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/java_springboot/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/java_springboot/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/java_springboot/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/java_springboot/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/java_springboot/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/java_springboot/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.

Installing dependencies

Enable the necessary dependencies in pom.xml :

...
<dependency>
	<groupId>io.minio</groupId>
	<artifactId>minio</artifactId>
	<version>8.2.1</version>
</dependency>
... <dependency> <groupId>io.minio</groupId> <artifactId>minio</artifactId> <version>8.2.1</version> </dependency>

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 :

package io.werf.werfguidesapp.controllers;

import io.werf.werfguidesapp.components.MinioComponent;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import java.io.ByteArrayInputStream;
import java.io.InputStream;

@RestController
public class MinioController {

	@Autowired
	private MinioComponent minioComponent;

	public MinioController() {

	}

	@PostMapping("/upload")
	public String uploadFileToMinIO(@RequestParam("file") MultipartFile file) {
		try {
			InputStream in = new ByteArrayInputStream(file.getBytes());
			String fileName = file.getOriginalFilename();
			minioComponent.putObject(fileName, in);
			return "File uploaded.";
		} catch (Exception e) {
			e.printStackTrace();
		}
		return "Something wrong.";
	}

	@GetMapping("/download")
	public String downloadFile() throws Exception {
		return minioComponent.getObject("file.txt");
	}
}
package io.werf.werfguidesapp.controllers; import io.werf.werfguidesapp.components.MinioComponent; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.multipart.MultipartFile; import java.io.ByteArrayInputStream; import java.io.InputStream; @RestController public class MinioController { @Autowired private MinioComponent minioComponent; public MinioController() { } @PostMapping("/upload") public String uploadFileToMinIO(@RequestParam("file") MultipartFile file) { try { InputStream in = new ByteArrayInputStream(file.getBytes()); String fileName = file.getOriginalFilename(); minioComponent.putObject(fileName, in); return "File uploaded."; } catch (Exception e) { e.printStackTrace(); } return "Something wrong."; } @GetMapping("/download") public String downloadFile() throws Exception { return minioComponent.getObject("file.txt"); } }

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

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: Add an init container for configuring MinIO to the Deployment. It will start before the main application starts and will wait for MinIO to be ready (thus preventing the application from crashing during startup due to MinIO unavailability):

apiVersion: apps/v1
kind: Deployment
metadata:
  name: werf-guide-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: werf-guide-app
  template:
    metadata:
      labels:
        app: werf-guide-app
    spec:
      imagePullSecrets:
      - name: registrysecret
      initContainers:
      - 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 our MinIO instance.
          mc alias set minio http://minio:9000 minioadmin minioadmin

          # Creating a bucket for our application.
          mc mb --ignore-existing minio/werf-guide-app

      containers:
      - name: backend
        image: {{ .Values.werf.image.backend }}
        command: 
        - sh
        - -euc
        - |
          is_mysql_available() {
            tries=$1
            i=0
            while [ $i -lt $tries ]; do
              mysqladmin -h mysql -P 3306 -u root -p=password ping || return 1
              i=$((i+1))
              sleep 1
            done
          }
          # Waiting for `mysqladmin ping` to run 10 times in a row.
          until is_mysql_available 10; do
            sleep 1
          done
          
          java -jar ./app.jar

        ports:
        - containerPort: 8080
        env:
        - name: LOGGING_LEVEL_ORG_SPRINGFRAMEWORK_WEB
          value: INFO
        - name: DB_HOST
          value: mysql
        - name: DB_NAME
          value: werf-guide-app
        - name: DB_USER
          value: root
        - name: DB_PASSWD
          value: password
      - name: frontend
        image: {{ .Values.werf.image.frontend }}
        ports:
        - containerPort: 80
apiVersion: apps/v1 kind: Deployment metadata: name: werf-guide-app spec: replicas: 1 selector: matchLabels: app: werf-guide-app template: metadata: labels: app: werf-guide-app spec: imagePullSecrets: - name: registrysecret initContainers: - 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 our MinIO instance. mc alias set minio http://minio:9000 minioadmin minioadmin # Creating a bucket for our application. mc mb --ignore-existing minio/werf-guide-app containers: - name: backend image: {{ .Values.werf.image.backend }} command: - sh - -euc - | is_mysql_available() { tries=$1 i=0 while [ $i -lt $tries ]; do mysqladmin -h mysql -P 3306 -u root -p=password ping || return 1 i=$((i+1)) sleep 1 done } # Waiting for `mysqladmin ping` to run 10 times in a row. until is_mysql_available 10; do sleep 1 done java -jar ./app.jar ports: - containerPort: 8080 env: - name: LOGGING_LEVEL_ORG_SPRINGFRAMEWORK_WEB value: INFO - name: DB_HOST value: mysql - name: DB_NAME value: werf-guide-app - name: DB_USER value: root - name: DB_PASSWD value: password - name: frontend image: {{ .Values.werf.image.frontend }} ports: - containerPort: 80

