How to Develop Functions

To invoke your function using doctl, use the serverless functions invoke subcommand, replacing sample/hello with the name of your function:

doctl serverless functions invoke sample/hello

The function returns the response body in a JSON object:

{
  "body": "Hello stranger!"
}

Adding the --full flag to doctl serverless functions invoke returns a full activation record, which includes more information about the invocation such as the duration of execution, runtime, response status, and logs. Learn more in the activation records reference.

Invoke a Function with Parameters

To set parameters when invoking a function, use the -p or --param flag and give it a key:value pair.

doctl serverless functions invoke sample/hello --param name:sammy

{
  "body": "Hello sammy!"
}

You can use multiple -p or --param flags to pass more than one key:value pair:

doctl serverless functions invoke sample/hello -p name:sammy -p age:10

You can also format multiple parameters as a single, comma-separated list:

doctl serverless functions invoke sample/hello -p name:sammy,age:10

You can also pass in parameters from a JSON file using the -P or --param-file flags.

The curl command is a common tool for making web requests. All the functions you deploy have a public URL where you can invoke them with curl.

Use the functions get subcommand to find the URL of your function, replacing sample/hello with the name of your function:

doctl serverless functions get sample/hello --url

This command returns a URL similar to the following:

https://faas-nyc1-78edc.doserverless.co/api/v1/web/fn-EXAMPLE-706a-4f13-9c81-f24a3330260b/sample/hello

Use the bare curl command with your URL to fetch a response:

curl https://faas-nyc1-78edc.doserverless.co/api/v1/web/fn-EXAMPLE-706a-4f13-9c81-f24a3330260b/sample/hello

This returns the response body:

Hello stranger!

Invoke a Function with Parameters

You can add parameters to a curl request using the -d flag:

curl https://faas-nyc1-78edc.doserverless.co/api/v1/web/fn-feb132ee-706a-4f13-9c81-f24a3330260b/sample/hello \
  -d 'name=sammy'

You can send multiple parameters using multiple -d flags.

You can also send parameters as JSON using the same flag, but you must also send the appropriate Content-Type header:

curl https://faas-nyc1-78edc.doserverless.co/api/v1/web/fn-feb132ee-706a-4f13-9c81-f24a3330260b/sample/hello \
  -d '{"name":"sammy"}' \
  -H 'Content-Type: application/json'

The Functions control panel interface has a basic text editor for single-file functions and the ability to run functions, pass in parameters, and view output and logs.

To invoke a function in the control panel, click Functions in the left menu, then click a namespace to go to its Overview page.

Then, click the name of the function you want to invoke to go to its Source tab.

To invoke the function, press the green Run button. The function runs and prints output and logs:

The output of the function matches the content type. For example, if your function returns an image, the output section displays the image.

Invoke a Function with Parameters

To send parameters to your function, click the Parameters button next to the green Run button to open the Change Function Input window.

Enter parameters as JSON-formatted text. If your JSON has formatting errors, the lines with issues have red highlights in right-hand margin and the problematic characters are be underlined with red squiggles.

Once your input has no formatting errors, click Save to save the new input.

Click Run again to see the output and logs for your function given the new input parameters.

To retrieve logs from the most recent function activation, use the serverless activations logs subcommand. The default --limit is 1, but this example uses --limit 3 to show the last three activations:

doctl serverless activations logs --limit 3

This returns a header with the activation ID, status, date and time, and function version information, followed by the actual logged output:

=== 49aa4a2bd3834635aa4a2bd383f63514 (success) 05/12 15:55:21 hello:0.0.3
2022-05-12T19:55:21.532898871Z stdout: Hello sammy
=== 918883de63b7403f8883de63b7a03f14 (success) 05/12 15:55:37 hello:0.0.3
2022-05-12T19:55:37.646627522Z stdout: Hello sammy
=== d4e9d0de96c3461aa9d0de96c3e61aa1 (success) 05/13 11:03:06 hello:0.0.5
2022-05-13T15:03:06.910748257Z stdout: Hello sammy

Add the --follow flag to follow the logs as they are generated (like tail -f). You can also filter down to a specific function or package by using the --function or --package flags.

This example tails logs for the sample/hello function:

doctl serverless activations logs --follow --function sample/hello

enter CTRL+C to stop continuously following the logs and return to your command prompt.

Retrieve Full Activation Records

Using the activation ID from the log output, you can retrieve the full activation record for more information:

doctl serverless activations get EXAMPLEdaf34232747f4c7ab34232747f

This returns the full JSON object for an activation, which includes logs, response status, response body, and other details that may be useful for debugging. Learn more in the activation records reference.

You can inspect function activation records and logs in the Logs tab of the current namespace:

Use the Select Function drop-down to filter the records by a package name or a single function name. Use the Select Period drop-down to filter the records by time period.

To view more details about an activation, including logged STDOUT text, click the + disclosure button on the left side of the record:

This displays the complete JSON activation record. The logged STDOUT text is available under logs in the top level of the object. Learn more in the activation records reference.