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Build and Push to ECR

Amazon ECR is a fully managed service from AWS that you can use to store and manage Docker images securely and reliably. In addition, ECR provides a simple web-based interface for creating, managing, and sharing Docker images and integrating them with other AWS services. For more information, go to the AWS documentation on Pushing a Docker image.

In Harness CI, you can use a Build and Push to ECR step to build an image from your codebase and push it to your Amazon ECR container registry repo. This is one of several options for building and pushing artifacts in Harness CI.

You need:

Kubernetes cluster build infrastructures require root access

With Kubernetes cluster build infrastructures, Build and Push steps use kaniko. Other build infrastructures use drone-docker. Kaniko requires root access to build the Docker image. It doesn't support non-root users.

If your build runs as non-root (runAsNonRoot: true), and you want to run the Build and Push step as root, you can set Run as User to 0 on the Build and Push step to use the root user for that individual step only.

If your security policy doesn't allow running as root, go to Build and push with non-root users.

Add a Build and Push to ECR step

In your pipeline's Build stage, add a Build and Push to ECR step and configure the settings accordingly.

Here is a YAML example of a minimum Build and Push to ECR step.

              - step:
type: BuildAndPushECR
name: BuildAndPushECR_1
identifier: BuildAndPushECR_1
spec:
connectorRef: YOUR_AWS_CONNECTOR_ID
region: us-east-1
account: "12345"
imageName: test-image
tags:
- latest

When you run a pipeline, you can observe the step logs on the build details page. If the Build and Push to ECR step succeeds, you can find the uploaded image in your ECR repo.

Build and Push to ECR step settings

The Build and Push to ECR step has the following settings. Depending on the stage's build infrastructure, some settings might be unavailable or optional. Settings specific to containers, such as Set Container Resources, are not applicable when using the step in a stage with VM or Harness Cloud build infrastructure.

Name

Enter a name summarizing the step's purpose. Harness automatically assigns an Id (Entity Identifier) based on the Name. You can change the Id.

AWS Connector

Select the Harness AWS connector to use to connect to ECR.

This step supports all AWS connector authentication methods (AWS access key, delegate IAM role assumption, IRSA, and cross-account access), but an additional stage variable might be required to assume IAM roles or use ARNs.

The AWS IAM roles and policies associated with the AWS account for your Harness AWS connector must allow pushing to ECR. For more information, go to the AWS connector settings reference.

If you're using Harness Cloud build infrastructure, the Connectivity Mode must be Connect through Harness Platform.

Stage variable required to assume IAM role or use ARNs

Stages with Build and Push to ECR steps must have a PLUGIN_USER_ROLE_ARN stage variable if:

To add the PLUGIN_USER_ROLE_ARN stage variable:

  1. In the Pipeline Studio, select the stage with the Build and Push to ECR step, and then select the Overview tab.
  2. In the Advanced section, add a stage variable.
  3. Enter PLUGIN_USER_ROLE_ARN as the Variable Name, set the Type to String, and then select Save.
  4. For the Value, enter the full ARN value.
    • For cross-account roles, this ARN value must correspond with the AWS connector's ARN.
    • For connectors that use the delegate's IAM role, the ARN value must identify the role you want the build pod/machine to use.

Region

Define the AWS region to use when pushing the image.

The registry format for ECR is AWS_ACCOUNT_ID.dkr.ecr.REGION.amazonaws.com, and a region is required. For more information, go to the AWS documentation on Pushing a Docker image.

Account Id

The AWS account ID to use when pushing the image. This is required.

The registry format for ECR is aws_account_id.dkr.ecr.region.amazonaws.com. For more information, go to the AWS documentation for Pushing a Docker image.

Image Name

The name of the image you are pushing. It can be any name.

Tags

Add Docker build tags. This is equivalent to the -t flag.

Add each tag separately.

tip

When you push an image to a repo, you tag the image so you can identify it later. For example, in one pipeline stage, you push the image, and, in a later stage, you use the image name and tag to pull it and run integration tests on it.

Harness expressions are a useful way to define tags. For example, you can use the expression <+pipeline.sequenceId> as a tag. This expression represents the incremental build identifier, such as 9. By using a variable expression, rather than a fixed value, you don't have to use the same image name every time.

For example, if you use <+pipeline.sequenceId> as a tag, after the pipeline runs, you can see the Build Id in the output.

And you can see where the Build Id is used to tag your image:

Later in the pipeline, you can use the same expression to pull the tagged image, such as myrepo/myimage:<+pipeline.sequenceId>.

Base Image Connector

Select an authenticated connector to download base images from a Docker-compliant registry. If you do not specify a Base Image Connector, the step downloads base images without authentication. Specifying a Base Image Connector is recommended because unauthenticated downloads generally have a lower rate limit than authenticated downloads.

Optimize

With Kubernetes cluster build infrastructures, select this option to enable --snapshotMode=redo. This setting causes file metadata to be considered when creating snapshots, and it can reduce the time it takes to create snapshots. For more information, go to the kaniko documentation for the snapshotMode flag.

For information about setting other kaniko runtime flags, go to Environment variables.

Dockerfile

The name of the Dockerfile. If you don't provide a name, Harness assumes the Dockerfile is in the root folder of the codebase.

