Plugin SPI

Plugin SPI

Plugin interface

get_versions()

Returns all available versions of the plugin. Depending on the plugin, this version may map directly to the HDFS version, or it may not; check your plugin’s documentation. It is responsibility of the plugin to make sure that all required images for each hadoop version are available, as well as configs and whatever else that plugin needs to create the Hadoop cluster.

Returns: list of strings representing plugin versions

Example return value: [“1.2.1”, “2.3.0”, “2.4.1”]

get_configs( hadoop_version )

Lists all configs supported by the plugin with descriptions, defaults, and targets for which this config is applicable.

Returns: list of configs

Example return value: ((“JobTracker heap size”, “JobTracker heap size, in MB”, “int”, “512”, “mapreduce”, “node”, True, 1))

get_node_processes( hadoop_version )

Returns all supported services and node processes for a given Hadoop version. Each node process belongs to a single service and that relationship is reflected in the returned dict object. See example for details.

Returns: dictionary having entries (service -> list of processes)

Example return value: {“mapreduce”: [“tasktracker”, “jobtracker”], “hdfs”: [“datanode”, “namenode”]}

get_required_image_tags( hadoop_version )

Lists tags that should be added to OpenStack Image via Image Registry. Tags are used to filter Images by plugin and hadoop version.

Returns: list of tags

Example return value: [“tag1”, “some_other_tag”, …]

validate( cluster )

Validates a given cluster object. Raises a SaharaException with a meaningful message in the case of validation failure.

Returns: None

Example exception: <NotSingleNameNodeException {code=’NOT_SINGLE_NAME_NODE’, message=’Hadoop cluster should contain only 1 NameNode instance. Actual NN count is 2’ }>

validate_scaling( cluster, existing, additional )

To be improved.

Validates a given cluster before scaling operation.

Returns: list of validation_errors

update_infra( cluster )

This method is no longer used now that Sahara utilizes Heat for OpenStack resource provisioning, and is not currently utilized by any plugin.

Returns: None

configure_cluster( cluster )

Configures cluster on the VMs provisioned by sahara. In this function the plugin should perform all actions like adjusting OS, installing required packages (including Hadoop, if needed), configuring Hadoop, etc.

Returns: None

start_cluster( cluster )

Start already configured cluster. This method is guaranteed to be called only on a cluster which was already prepared with configure_cluster(…) call.

Returns: None

scale_cluster( cluster, instances )

Scale an existing cluster with additional instances. The instances argument is a list of ready-to-configure instances. Plugin should do all configuration operations in this method and start all services on those instances.

Returns: None

get_edp_engine( cluster, job_type )

Returns an EDP job engine object that supports the specified job_type on the given cluster, or None if there is no support. The EDP job engine object returned must implement the interface described in Elastic Data Processing (EDP) SPI. The job_type is a String matching one of the job types listed in Job Types.

Returns: an EDP job engine object or None

decommission_nodes( cluster, instances )

Scale cluster down by removing a list of instances. The plugin should stop services on the provided list of instances. The plugin also may need to update some configurations on other instances when nodes are removed; if so, this method must perform that reconfiguration.

Returns: None

on_terminate_cluster( cluster )

When user terminates cluster, sahara simply shuts down all the cluster VMs. This method is guaranteed to be invoked before that, allowing the plugin to do some clean-up.

Returns: None

get_open_ports( node_group )

When user requests sahara to automatically create a security group for the node group (auto_security_group property set to True), sahara will call this plugin method to get a list of ports that need to be opened.

Returns: list of ports to be open in auto security group for the given node group

get_edp_job_types( versions )

Optional method, which provides the ability to see all supported job types for specified plugin versions.

Returns: dict with supported job types for specified versions of plugin

recommend_configs( self, cluster, scaling=False )

Optional method, which provides recommendations for cluster configuration before creating/scaling operation.

get_image_arguments( self, hadoop_version ):

Optional method, which gets the argument set taken by the plugin’s image generator, or NotImplemented if the plugin does not provide image generation support. See Image Generation.

Returns: A sequence with items of type sahara.plugins.images.ImageArgument.

pack_image( self, hadoop_version, remote, test_only=False, … ):

Optional method which packs an image for registration in Glance and use by Sahara. This method is called from the image generation CLI rather than from the Sahara api or engine service. See Image Generation.

