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Keystone-schema-in-cassandra

Revision as of 06:22, 30 April 2015 by Ajaya Agrawal (talk | contribs) (The credential Table)

Introduction

The purpose of this wiki article is to describe the Cassandra tables for each of the backends of Keystone. A discussion of the general concepts related to schema design in Cassandra has been covered separately.

Identity

The identity backend of Keystone holds data for users, groups and user-group membership. There are three tables in the MySQL DB for this purpose.

  • user
  • group
  • user_group_membership

The user Table

The user table in MySQL is as follows.

user
id domain_id name enabled password extra default_project_id
Primary Key: (id), Unique Key: (domain_id, name)

The operations on this table are as follows.

  • create_user(user_id, user)
  • delete_user(user_id)
  • update_user(domain_id, user_id, user)
  • get_user(user_id)
  • get_user_by_name(domain_id, name)
  • list_users(domain_id)


From these it is evident that the data for user is queried on either (domain_id), or (domain_id, name), or (user_id). The equivalent operations in Cassandra, subject to eventual consistency, are supported by the following two tables.

user
id domain_id name enabled password extra default_project_id
Primary Key: (id)
name_index
domain_id name id
Primary Key: (domain_id, name)

The group table

The group table in MySQL is similar to the user table, and is as follows.

group
id domain_id name extra description
Primary Key: (id), Unique Key: (domain_id, name)

Keeping the equivalent data in Cassandra is done similarly to what was done with the user table, i.e., with two Cassandra tables as follows.

group
id domain_id name extra description
Primary Key: (id)
group_name_index
domain_id name id
Primary Key: (domain_id, name)

The user_group_membership Table

The user_group_membership table used in MySQL is as follows.

user_group_membership
user_id group_id
Primary Key: (user_id, group_id), Key: (group_id)

The operations performed on this table are as follows.

  • add_user_to_group(user_id, group_id)
  • check_user_in_group(user_id, group_id)
  • remove_user_from_group(user_id, group_id)
  • list_users_in_group(group_id)
  • list_groups_for_user(group_id)

There are two types of operations here. One is based on user_id and another is based on group_id. So there are two tables in Cassandra to store user_group_membership. All the insert, update and delete go to both the tables in Cassandra.

user_group
user_id group_id
Primary Key: (user_id, group_id); clustering column: group_id
group_user
group_id user_id
Primary Key: (group_id, user_id); clustering column: user_id

Assignment

The assignment backend holds data about the role assignments. It additionally has a role_backend which stores data for all the roles. There are two tables in the MySQL DB.

  • assignment
  • role

The assignment Table

The assignment table in MySQL is as follows.

type actor_id target_id role_id
Primary Key: (type, actor_id, target_id, role_id), Key: (actor_id), Key: (role_id)

The equivalent in Cassandra is

assignment
type actor_id target_id role_id
Primary Key: (type, actor_id, target_id, role_id), Secondary Indices: (target_id) and (role_id)

There are a number of operations on this backend. All the operations are not written here for brevity. This table looks the same in Cassandra. There are two secondary index on columns target_id and role_id. These would come handy when a role_id or target_id is deleted from Keystone.

The role Table

The role table in MySQL is as follows.

role
id name extra
Primary Key: (id), Unique Key: (name)

Most of the operations on this table are done based on role_id. There is an api in v2.0 which allows the client to get a role by its name. So we need the name to id mapping in second table. To preserve the uniqueness of the name, a row is first inserted to the role_name_index table. If that succeeds then the row is inserted to the role table. The equivalent in Cassandra is two tables.

role
id name extra
Primary Key: (id)
role_name_index
name id
Primary Key: (name)

Resource

The resource backend holds data about projects and domains. There are two tables in this backend.

  • project
  • domain

The project Table

The project table in MySQL is as follows.

project
id domain_id name enabled description extra parent_id
Primary Key:(id), Unique Key: (domain_id, name), Key: (parent_id)

This table is going under heavy changes at the time of this writing. Currently, this design does not account for Hierarchical Multi Tenancy, which will be accounted for later. If we leave out the parent_id part in this table, then this table looks exactly similar to user table and also is modeled exactly the same.

The domain Table

The domain table in MySQL is as follows.

domain
id name extra
Primary Key: (id), Unique Key: (name)

Again this table looks the same as role table and is modeled similarly to it.

Credential

The Credential backend holds data related to EC2 credentials. It has one table.

The credential Table

The credential table in MySQL is as follows.

credential
id user_id project_id blob type extra
Primary Key: (id)

The table has the same schema in Cassandra as well.

credential
id user_id project_id blob type extra
Primary Key: (id)

Trust

The Trust backend stores data related to trust delegation functionality offered to users.

The trust Table

The trust table in MySQL is as follows.

trust
id trustor_user_id trustee_user_id project_id impersonation deleted_at expires_at remaining_uses extra roles
Primary Key: (id)

This table has the same schema in Cassandra as well.