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Expose a TCP Server via a Service

Choreo offers the flexibility to design and deploy applications in the programming language of your choice. One viable choice for specific network communication needs is TCP (Transmission Control Protocol). TCP provides a reliable, stream-oriented communication mechanism that ensures data integrity and orderliness during transmission. It's the go-to option for scenarios where guaranteed data delivery and error recovery are paramount.

In this guide, you will learn to use Choreo to create a service component that exposes a TCP server implemented in Go, enabling efficient and scalable communication with any TCP client application. No prior knowledge of the Go language is necessary to follow this guide.

By following this guide, you will:

  • Setup a TCP server
    • Create a simple TCP server using a service component.
    • Link the containerized TCP service to the Choreo component using a Dockerfile.
    • Deploy the TCP server component in Choreo.
  • Setup a TCP client
    • Create a TCP client using a manual task component.
    • Link the containerized TCP client to the Choreo component using a Dockerfile.
    • Deploy the TCP client component in Choreo.
  • Invoke the TCP server using a TCP client and observe the response through the Choreo log view.

Prerequisites

Before you try out this guide, complete the following:

  • If you are signing in to the Choreo Console for the first time, create an organization as follows:

    1. Go to https://console.choreo.dev/, and sign in using your preferred method.
    2. Enter a unique organization name. For example, Stark Industries.
    3. Read and accept the privacy policy and terms of use.
    4. Click Create.

    This creates the organization and opens the Project Home page of the default project created for you.

  • Fork the Choreo samples repository, which contains the sample service implementation for this guide.

Let's get started!

Learn the repository file structure

It is important to understand the purpose of the key files in the sample service. The following table provides a brief overview of each file in the sample service.

Note

The following file paths are relative to the path <sample-repository-dir>/docker-tcp-service.

File Path Description
server/main.go The greeter service code written in the Go language.
client/main.go The greeter client application written in the Go language.
Dockerfile.server The Dockerfile to build the container image of the server application.
Dockerfile.client The Dockerfile to build the container image of the client application.
.choreo/component.yaml The Choreo-specific configuration provides information about how Choreo exposes the service.

Configure the service port with endpoints

In Choreo, you can expose your services via endpoints.

Let's run the TCP server service component on port 5050. To securely expose the service through Choreo, you must provide the port and other required information to Choreo. For detailed information on each attribute of an endpoint, see Configure Endpoints.

Choreo looks for an component.yaml file inside the .choreo directory to configure the endpoint details of a containerized component. Place the .choreo directory at the root of the Docker build context path.

In our TCP server sample, the component.yaml file is at docker-tcp-service/.choreo/component.yaml, where the build context path is docker-tcp-service.

Step 1: Create a service component with a TCP endpoint

To create a containerized service component, follow these steps:

  1. Go to https://console.choreo.dev/ and sign in. This opens the project home page.
  2. If you already have one or more components in your project, click + Create. Otherwise, proceed to the next step.
  3. Click the Service card.

  4. Enter a display name, a unique name, and a description for the service component. You can enter the values given below:

    Info

    In the Component Name field, you must specify a name to uniquely identify the component in various contexts. The value is editable only at the time you create the component. You cannot change the name after you create the component.

    Field Value
    Component Display Name Go TCP Server
    Component Name go-tcp-server
    Description Send greetings

  5. Click the GitHub tab.

  6. To allow Choreo to connect to your GitHub account, click Authorize with GitHub. If you have not already connected your GitHub repository to Choreo, enter your GitHub credentials and select the repository you created in the prerequisites section to install the Choreo GitHub App.

    Alternatively, you can paste the Choreo samples repository URL in the Provide Repository URL field to connect to it without requiring authorization from the Choreo Apps GitHub application. However, authorizing the repository with the Choreo GitHub App is necessary if you want to enable Auto Deploy for the component.

    Note

    The Choreo GitHub App requires the following permissions:

    • Read and write access to code and pull requests.
    • Read access to issues and metadata.

    You can revoke access if you do not want Choreo to have access to your GitHub account. However, write access is exclusively utilized for sending pull requests to a user repository. Choreo will not directly push any changes to a repository.

  7. Under Connect Your Repository, enter the following information:

    Field Value
    Organization Your GitHub account
    GitHub Repository choreo-samples
    Branch main

  8. Select Docker as the buildpack.

  9. Enter the following information:

    Field Value
    Docker Context docker-tcp-service
    Dockerfile docker-tcp-service/Dockerfile.server

    Info

    1. To successfully build your container with Choreo, it is essential to explicitly define a User ID (UID) under the USER instruction in your Dockerfile. For reference, see the sample Dockerfile. To ensure that the defined USER instruction is valid, it must conform to the following conditions:

      • A valid User ID is a numeric value between 10000-20000, such as 10001 or 10500.
      • Usernames are considered invalid and should not be used. For example, my-custom-user-12221 or my-custom-user are invalid User IDs.

    2. The Dockerfile utilized in this guide is a multi-stage Dockerfile, which is designed to keep the final image size small and provides the ability to build the application with a specific version of tools and libraries.

  10. Click Create. This creates the component and takes you to the Overview page of the component.

You have successfully created a service from a Dockerfile. Next, you can build and deploy the service.