Returns: None (modifies the image pointed to by the remote in-place.)

validate_images( self, cluster, test_only=False, image_arguments=None ):

Validates the image to be used to create a cluster, to ensure that it meets the specifications of the plugin. See Image Generation.

Returns: None; may raise a sahara.plugins.exceptions.ImageValidationError

Object Model

Here is a description of all the objects involved in the API.

Notes:

  • clusters and node_groups have ‘extra’ fields allowing the plugin to persist any supplementary info about the cluster.

  • node_process is just a process that runs on some node in cluster.

Example list of node processes:

  1. jobtracker

  2. namenode

  3. tasktracker

  4. datanode

  • Each plugin may have different names for the same processes.

Config

An object, describing one configuration entry

Property

Type

Description

name

string

Config name.

description

string

A hint for user, what this config is used for.

config_type

enum

possible values are: ‘string’, ‘integer’, ‘boolean’, ‘enum’.

config_values

list

List of possible values, if config_type is enum.

default_value

string

Default value for config.

applicable_target

string

The target could be either a service returned by get_node_processes(…) call in form of ‘service:<service name>’, or ‘general’.

scope

enum

Could be either ‘node’ or ‘cluster’.

is_optional

bool

If is_optional is False and no default_value is specified, user must provide a value.

priority

int

1 or 2. A Hint for UI. Configs with priority 1 are always displayed. Priority 2 means user should click a button to see the config.

User Input

Value provided by user for a specific config.

Property

Type

Description

config

config

A config object for which this user_input is provided.

value

Value for the config. Type depends on Config type.

Instance

An instance created for cluster.

Property

Type

Description

instance_id

string

Unique instance identifier.

instance_name

string

OpenStack instance name.

internal_ip

string

IP to communicate with other instances.

management_ip

string

IP of instance, accessible outside of internal network.

volumes

list

List of volumes attached to instance. Empty if ephemeral drive is used.

nova_info

object

Nova instance object.

username

string

Username, that sahara uses for establishing remote connections to instance.

hostname

string

Same as instance_name.

fqdn

string

Fully qualified domain name for this instance.

remote

helpers

Object with helpers for performing remote operations.

Node Group

Group of instances.

Property

Type

Description

name

string

Name of this Node Group in Cluster.

flavor_id

string

OpenStack Flavor used to boot instances.

image_id

string

Image id used to boot instances.

node_processes

list

List of processes running on each instance.

node_configs

dict

Configs dictionary, applied to instances.

volumes_per_node

int

Number of volumes mounted to each instance. 0 means use ephemeral drive.

volumes_size

int

Size of each volume (GB).

volumes_mount_prefix

string

Prefix added to mount path of each volume.

floating_ip_pool

string

Floating IP Pool name. All instances in the Node Group will have Floating IPs assigned from this pool.

count

int

Number of instances in this Node Group.

username

string

Username used by sahara to establish remote connections to instances.

configuration

dict

Merged dictionary of node configurations and cluster configurations.

storage_paths

list

List of directories where storage should be placed.

Cluster

Contains all relevant info about cluster. This object is is provided to the plugin for both cluster creation and scaling. The “Cluster Lifecycle” section below further specifies which fields are filled at which moment.

Property

Type

Description

name

string

Cluster name.

project_id

string

OpenStack Project id where this Cluster is available.

plugin_name

string

Plugin name.

hadoop_version

string

Hadoop version running on instances.

default_image_id

string

OpenStack image used to boot instances.

node_groups

list

List of Node Groups.

cluster_configs

dict

Dictionary of Cluster scoped configurations.

cluster_template_id

string

Cluster Template used for Node Groups and Configurations.

user_keypair_id

string

OpenStack keypair added to instances to make them accessible for user.

neutron_management_network

string

Neutron network ID. Instances will get fixed IPs in this network.

anti_affinity

list

List of processes that will be run on different hosts.

description

string

Cluster Description.

info

dict

Dictionary for additional information.

Validation Error

Describes what is wrong with one of the values provided by user.

Property

Type

Description

config

config

A config object that is not valid.

error_message

string

Message that describes what exactly is wrong.

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