GCP负载均衡：Target Pools、Backend Services与Regional Backend Service差异咨询

Totally get the confusion here—GCP's load balancing backend options can overlap in terminology but serve very distinct purposes. Let's break down each one clearly so you can pick the right fit for your use case:

1. Target Pools #

Think of Target Pools as the old-school, layer 4-focused backend component, built exclusively for TCP/UDP Network Load Balancers. They don't touch any HTTP(S)-level logic—just raw packet forwarding.

• Core traits:
  • Supports only TCP/UDP protocols; no layer 7 features like path routing or cookie-based session affinity.
  • Works with managed/unmanaged instance groups, and includes basic health checks (TCP, HTTP, or HTTPS, but only for simple reachability).
  • Limited security integrations (can pair with Cloud Armor, but lacks the advanced rules available for HTTP(S) backends).
• Best for: Pure TCP/UDP services like databases, custom TCP APIs, or any workload where you don't need HTTP-specific features.

2. Global Backend Services #

This is the go-to backend for global external HTTP(S) Load Balancers, built to handle layer 7 traffic at scale across GCP regions.

• Core traits:
  • Fully optimized for HTTP/HTTPS traffic, with support for advanced layer 7 features: path/host-based routing, cookie-sticky sessions, request rewriting, and rate limiting.
  • Can connect to a variety of backend types: instance groups, Cloud Functions, Cloud Run services, and even Backend Buckets for static content hosting.
  • Includes granular health checks (e.g., checking for specific HTTP status codes or response content).
  • Integrates seamlessly with GCDN (Google Cloud CDN) for cached content delivery, and advanced Cloud Armor security policies.
  • Routes traffic globally to the closest healthy backend, minimizing latency for end users worldwide.
• Best for: Public-facing HTTP/HTTPS services that need global reach, CDN support, or advanced layer 7 routing.

3. Regional Backend Services #

This is the regional counterpart to global backend services, designed for region-specific HTTP(S) load balancing (both internal and regional external).

• Core traits:
  • Limited to a single GCP region—no cross-region traffic routing, which keeps latency low for local users and avoids inter-region data transfer costs.
  • Shares most layer 7 features with global backend services: path routing, session affinity, granular health checks, and Cloud Armor integration.
  • Works with region-local resources: instance groups, Cloud Functions, and Cloud Run services within the same region.
• Best for:
  • Internal VPC-based services (like microservices communicating within a region) that need HTTP(S) load balancing.
  • External services whose user base is concentrated in a single region (no need for global distribution).
  • Workloads that require tight integration with region-specific resources (e.g., regional Cloud SQL instances).

Quick Feature Comparison #

In short:

• Use Target Pools for pure TCP/UDP workloads with Network Load Balancers.
• Use Global Backend Services for global HTTP/HTTPS services needing scale and advanced features.
• Use Regional Backend Services for region-locked HTTP/HTTPS workloads (internal or local external).

内容的提问来源于stack exchange，提问作者Prashant Bhate