mi --- apiVersion: v1 kind: Service metadata: name: minio spec: selector: app: minio ports: - port: 9000 name: minio - port: 9001 name: console

The next step is to create a Job for setting up MinIO:

apiVersion: batch/v1
kind: Job
metadata:
  name: "setup-minio-rev{{ .Release.Revision }}"
spec:
  backoffLimit: 0
  template:
    spec:
      restartPolicy: Never
      containers:
      - name: setup-minio
        image: minio/mc
        command:
        - sh
        - -euc
        - |
          is_minio_available() {
            tries=$1
            i=0
            while [ $i -lt $tries ]; do
              curl -sSL http://minio:9000/minio/health/live || return 1
              i=$((i+1))
              sleep 1
            done
          }

          # Waiting for MinIO to become available.
          until is_minio_available 10; do
            sleep 1
          done

          # Configuring access to the MinIO instance.
          mc alias set minio http://minio:9000 minioadmin minioadmin

          # Creating a bucket for the application.
          mc mb --ignore-existing minio/werf-guide-app
apiVersion: batch/v1 kind: Job metadata: name: "setup-minio-rev{{ .Release.Revision }}" spec: backoffLimit: 0 template: spec: restartPolicy: Never containers: - name: setup-minio image: minio/mc command: - sh - -euc - | is_minio_available() { tries=$1 i=0 while [ $i -lt $tries ]; do curl -sSL http://minio:9000/minio/health/live || return 1 i=$((i+1)) sleep 1 done } # Waiting for MinIO to become available. until is_minio_available 10; do sleep 1 done # Configuring access to the MinIO instance. mc alias set minio http://minio:9000 minioadmin minioadmin # Creating a bucket for the application. mc mb --ignore-existing minio/werf-guide-app

Add the configuration for connecting to MinIO:

minio:
  service: S3
  endpoint: http://minio:9000
  region: us-east-1
  bucket: werf-guide-app
  access_key_id: minioadmin
  secret_access_key: minioadmin
  force_path_style: true
minio: service: S3 endpoint: http://minio:9000 region: us-east-1 bucket: werf-guide-app access_key_id: minioadmin secret_access_key: minioadmin force_path_style: true

Activate the configured MinIO storage to store files:

...
config.active_storage.service = :minio
... config.active_storage.service = :minio

MinIO is now ready to be deployed while our application is configured to store files with it.

Testing the storage

First, let’s deploy our application:

werf converge --repo <DOCKER HUB USERNAME>/werf-guide-app

You should see the following output:

...
┌ ⛵ image backend
│ ┌ Building stage backend/dockerfile
│ │ backend/dockerfile  Sending build context to Docker daemon  338.4kB
│ │ backend/dockerfile  Step 1/25 : FROM ruby:2.7 as base
│ │ backend/dockerfile   ---> 1faa5f2f8ca3
...
│ │ backend/dockerfile  Step 25/25 : LABEL werf-version=v1.2.13+fix12
│ │ backend/dockerfile   ---> Running in 14e4091f77b4
│ │ backend/dockerfile  Removing intermediate container 14e4091f77b4
│ │ backend/dockerfile   ---> a13f82df04f3
│ │ backend/dockerfile  Successfully built a13f82df04f3
│ │ backend/dockerfile  Successfully tagged 5ee7a784-4b47-402c-8fe1-b15af1418df0:latest
│ │ ┌ Store stage into .../werf-guide-app
│ │ └ Store stage into .../werf-guide-app (13.79 seconds)
│ ├ Info
│ │      name: .../werf-guide-app:2fafb795aa5ea01de13a6095eeca262552b79dddfedc887b1781bc5f-1630413036132
│ │        id: a13f82df04f3
│ │   created: 2021-08-31 15:30:35 +0300 MSK
│ │      size: 366.3 MiB
│ └ Building stage backend/dockerfile (23.83 seconds)
└ ⛵ image backend (30.97 seconds)