Context

Enter a path to a directory containing files that make up the build's context. When the pipeline runs, the build process can refer to any files found in the context. For example, a Dockerfile can use a COPY instruction to reference a file in the context.

Labels

Specify Docker object labels to add metadata to the Docker image.

Build Arguments

The Docker build-time variables. This is equivalent to the --build-arg flag.

Target

The Docker target build stage, equivalent to the --target flag, such as build-env.

Remote Cache Image

Use this setting to enable remote Docker layer caching where each Docker layer is uploaded as an image to a Docker repo you identify. If the same layer is used in later builds, Harness downloads the layer from the Docker repo. You can also specify the same Docker repo for multiple Build and Push steps, enabling these steps to share the same remote cache. This can dramatically improve build time by sharing layers across pipelines, stages, and steps.

For Remote Cache Image, enter the name of the remote cache registry and image, for example, app/myImage.

The remote cache repository must be in the same account and organization as the build image. For caching to work, the specified image name must exist.

Environment Variables (plugin runtime flags)

Build and Push steps use plugins to complete build and push operations. With Kubernetes cluster build infrastructures, these steps use kaniko, and, with other build infrastructures, these steps use drone-docker.

These plugins have a number of additional runtime flags that you might need for certain use cases. For information about the flags, go to the kaniko plugin documentation and the drone-docker plugin documentation.

In Build and Push steps, you use the Environment Variables setting to set these plugin runtime flags. You must input a Name and Value for each variable. Format the name as PLUGIN_FLAG_NAME.

warning

Unlike in other Harness CI steps, the Environment Variables setting in Build and Push steps only accepts the known plugin runtime flags. You must set other types of environment variables in your Dockerfile, build arguments, or as stage variables, depending on their usage and purpose in your build.

YAML example: Build and Push step with environment variables

This YAML example shows a Build and Push to GAR step with PLUGIN environment variables.

              - step:
identifier: pushGCR
name: push GCR
type: BuildAndPushGAR ## Type depends the selected Build and Push step, such as Docker, GAR, ACR, and so on.
spec: ## Some parts of 'step.spec' vary by Build and Push step type (Docker, GAR, ACR, etc).
connectorRef: YOUR_GCR_CONNECTOR
host: "us.gcr.io"
projectID: "some-gcp-project"
imageName: "some-image-name"
tags:
- "1.0"
- "1.2"
buildArgs:
foo: bar
hello: world
labels:
foo: bar
hello: world
target: dev-env
context: "."
dockerfile: "harnessDockerfile"
remoteCacheImage: "test/cache"
envVariables: ## Specify plugin runtime flags as environment variables under 'step.spec'.
PLUGIN_TAR_PATH: ./harnesstarpath
PLUGIN_IMAGE_DOWNLOAD_RETRY: "2"
PLUGIN_COMPRESSED_CACHING: "false"
PLUGIN_USE_NEW_RUN: "true"
PLUGIN_GARBAGE: yoyo

For example, to set --skip-tls-verify for kaniko, add an environment variable named PLUGIN_SKIP_TLS_VERIFY and set the variable value to true.

              - step:
identifier: buildandpush
name: buildandpush
type: BuildAndPush---
spec:
...
envVariables:
PLUGIN_SKIP_TLS_VERIFY: true

To set custom_dns for drone-docker, add an environment variable named PLUGIN_CUSTOM_DNS and set the variable value to your custom DNS address.

                    envVariables:
PLUGIN_CUSTOM_DNS: "vvv.xxx.yyy.zzz"

Plugin runtime flags are also used to build without pushing.

Stage variables

Previously, you could set some plugin runtime flags as stage variables. If you had done this, Harness recommends moving these stage variables to the Environment Variables in your Build and Push step.

For other types of environment variables (that aren't Build and Push plugin runtime flags), stage variables are still inherently available to steps as environment variables. However, where you declare environment variables depends on their usage and purpose in your build. You might need to set them in your Dockerfile, build args, or otherwise.

Run as User

With Kubernetes cluster build infrastructures, you can specify the user ID to use to run all processes in the pod if running in containers. For more information, go to Set the security context for a pod.

This step requires root access. You can use the Run as User setting if your build runs as non-root (runAsNonRoot: true), and you can run the Build and Push step as root. To do this, set Run as User to 0 to use the root user for this individual step only.

If your security policy doesn't allow running as root, go to Build and push with non-root users.

Set Container Resources

Set maximum resource limits for the resources used by the container at runtime:

  • Limit Memory: The maximum memory that the container can use. You can express memory as a plain integer or as a fixed-point number using the suffixes G or M. You can also use the power-of-two equivalents Gi and Mi. The default is 500Mi.
  • Limit CPU: The maximum number of cores that the container can use. CPU limits are measured in CPU units. Fractional requests are allowed; for example, you can specify one hundred millicpu as 0.1 or 100m. The default is 400m. For more information, go to Resource units in Kubernetes.

Timeout

Set the timeout limit for the step. Once the timeout limit is reached, the step fails and pipeline execution continues. To set skip conditions or failure handling for steps, go to:

Conditions, looping, and failure strategies

You can find the following settings on the Advanced tab in the step settings pane:

Troubleshoot Build and Push steps

Go to the CI Knowledge Base for questions and issues related to building and pushing images, such as: