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Deep Dive into OpenStack Placement

Understanding OpenStack's Resource Management Service

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Understanding OpenStack Placement

Placement is OpenStack's resource management service that provides a centralized system for tracking and managing physical and virtual resources in the cloud. It was introduced in the Newton release and has evolved into a crucial component since the Stein version, working closely with Nova and other OpenStack services.

What is Placement?

The Resource Management Layer

Placement serves as the central resource manager in OpenStack, providing essential functionality:

  • Resource Tracking: Monitors physical and virtual resources (RAM, vCPU, storage, IP)
  • Standardized Units: Manages resources using standardized Resource Classes
  • Service Integration: Supports efficient resource allocation for Nova, Neutron, and Cinder
  • API-Driven: Provides RESTful APIs for resource management and allocation

By centralizing resource management, Placement enables optimal resource utilization and efficient scheduling across the OpenStack cloud.

graph LR A[OpenStack Placement] A --> B[Core Services] A --> C[Resource Types] A --> D[Integration Points] A --> E[Management Features] B --> B1[Resource Tracking] B --> B2[Allocation Management] B --> B3[API Services] B --> B4[Database] C --> C1[Compute Resources] C --> C2[Network Resources] C --> C3[Storage Resources] D --> D1[Nova Integration] D --> D2[Neutron Integration] D --> D3[Cinder Integration] E --> E1[Resource Classes] E --> E2[Allocation Policies] E --> E3[Usage Monitoring] style A stroke:#333,stroke-width:1px,fill:#f5f5f5 style B stroke:#333,stroke-width:1px,fill:#a5d6a7 style C stroke:#333,stroke-width:1px,fill:#64b5f6 style D stroke:#333,stroke-width:1px,fill:#ffcc80 style E stroke:#333,stroke-width:1px,fill:#ce93d8


Placement Architecture and Components

Placement employs a modular architecture with a central API server and database that work together to provide comprehensive resource management services. This design enables efficient resource tracking and allocation across the OpenStack cloud.

Core Components

Component Role Description
Placement API Resource Management Service
  • Provides RESTful API for resource management
  • Processes resource allocation requests
  • Maintains resource state in the database
  • Validates and authorizes resource operations
Placement Database Resource State Storage
  • Stores resource provider information
  • Maintains allocation records
  • Tracks resource usage and availability
  • Manages resource class definitions
Nova Integration Compute Resource Management
  • Coordinates with Nova-compute for resource updates
  • Supports Nova-scheduler in node selection
  • Manages instance resource allocation
  • Provides health check functionality

Resource Management Flow

sequenceDiagram participant Nova as "Nova Service" participant Placement as "Placement API" participant DB as "Placement DB" participant Compute as "Compute Node" Nova->>Placement: Request Resource Allocation Placement->>DB: Check Resource Availability DB-->>Placement: Return Available Resources Placement-->>Nova: Provide Allocation Options Nova->>Compute: Deploy Instance Compute->>Placement: Update Resource Usage Placement->>DB: Update Resource State

Resource Types and Classes

Resource Management Categories

Placement manages various types of resources:

  • Compute Resources: CPU, RAM, disk space, and custom compute resources
  • Network Resources: IP addresses, VLANs, VXLANs, and QoS policies
  • Storage Resources: Block storage, object storage, and custom storage resources
  • Custom Resources: User-defined resource classes for specific workloads

Each resource type is managed through standardized resource classes, enabling consistent tracking and allocation across the cloud.


Key Features and Capabilities

Placement provides a comprehensive set of features for resource management, enabling efficient allocation, tracking, and optimization of cloud resources.

Resource Management Features

Feature Description
Resource Tracking
  • Real-time monitoring of resource usage and availability
  • Support for both physical and virtual resources
  • Dynamic updates from compute nodes
  • Comprehensive resource state management
Allocation Management
  • Efficient resource allocation for new instances
  • Support for resource reservation and quotas
  • Dynamic resource reallocation
  • Multi-tenant resource isolation
Policy Management
  • Custom resource allocation policies
  • Project-specific resource limits
  • Workload-specific optimization rules
  • Quality of Service (QoS) policies

Integration with OpenStack Services

Service Integration Points

Placement integrates with various OpenStack services:

  • Nova Integration: Provides resource information for instance scheduling and deployment
  • Neutron Integration: Manages network resource allocation and tracking
  • Cinder Integration: Coordinates storage resource allocation
  • Custom Service Integration: Supports integration with additional OpenStack services

This integration enables comprehensive resource management across the entire OpenStack cloud.


Usage and Best Practices

Effective use of Placement requires understanding its capabilities and implementing appropriate resource management strategies. Here are key considerations and best practices for utilizing Placement effectively.

Resource Management Strategies

Strategy Description Benefits
Resource Classes Define standardized resource types for consistent management
  • Consistent resource tracking
  • Simplified allocation policies
  • Better resource utilization
Allocation Policies Implement custom policies for resource allocation
  • Optimized resource distribution
  • Workload-specific optimization
  • Improved performance
Monitoring Regular tracking of resource usage and availability
  • Proactive resource management
  • Early problem detection
  • Better capacity planning

Implementation Guidelines

Best Practices

For effective Placement implementation:

  • Resource Planning: Carefully plan resource classes and allocation policies
  • Monitoring: Implement comprehensive resource monitoring
  • Integration: Ensure proper integration with all OpenStack services
  • Documentation: Maintain clear documentation of resource management policies

Following these guidelines helps ensure efficient resource management and optimal cloud performance.


Key Points

💡 Placement Essentials
  • Core Functionality
    - Centralized resource management for OpenStack clouds
    - Real-time resource tracking and allocation
    - Integration with Nova and other OpenStack services
    - Support for custom resource classes and policies
  • Architecture
    - RESTful API for resource management
    - Database for resource state storage
    - Integration with Nova components
    - Support for various resource types
  • Key Features
    - Comprehensive resource tracking
    - Efficient allocation management
    - Custom policy support
    - Service integration capabilities


References