┌ ⛵ image frontend
│ ┌ Building stage frontend/dockerfile
│ │ frontend/dockerfile  Sending build context to Docker daemon  338.4kB
│ │ frontend/dockerfile  Step 1/29 : FROM ruby:2.7 as base
│ │ frontend/dockerfile   ---> 1faa5f2f8ca3
...
│ │ frontend/dockerfile  Step 29/29 : LABEL werf-version=v1.2.13+fix12
│ │ frontend/dockerfile   ---> Running in 0eba0fb1b573
│ │ frontend/dockerfile  Removing intermediate container 0eba0fb1b573
│ │ frontend/dockerfile   ---> b9bbdb91f081
│ │ frontend/dockerfile  Successfully built b9bbdb91f081
│ │ frontend/dockerfile  Successfully tagged c5c02694-3157-4e24-a6f5-e3efddf1fcf5:latest
│ │ ┌ Store stage into .../werf-guide-app
│ │ └ Store stage into .../werf-guide-app (14.95 seconds)
│ ├ Info
│ │      name: .../werf-guide-app:8dd338dab9cf7e58c1aafbd3c99589c68517812054d38d5eca46b69e-1630413035974
│ │        id: b9bbdb91f081
│ │   created: 2021-08-31 15:30:35 +0300 MSK
│ │      size: 9.5 MiB
│ └ Building stage frontend/dockerfile (24.97 seconds)
└ ⛵ image frontend (32.04 seconds)

Release "werf-guide-app" does not exist. Installing it now.

┌ Waiting for release resources to become ready
│ ┌ Status progress
│ │ DEPLOYMENT      REPLICAS  AVAILABLE  UP-TO-DATE
│ │ werf-guide-app  1/1       0          1
│ │ │    POD                         READY  RESTARTS  STATUS    ---
│ │ └──  guide-app-6b89879785-pklns  0/2    0         Init:0/1  Waiting  for:  available  0->1
│ │ STATEFULSET  REPLICAS  READY  UP-TO-DATE
│ │ minio        1/1       0      1
│ │ │    POD  READY  RESTARTS  STATUS             ---
│ │ └──  0    0/1    0         ContainerCreating  Waiting  for:  ready  0->1
│ │ mysql        1/1       1      1
│ │ JOB                        ACTIVE  DURATION  SUCCEEDED/FAILED
│ │ setup-and-migrate-db-rev1  1       3s        0/0
│ │ │    POD                        READY  RESTARTS  STATUS             ---
│ │ └──  and-migrate-db-rev1-jhlh8  0/1    0         ContainerCreating  Waiting  for:  pods  should  be  terminated,  succeeded  0->1
│ │ setup-minio-rev1           1       3s        0/0
│ │ │    POD               READY  RESTARTS  STATUS             ---
│ │ └──  minio-rev1-v72nq  0/1    0         ContainerCreating  Waiting  for:  pods  should  be  terminated,  succeeded  0->1
│ └ Status progress
...
│ ┌ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│ │ rails aborted!
│ │ ActiveRecord::ConnectionNotEstablished: Cant connect to MySQL server on 'mysql' (115)
│ │
│ │ Caused by:
│ │ Mysql2::Error::ConnectionError: Cant connect to MySQL server on 'mysql' (115)
│ │
│ │ Tasks: TOP => db:migrate:status
│ │ (See full trace by running task with --trace)
│ └ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│
│ ┌ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
│ │ mysqladmin: connect to server at 'mysql' failed
│ │ error: 'Cant connect to MySQL server on 'mysql' (115)'
│ │ Check that mysqld is running and that the socket: '/var/run/mysqld/mysqld.sock' exists!
│ └ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
|
│ ┌ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
│ │ mysqladmin: connect to server at 'mysql' failed
│ │ error: 'Access denied for user 'root'@'172.17.0.1' (using password: YES)'
│ └ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
│
│ ┌ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│ │ rails aborted!
│ │ ActiveRecord::NoDatabaseError: Unknown database 'werf-guide-app'
│ │
│ │ Caused by:
│ │ Mysql2::Error: Unknown database 'werf-guide-app'
│ │
│ │ Tasks: TOP => db:migrate:status
│ │ (See full trace by running task with --trace)
│ └ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│
│ ┌ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
│ │ Created database 'werf-guide-app'
│ └ job/setup-and-migrate-db-rev1 po/setup-and-migrate-db-rev1-jhlh8 container/setup-and-migrate-db logs
│
│ ┌ job/setup-minio-rev1 po/setup-minio-rev1-v72nq container/setup-minio logs
│ │ Added "minio" successfully.
│ │ Bucket created successfully "minio/werf-guide-app".
│ └ job/setup-minio-rev1 po/setup-minio-rev1-v72nq container/setup-minio logs
...
│ ┌ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│ │
│ │ database: werf-guide-app
│ │
│ │  Status   Migration ID    Migration Name
│ │ --------------------------------------------------
│ │    up     20210817162438  Create talkers
│ │    up     20210817164348  Add name to talkers
│ │   down    20210830170827  Create active storage tablesactive storage
│ │   down    20210830171006  Create s3 files
│ │
│ └ deploy/werf-guide-app po/werf-guide-app-6b89879785-pklns container/wait-db-readiness logs
│
│ ┌ Status                     progress
│ │ DEPLOYMENT      REPLICAS  AVAILABLE  UP-TO-DATE
│ │ werf-guide-app  1/1       0->1       1
│ │ │    POD                         READY  RESTARTS  STATUS
│ │ └──  guide-app-6b89879785-pklns  2/2    0         PodInitializing  ->  Running
│ │ STATEFULSET  REPLICAS  READY  UP-TO-DATE
│ │ minio        1/1       1      1
│ │ │    POD  READY  RESTARTS  STATUS
│ │ └──  0    1/1    0         Running
│ │ mysql        1/1       1      1
│ │ JOB                        ACTIVE  DURATION  SUCCEEDED/FAILED
│ │ setup-and-migrate-db-rev1  0       24s       1/0
│ │ │    POD                        READY  RESTARTS  STATUS
│ │ └──  and-migrate-db-rev1-jhlh8  0/1    0         Completed
│ │ setup-minio-rev1           0       25s       1/0
│ │ │    POD               READY  RESTARTS  STATUS
│ │ └──  minio-rev1-v72nq  0/1    0         Completed
│ └ Status                     progress
└ Waiting for release resources to become ready (30.31 seconds)

