deb-sahara/doc/source/devref/plugin.spi.rst

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 edp.spi. The job_type is a String matching one of the job types listed in edp_spi_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-gen.

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

pack_image( self, hadoop_version, remote, reconcile=True, ... ):

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-gen.

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

validate_images( self, cluster, reconcile=True, 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-gen.

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 if 'use_neutron' config is set to True.
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.