LinuxConfigurator Operator

The LinuxConfigurator operator allows configuring systems tuned by Akamas by applying parameters related to the Linux kernel using different strategies.

The operator can configure provided Components or can configure every Component which has parameters related to the Linux kernel.

The parameters are applied via SSH protocol.

Operator arguments

Name	Type	Value Restrictions	Required	Default	Description
component	String	It should match the name of an existing Component of the System under test	No		The name of the Component for which available Linux kernel parameters will be configured

If no component is provided, this operator will try to configure every parameter defined for the Components of the System under test

- name: LinuxConf
  operator: LinuxConfigurator
  arguments:
    component: ComponentName

Example

In this example, the Operator is used to automatically the OS parameters of the specified component.

- name: LinuxConf
  operator: LinuxConfigurator
  arguments:
    component: OS_serveraml

component structure and arguments

The following table describes the component structure and arguments.

Name	Type	Value Restrictions	Required	Default	Description
username	String		Yes		SSH login username
key	Multiline string		Yes		SSH login key, provided directly its value or the path of the file to import from. The operator supports RSA and DSA Keys
blockDevices	List of objects	It should have a structure like the one described here below	No		Allows the user to restrict and specify to which block-device apply block-device-related parameters
networkDevices	List of objects	It should have a structure like the one described here below	No		Allows the user to restrict and specify to which network-device apply network-device-related parameters

blockDevices and networkDevices structure and arguments

The properties blockDevices and networkDevices allow to speficify which parameters to apply each block and network device associated with the Component, as well as which block and network device should be left untouched by the LinuxConfigurator operator_._

If the properties are omitted, then all block and network devices associated with the Component will be configured will all the available related parameters.

Notice: all block devices called _loopN _ (where N is an integer number greater or equal to 0) are automatically excluded from the Component’s block devices.

The properties blockDevices and networkDevices are lists of objects with the following structure:

Name	Type	Value Restrictions	Required	Default
name	String	It should be a valid regular expression to match block/network-devices	Yes		A regular expression that matches block/network-devices to configure with related parameters of the Component
parameters	List of strings	It should contain the names of matching parameters of the Component	No		The list of parameters to be configured for the specified block/network-devices. If the list is empty, then no parameter will be applied for the block/network-devices matched by name

Examples

In the following example, only the parameters os_StorageReadAhead _ and os_StorageQeueuScheduler _ are applied to all the devices that match the regex ‘xvd[a-z]’ (i.e. xvda, xvdb, …, xvdc):

blockDevices:
- name: "xvd[a-z]"
  parameters:
    - os_StorageReadAhead
    - os_StorageQueueScheduler

In the following example, only the parameter os_StorageMaxSectorKb is applied to block device xvdb and loop0:

blockDevices:
- name: "xvdb|loop0"
  parameters:
    - os_StorageMaxSectorsKb

Also notice that in this example, the parameter is applied also to the block device loop0, since it is explicitly specified in the name filter, which overrides the default behavior since loopN devices are excluded by the Linux Optimization Pack.

In the following example, no parameters are applied to the wlp4s0 network device, which is therefore excluded from the optimization:

networkDevices:
  - name: wlp4s0
    parameters: []

Strategies

Several strategies are supported by this operator which, depending on the specific strategy, can be specified at ComponentType and at each parameter level.

Sysctl strategy

With this strategy, a parameter is configured by leveraging the sysctl utility. The sysctl variable to map to the parameter that needs to be configured is specified using the key argument.

name: Component Type 1
description: My Component type
parameters:
  - name: net_forwarding
    domain:
      type: integer
      domain: [0, 1]
    defaultValue: 1
    operators:
      # the parameter is configured using LinuxConfigurator
      LinuxConfigurator:
        sysctl:
          key: net.ipv4.forwarding

Echo strategy

With this strategy, a parameter is configured by echoing and piping its value into a provided file. The path of the file is specified using the file argument.

name: Component Type 1
description: My Component type
parameters:
  - name: os_MemoryTransparentHugepageEnabled
    domain:
      type: categorical
      categories: [always, never]
    defaultValue: always
    operators:
      LinuxConfigurator:
        echo:
          file: /sys/kernel/mm/transparent_hugepage/enabled

Map strategy

With this strategy, each possible value of a parameter is mapped to a command to be executed on the machine the LinuxConfigurator operates on(this is especially useful for categorical parameters).

name: Component Type 1
description: My Component type
parameters:
  - name: os_MemorySwap
    domain:
      type: categorical
      categories: [swapon, swapoff]
    defaultValue: swapon
    operators:
      LinuxConfigurator:
        map:
          swapon: command1
          swapoff: command2

Command strategy

With this strategy, a parameter is configured by executing a command into which the parameter value is interpolated.

name: Component Type 1
description: My Component type
parameters:
  - name: os_MemorySwap
    domain:
      type: categorical
      categories: [swapon, swapoff]
    defaultValue: swapon
    operators:
      LinuxConfigurator:
        command:
          cmd: sudo ${value} -a