NAME: werf-guide-app
LAST DEPLOYED: Tue Aug 31 15:30:55 2021
NAMESPACE: werf-guide-app
STATUS: deployed
REVISION: 1
TEST SUITE: None
Running time 65.26 seconds

Now let’s access the /download endpoint to get the file from S3:

curl http://werf-guide-app/download

Since we haven’t uploaded any files yet, we’ll get this:

You haven't uploaded anything yet.

Now let’s create a new file and upload it to the S3 storage:

echo "This is file content." > file.txt
curl -F "file=@file.txt" http://werf-guide-app/upload
"This is file content." | Out-File -Encoding ascii -FilePath file.txt
curl.exe -F "file=@file.txt" http://werf-guide-app/upload

The expected output indicates that the file has been successfully added to the storage:

File uploaded.

Let’s try to pull the file from the storage again:

curl http://werf-guide-app/download

You should see the file content:

This is file content.

Let’s make sure that the file gets saved directly to the storage and pulled from it. To do this, run the container having the mc tool to interact with MinIO:

kubectl run mc --image=minio/mc --rm -it --command -- bash

Now, execute the following commands in the container’s shell:

# Connect to MinIO
mc alias set minio http://minio:9000 minioadmin minioadmin
# Get the content of file stored in S3
mc cat "minio/werf-guide-app/$(mc ls minio/werf-guide-app | awk 'NR==1 {print $5}')"

The expected outcome:

This is file content.

In this chapter, we learned how to store files in the S3-compatible object storage instead of the container file system. With this approach, the application Pods can be created and deleted without issues: files are stored safely, and any application replica can quickly access them. At the same time, the file system on Kubernetes nodes will not be filled with unnecessary files.

Keep in mind that you can only store data you can afford to lose in a container. All other data must be stored in the appropriate database/storage. This approach is endorsed by many, e.g. you can find it in the best practices by Google Cloud engineers.