FileConfigurator Operator

The FileConfigurator operator allows configuring systems tuned by Akamas by interpolating configuration parameters into files on remote machines.

The operator performs the following operations:

1. It reads an input file from a remote machine containing templates for interpolating the configuration parameters generated by Akamas

2. It replaces the values of configuration parameters in the input file

3. It writes the file with replaced configuration parameters on a specified path on another remote machine

Access on remote machines is performed using SFTP (SSH).

Templates for configuration parameters

The FileConfigurator allows writing templates for configuration parameters in two ways:

• specify that a parameter should be interpolated directly:

${component_name.parameter_name}

• specify that all parameters of a component should be interpolated:

${component_name.*}

Suffix or prefix for interpolated parameters

It is possible to add a prefix or suffix to interpolated configuration parameters by acting at the component-type level:

Notice that any parameter that does not contain the FileConfigurator element in the operators' attribute is ignored and not written.

name: Component Type 1
description: My Component type
parameters:
- name: x1
  domain:
    type: real
    domain: [-5.0, 10.0]
  defaultValue: -5.0
  # Under this section, the operator to be used to configure the parameters is defined
  operators:
    FileConfigurator:
      # using this OPTIONAL confTemplate property is possible to interpolate the parameter value with a prefix and a suffix
      confTemplate: "PREFIX${value}SUFFIX"

In the example above, the parameter x1 will be interpolated with the prefix PREFIX and the suffix SUFFIX, ${value} will be replaced with the actual value of the parameter at each experiment.

Example

Let's assume we want to apply the following configuration:

component1.param1: 1024
component1.param2: Category1
component2.param3: 7
component2.param4: 35.4

where component1 is of type MyComponentType and MyComponentType is defined as follows:

name: MyComponentType
description: "MyComponentType
parameters:
- name: param1
  domain:
    type: real
    domain: [-5.0, 10.0]
  defaultValue: -5.0
  # Under this section, the operator to be used to configure the parameters is defined
  operators:
    FileConfigurator:
      # using this OPTIONAL confTemplate property is possible to interpolate the parameter value with a prefix and a suffix
      confTemplate: "X1:${value}MB"
...

A template file to interpolate only parameter component1.param1 and all parameters from component2 would look like this:

myexecutable.sh -PARAM ${component1.param1} -PARAMS ${component2.*}

The file after the configuration parameters are interpolated would look like this:

myexecutable.sh -PARAM X1:1024MB -PARAMS 7 35.4

Note that the file in this example contains a bash command whose arguments are constructed by interpolating configuration parameters. This represents a typical use case for the File Configurator: to construct the right bash commands that will configure a system with the new configuration parameters computed by Akamas.

Operator arguments

Name	Type	Value Restrictions	Required	Default	Description
source	Object	should have a structure like the one defined in the next section	no, if the Component whose name is defined in component has properties that map to the ones defined within source		Information relative to the source/input file to be used to interpolate optimal configuration parameters discovered by Akamas
target	Object	should have a structure like the one defined in the next section	no, if the Component whose name is defined in component has properties that map to the ones defined within target		Information relative to the target/output file to be used to interpolate optimal configuration parameters discovered by Akamas
component	String	should match the name of an existing Component of the System under test	no		The name of the Component whose properties can be used as arguments of the operator
ignoreUnsubstitutedTokens	Boolean		no	False	Behavior of the operator regarding leftover tokens in the target file. When False, FileConfigurator fails. When True , FileConfigurator succeeds regardless of leftover tokens

source and target structures and arguments

Here follows the structure of either the source or target operator argument

Name	Type	Value restrictions	Required	Default	Description
hostname	String	should be a valid SSH host address	yes		SSH endpoint
username	String		yes		SSH login username
password	String	cannot be set if key is already set	no		SSH login password
sshPort	Number	1≤sshPort≤65532	no	22	SSH port
key	String	cannot be set if password is already set	no		SSH login key, provided directly its value or the path of the file to import from. The operator supports RSA and DSA Keys
path	String	should be a valid path	yes		The path of the file to be used either as the source or target of the activity to applying Akamas computed configuration parameters using files

Get operator arguments from component

The component argument can be used to refer to a component by name and use its properties as the arguments of the operator. In case the mapped arguments are already provided to the operator, there is no override.

In this case, the operator replaces in the template file only tokens referring to the specified component. A parameter bound to any component will cause the substitution to fail.

Component property to operator argument mapping

Component property	Operator argument
hostname	source->hostname target->hostname
username	source->username target->username
sshPort	source->sshPort target->sshPort
password	source->password target->password
key	source->key target->key
sourcePath	source->path
targetPath	target->path

Examples

Configure parameters for an Apache server with explicit source and target machine information

name: RemoteConfOperatorTestStandalone
operator: FileConfigurator
arguments:
  source:
    hostname: template-server
    username: akamas-user1
    password: akamas-password1
    path: /templates/frontend-httpd.conf
  target:
    hostname: frontend-server
    username: akamas-user2
    password: akamas-password22
    path: /etc/httpd/httpd.conf

Configure parameters for an Apache server with information taken from a Component

name: RemoteConfOperatorTestStandalone
operator: FileConfigurator
arguments:
  component: apache-server-1

where the apache-server-1 component is defined as:

name: apache-server-1
description: The Apache server instance
componentType: Apache Server 2.4

properties:
  hostname: apache.akamas.io
  username: ubuntu
  key: key.pem
  sourcePath: templates/httpd.conf.template
  targetPath: /etc/httpd/httpd.conf