Add the configuration for connecting to MinIO:

...
minio.url=minio
minio.accessKey=minioadmin
minio.secretKey=minioadmin
minio.bucket-name=werf-guide-app
minio.secure=false
... minio.url=minio minio.accessKey=minioadmin minio.secretKey=minioadmin minio.bucket-name=werf-guide-app minio.secure=false

We will leave the connection parameters as they are for now (instead of putting them into environment variables) — in the next chapter, we will discuss a more elegant and proper way of doing this

Create a configuration class, pass the application.properties to it and activate MinIO:

package io.werf.werfguidesapp.config;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import io.minio.MinioClient;

@Configuration
public class MinioConfig {

	@Value("${minio.url}")
	private String minioUrl;
	@Value("${minio.accessKey}")
	private String accessKey;
	@Value("${minio.secretKey}")
	private String secretKey;
	@Value("${minio.bucket-name}")
	private String bucketName;
	@Value("${minio.secure}")
	private Boolean minioSecure;

	@Bean
	public MinioClient minioClient() {
		MinioClient minioClient = MinioClient.builder().credentials(accessKey, secretKey)
				.endpoint(minioUrl, 9000, minioSecure).build();
		return minioClient;
	}
}
package io.werf.werfguidesapp.config; import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import io.minio.MinioClient; @Configuration public class MinioConfig { @Value("${minio.url}") private String minioUrl; @Value("${minio.accessKey}") private String accessKey; @Value("${minio.secretKey}") private String secretKey; @Value("${minio.bucket-name}") private String bucketName; @Value("${minio.secure}") private Boolean minioSecure; @Bean public MinioClient minioClient() { MinioClient minioClient = MinioClient.builder().credentials(accessKey, secretKey) .endpoint(minioUrl, 9000, minioSecure).build(); return minioClient; } }

Now, create a component for handling files in MinIO by adding the two main methods, putObject and getObject, to it:

package io.werf.werfguidesapp.components;

import io.minio.GetObjectArgs;
import io.minio.MinioClient;
import io.minio.PutObjectArgs;
import io.minio.errors.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.io.InputStream;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

@Component
public class MinioComponent {

    public MinioComponent() {

    }

    @Autowired
    private MinioClient minioClient;

    @Value("${minio.bucket-name}")
    private String bucketName;

    public void putObject(String objectName, InputStream inputStream) {
        try {
            minioClient.putObject(PutObjectArgs.builder().bucket(bucketName).object(objectName)
                    .stream(inputStream, -1, 10485760).build());

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException ioException) {
                    ioException.printStackTrace();
                }
            }
        }
    }

    public String getObject(String objectName) {
        try (InputStream stream = minioClient
                .getObject(GetObjectArgs.builder()
                        .bucket(bucketName)
                        .object(objectName)
                        .build());) {
            return new String(stream.readAllBytes());
        } catch (ErrorResponseException | InsufficientDataException |
                InternalException | InvalidKeyException | InvalidResponseException |
                IOException | NoSuchAlgorithmException | ServerException |
                XmlParserException | IllegalArgumentException e) {
            e.printStackTrace();
        }
        return "You haven't uploaded anything yet.";
    }
}
package io.werf.werfguidesapp.components; import io.minio.GetObjectArgs; import io.minio.MinioClient; import io.minio.PutObjectArgs; import io.minio.errors.*; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; import java.io.IOException; import java.io.InputStream; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; @Component public class MinioComponent { public MinioComponent() { } @Autowired private MinioClient minioClient; @Value("${minio.bucket-name}") private String bucketName; public void putObject(String objectName, InputStream inputStream) { try { minioClient.putObject(PutObjectArgs.builder().bucket(bucketName).object(objectName) .stream(inputStream, -1, 10485760).build()); } catch (Exception e) { e.printStackTrace(); } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException ioException) { ioException.printStackTrace(); } } } } public String getObject(String objectName) { try (InputStream stream = minioClient .getObject(GetObjectArgs.builder() .bucket(bucketName) .object(objectName) .build());) { return new String(stream.readAllBytes()); } catch (ErrorResponseException | InsufficientDataException | InternalException | InvalidKeyException | InvalidResponseException | IOException | NoSuchAlgorithmException | ServerException | XmlParserException | IllegalArgumentException e) { e.printStackTrace(); } return "You haven't uploaded anything yet."; } }

