Metadata "relax"

The relax metadata makes an action tolerant to internal errors. It returns an error instead of throwing it.

Type: boolean|string|array|regexp
Default: false

Sometimes, you wish to handle errors not in the action itself but after its execution or inside another sibling action executed after.

Usage

The value is a boolean with the value false as default. Simply set the action to a value true to enable the "relax" behavior.

In the example below, we start the MariaDB service with the systemctl command. If the service is not installed or already started, the result is a non-zero code, resulting in an error unless the relax metadata is activated, but we don't want to deal with it:

nikita
.execute({
  $relax: true,  command: 'systemctl start mariadb'
})

Error output

The relax metadata doesn't throw an error. Any error sent by the "handler" function is available as the error property of the action output object:

(async () => {
  const {error} = await nikita
  .execute({
    $relax: true,    command: 'invalid command'
  })
  console.info(error)
})()

The error is an extended Error object that provides a context of the action execution with a specific Nikita error code:

NikitaError: NIKITA_EXECUTE_EXIT_CODE_INVALID: an unexpected exit code was encountered, command is "invalid command", got 127 instead of 0.
    at Object.module.exports [as error] (/Users/serg/dev/adaltas/production/node-nikita/packages/core/lib/utils/error.js:36:10)
    at Immediate.<anonymous> (/Users/serg/dev/adaltas/production/node-nikita/packages/core/lib/actions/execute/index.js:573:31)
    at processImmediate (internal/timers.js:439:21) {
  code: 'NIKITA_EXECUTE_EXIT_CODE_INVALID',
  '$status': false,
  stdout: '',
  stderr: '/bin/sh: invalid: command not found\n',
  command: 'invalid command',
  exit_code: 127
}

String value

When a string is passed as relax metadata value, it is interpreted as a code of returning error. Thus, you can enable the relax behavior only for specific errors. For example, if a command is not found, Nikita trows an error with NIKITA_EXECUTE_EXIT_CODE_INVALID code that you can skip:

nikita
.execute({
  $relax: 'NIKITA_EXECUTE_EXIT_CODE_INVALID',  command: 'invalid command'
})

Array's values

Array's values are similar to string value enabling relax behavior for multiple error codes:

nikita
.execute({
  $relax: ['NIKITA_EXECUTE_EXIT_CODE_INVALID', 'ANOTHER_CODE'],  command: 'invalid command'
})

Regular expression value

The relax metadata accepts a regular expression as a value. It matches an error code against a regular expression:

nikita
.execute({
  $relax: /^NIKITA_/,  command: 'invalid command'
})

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