Configuring custom domain mappings for your function

Domain mappings provide the URL route to your Code Engine function within a project. With Code Engine, these mappings are automatically created, by default, whenever you deploy your function. However, you can map your own custom domain to a Code Engine function to route requests from your custom URL to your function from the Code Engine console or CLI.

If you want to target your function with a domain that you own, you can use a custom domain mapping. When you set a custom domain mapping in Code Engine, you define a 1-to-1 mapping between your fully qualified domain name (FQDN) and a Code Engine function in your project.

A custom domain mapping must point to only one mapping. However, you can configure multiple domain mappings to a single function.

You can create at most 80 custom domain mappings per project. See Project quotas.

When you create a custom domain mapping in Code Engine, the domain name that you use in the mapping must be unique in the region.

To create and set up custom domain mappings, complete these steps:

Review the Considerations before you use custom domain mappings in Code Engine.
Obtain your custom domain from a domain registrar (outside of Code Engine).
Configure a custom domain mapping in Code Engine for your function (from the Code Engine console or CLI).
Complete the custom domain configuration with your domain registrar. (outside of Code Engine).

Suppose that you want to create a custom domain mapping for www.example.com and shop.example.com. In this case, you must create a custom domain mapping for each unique domain or subdomain. However, you can reuse the same TLS secret for multiple custom domain mappings if the certificates of the TLS secret includes the domain that is specified in the custom domain mapping. This means that you can map a TLS secret to multiple domains, such as www.example.com and shop.example.com, or to a wildcard domain such as *.example.com.

Configuring custom domain mappings from the console

You can create a custom domain mapping with your Code Engine function to your registered domain name with the Code Engine console.

Before you begin

In this scenario, create a custom domain mapping to a function with a TLS secret. For example, create a custom domain mapping to map the www.example.com domain to the myfunction function.

From the Code Engine Projects page, go to your project.
From the Overview page, click Domain mappings.
From the Domain mappings page, click Create to create your mapping.
From the Create a domain mapping page, specify the TLS secret to use with this domain mapping. Code Engine validates whether the certificate is signed by a trusted CA, and whether the certificate matches the provided custom domain name and private key.

To create a new TLS secret,
1. Click Create.
2. Add the TLS certificate, including all intermediate certificates, which are associated with your domain. If the certificate is provided to you as separate files, concatenate the content of the files. You can provide this information in a file.
3. Add the private key that corresponds to your certificate. You can provide this information in a file.
Example format for a certificate chain
```
-----BEGIN CERTIFICATE-----
...certificate...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
...intermediate-certificate...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
...intermediate-certificate...
-----END CERTIFICATE-----
```
Or, to use an existing TLS secret,
1. Click Select.
2. Select the existing secret from the list that you want to use.
Specify the domain name and target component.
- Specify the fully qualified domain name for your custom domain name; for example, www.example.com.
- Select an existing target function; for example, myfunction. For this example, the myfunction function uses the icr.io/codeengine/helloworld sample image. For more information about the code that is used for this example, see helloworld.
- Notice the CNAME target field. This value is the CNAME entry that is required when you complete the custom domain configuration with your domain registrar so that traffic that targets your custom domain is routed to the specified function.
Click Create to create the custom domain mapping.

Now you have a domain mapping that is created in Code Engine. However, requests that are sent to your function are not (yet) routed to your custom domain. Next, complete the custom domain configuration with your domain registrar.

Suppose that you want to create a custom domain mapping for www.example.com and shop.example.com. In this case, you must create a custom domain mapping for each unique domain or subdomain. However, you can reuse the same TLS secret for multiple custom domain mappings if the TLS secret includes certification for the domain that is specified in the custom domain mapping. The TLS secret can contain certificates that map to specific multiple domains, such as www.example.com and shop.example.com, or a wildcard domain such as *.example.com. Note that you cannot use the wildcard domain more than one time within a region.

Configuring custom domain mappings with the CLI

To create a custom domain mapping with the CLI, use the domainmapping create command. This command requires a fully qualified domain name (FQDN), such as www.example.com, a target function, and a TLS secret. For a complete listing of options, see the ibmcloud ce domainmapping create command.

Before you begin

Obtain the registered domain name.
Obtain the signed TLS certificate and the private key for your custom domain.
Set up your Code Engine CLI environment.
Create a project.
Create a function.

When your domain name is registered, you have a signed TLS certificate and its matching private key for this domain, and you have an existing Code Engine function, you are ready to add a custom domain mapping . You can use the domainmapping create command in the CLI to create a custom domain mapping with your Code Engine function.

Create a TLS secret with the signed TLS certificate and the private key. In this example, the mycert.txt file contains the TLS certificate, including all intermediate certificates, which are associated with your domain. If the certificate is provided to you as separate files, concatenate the content of the files. The myprivatekey.txt file contains the matching private key that corresponds to the certificate chain.
```
ibmcloud ce secret create --name mytlssecret --format tls --cert-chain-file  mycertchain.txt --private-key-file myprivatekey.txt
```
Example output
```
Creating tls secret 'mytlssecret'...
OK
```
Create the custom domain mapping between the Code Engine myfunction function and the custom domain, www.example.com. Use the TLS secret that you created in the previous step.
```
ibmcloud ce domainmapping create --domain-name www.example.com --target myhellofun --tls-secret mytlssecret
```
Example output
```
OK
Domain mapping successfully created.
```

The following table summarizes the options that are used with the domainmapping create command in this example. For more information about the command and its options, see the ibmcloud ce domainmapping create command.

Table 1. Command description
Option	Description
`--domain-name`	The name of the custom domain mapping. Specify the name of your custom domain, such as `www.example.com`. This value is required.
`--target`	The name of the target Code Engine function. This value is required.
`--tls-secret`	The TLS secret for the domain mapping. This value is required.

Now your custom domain mapping is created in Code Engine. However, requests that are sent to your function are not (yet) routed to your custom domain. Next, you must complete the custom domain configuration with your domain registrar.

Completing the custom domain configuration with your domain registrar

After the Code Engine custom domain mapping is created, a CNAME record that matches the fully qualified domain name must be added to the DNS settings of the custom domain. You can find the DNS settings in the configuration settings of the corresponding domain registrar. Complete this step so that traffic that targets your custom domain is routed to the Code Engine function as defined in your Code Engine custom domain mapping.

Testing your custom domain

After you complete the custom domain configuration with your domain registrar and the CNAME record updates are published, you can test the function with the custom domain mapping.

With a browser, call the function by targeting the custom domain with the curl command.

curl -v -X GET https://www.example.com

The output of the call to the custom domain is mapped to the myhellofun function, which uses the icr.io/codeengine/helloworld sample image.