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:

┌ Concurrent builds plan (no more than 5 images at the same time)
│ Set #0:
│ - ⛵ image frontend
│ - ⛵ image backend
└ Concurrent builds plan (no more than 5 images at the same time)

┌ ⛵ image frontend
│ Use cache image for frontend/dockerfile
│      name: <DOCKER HUB USERNAME>/werf-guide-app:4d7fe10a14b3d39d37a747bf016e9e8557c5a6d7061cea9d57f2ffd0-1640809566489
│        id: 4325c3e47f17
│   created: 2021-12-29 23:26:06 +0300 MSK
│      size: 9.6 MiB
└ ⛵ image frontend (1.98 seconds)

┌ ⛵ image backend
│ Use cache image for backend/dockerfile
│      name: <DOCKER HUB USERNAME>/werf-guide-app:08454d39888855040def10d02d3687964e8484eca19b9208a10ab2de-1643016826637
│        id: 6eae976ee732
│   created: 2022-01-24 12:33:46 +0300 MSK
│      size: 243.9 MiB
└ ⛵ image backend (3.26 seconds)

┌ Waiting for release resources to become ready
│ ┌ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ │ curl: (7) Failed to connect to minio port 9000: Connection refused
│ │ curl: (7) Failed to connect to minio port 9000: Connection refused
│ └ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ 
│ ┌ Status progress
│ │ DEPLOYMENT                                                                                                  REPLICAS            AVAILABLE             UP-TO-DATE                           
│ │ werf-guide-app                                                                                              2/1                 1                     1                                    
│ │ │   POD                                      READY          RESTARTS            STATUS                      ---                                                                            
│ │ ├── guide-app-6c7cbc8b8b-pw7qf               2/2            2                   Running                     Waiting for: replicas 2->1                                                     
│ │ └── guide-app-778cf48fb7-z8jqf               0/2            0                   Init: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                                    
│ └ Status progress
│ 
│ ┌ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ │ curl: (7) Failed to connect to minio port 9000: Connection refused
│ │ curl: (7) Failed to connect to minio port 9000: Connection refused
│ │ curl: (7) Failed to connect to minio port 9000: Connection refused
│ └ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ 
│ ┌ Status progress
│ │ DEPLOYMENT                                                                                                  REPLICAS            AVAILABLE             UP-TO-DATE                           
│ │ werf-guide-app                                                                                              2/1                 1                     1                                    
│ │ │   POD                                      READY          RESTARTS            STATUS                      ---                                                                            
│ │ ├── guide-app-6c7cbc8b8b-pw7qf               2/2            2                   Running                     Waiting for: replicas 2->1                                                     
│ │ └── guide-app-778cf48fb7-z8jqf               0/2            0                   Init:0/1                    
│ │ 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                                    
│ └ Status progress
│ 
│ ┌ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ │ Added `minio` successfully.
│ │ Bucket created successfully `minio/werf-guide-app`.
│ └ deploy/werf-guide-app po/werf-guide-app-778cf48fb7-z8jqf container/setup-minio logs
│ 
│ ┌ Status progress
│ │ DEPLOYMENT                                                                                                  REPLICAS            AVAILABLE             UP-TO-DATE                           
│ │ werf-guide-app                                                                                              2/1                 1                     1                                    
│ │ │   POD                                      READY          RESTARTS            STATUS                      ---                                                                            
│ │ ├── guide-app-6c7cbc8b8b-pw7qf               2/2            2                   Running                     Waiting for: replicas 2->1                                                     
│ │ └── guide-app-778cf48fb7-z8jqf               0/2            0                   PodInitializing             
│ │ 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                                    
│ └ Status progress
│ 
│ ┌ Status progress
│ │ DEPLOYMENT                                                                                                  REPLICAS            AVAILABLE             UP-TO-DATE                           
│ │ werf-guide-app                                                                                              2->1/1              1                     1                                    
│ │ │   POD                                      READY          RESTARTS            STATUS                                                                                                     
│ │ ├── guide-app-6c7cbc8b8b-pw7qf               2/2            2                   Running -> Terminating      
│ │ └── guide-app-778cf48fb7-z8jqf               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                                    
│ └ Status progress
└ Waiting for release resources to become ready (41.20 seconds)

Release "werf-guide-app" has been upgraded. Happy Helming!
NAME: werf-guide-app
LAST DEPLOYED: Mon Jan 24 12:36:55 2022
NAMESPACE: werf-guide-app
STATUS: deployed
REVISION: 52
TEST SUITE: None
Running time 47.57 seconds

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

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

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