Step 2: Build and deploy

Now that you have connected the source repository, and configured the endpoint details, it's time to build the service and create an image. Then you can deploy the image and test the service.

Step 2.1: Build

To build the service, follow these steps:

  1. In the left navigation menu, click Build.

  2. On the Build page, click Build Latest.

    Note

    Building the service component may take a while. You can track the progress via the logs in the Build Details pane. Once the build process is complete, the build status changes to Success.

    You can access the following scans under Build.

    • The Dockerfile scan: Choreo performs a scan to check if a non-root user ID is assigned to the Docker container to ensure security. If no non-root user is specified, the build will fail.
    • Container (Trivy) vulnerability scan: This detects vulnerabilities in the final docker image.

    • Container (Trivy) vulnerability scan: The details of the vulnerabilities open in a separate pane. If this scan detects critical vulnerabilities, the build will fail.

      Info

      If you have Choreo environments on a private data plane, you can ignore these vulnerabilities and proceed with the deployment.

Step 2.2: Deploy

To deploy the service, follow these steps:

  1. In the left navigation menu, click Deploy.
  2. On the Set Up card, click Configure & Deploy.
  3. In the Environment Configurations pane that opens, click Next to skip the configuration.
  4. In the File Mount pane, click Next to skip the configuration.

  5. Review the Endpoint Details and click Deploy.

    Note

    Deploying the service component may take a while. Once deployed, the Development environment card indicates the Deployment Status as Active.

  6. Once you have successfully deployed your service, navigate to the component overview page and copy the TCP service address. You need to provide that address when setting up the client application later in this guide.

You have successfully deployed the TCP server. Currently, the TCP service is only accessible by the components deployed within the same project.

Step 3: Invoke the TCP service

Now let's use a TCP client to invoke the TCP service that you created above. To do this, you can create a manual trigger component as the TCP client. This is the recommended approach because, in this example, it's more efficient to have a client that connects to the server, sends a request, and then stops. Here, a continuously executing task isn't required. Furthermore, if you use a manual trigger component, you won't need to expose an endpoint in the client for invocation, unlike with an API.

Step 3.1: Create a manual trigger for the TCP client

To create a manual task component, follow these steps:

  1. On the Choreo Console header, click the Project list and select the project where you created the TCP service component. This opens the project home page.
  2. Go to the Component Listing section and click + Create.
  3. Click the Manual Task card.

  4. Enter a display name, a unique name, and a description for the component. You can enter the values given below:

    Info

    In the Component Name field, you must specify a name to uniquely identify the component in various contexts. The value is editable only at the time you create the component. You cannot change the name after you create the component.

    Field Value
    Component Display Name Go TCP Client
    Component Name go-tcp-client
    Description Receive greetings

  5. Click the GitHub tab.

  6. To allow Choreo to connect to your GitHub account, click Authorize with GitHub. If you have not already connected your GitHub repository to Choreo, enter your GitHub credentials and select the repository you created in the prerequisites section to install the Choreo GitHub App.

    Alternatively, you can paste the Choreo samples repository URL in the Provide Repository URL field to connect to it without requiring authorization from the Choreo Apps GitHub application. However, authorizing the repository with the Choreo GitHub App is necessary if you want to enable Auto Deploy for the component.

    Note

    The Choreo GitHub App requires the following permissions:

    • Read and write access to code and pull requests.
    • Read access to issues and metadata.

    You can revoke access if you do not want Choreo to have access to your GitHub account. However, write access is exclusively utilized for sending pull requests to a user repository. Choreo will not directly push any changes to a repository.

  7. Under Connect Your Repository, enter the following information:

    Field Value
    Organization Your GitHub account
    GitHub Repository choreo-samples
    Branch main

  8. Select Docker as the buildpack.

  9. Enter the following information:

    Field Value
    Docker Context docker-tcp-service
    Dockerfile docker-tcp-service/Dockerfile.client

  10. Click Create. This creates the component and takes you to the Overview page of the component.

Step 3.2: Build the TCP client component

To build the component, follow these steps:

  1. In the left navigation menu, click Build.

  2. On the Build page, click Build Latest.

    Note

    Building the service component may take a while. You can track the progress via the logs in the Build Details pane. Once the build process is complete, the build status changes to Success.

Step 3.3: Setup environment variables and deploy the TCP client

The client application, in this case, the TCP client, requires the server URL of the TCP server service. This is read from the client application as an environment variable. Follow the steps below to configure the environment variable for the client application:

  1. On the Choreo Console left navigation menu, click Deploy.
  2. In the Set Up card, click Configure & Deploy.
  3. In the Environment Configurations pane that opens, click + Add.

  4. Specify the following name and value to configure the environment variable for the client application:

    Field Value
    Name SERVER_ADDRESS
    Value Paste the URL value copied after deploying the TCP service via step 2.2 above. Make sure to drop the tcp:// part and the trailing / from the URL when copying. For example, add only go-tcp-server-1097922445:8080.

  5. Click Add and then click Next.

  6. Click Deploy.

Step 3.4: Execute the TCP client component

To execute the TCP client, follow these steps:

  1. In the left navigation menu, click Execute.
  2. Click Run Now. This triggers the TCP client and generates logs. You can trigger multiple runs to generate multiple logs.

For details on what you can monitor via the execute page, see Monitor executions.