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Update registry cache documentation with adaptive throttling feature

Document the new adaptive throttling feature that prevents cache
penetration when registry is failing and no stale cache exists.

Includes:
- Feature overview
- Usage examples with configuration options
- Explanation of throttling behavior
- Example scenario demonstrating protection

Co-authored-by: asim <17530+asim@users.noreply.github.com>

2026-01-09 12:16:37 +00:00

2.5 KiB

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Registry Cache

Cache is a library that provides a caching layer for the go-micro registry.

If you're looking for caching in your microservices use the selector.

Features

Caching: Caches registry lookups with configurable TTL
Stale Cache Fallback: Returns stale cached data when registry is unavailable
Singleflight Protection: Deduplicates concurrent requests for the same service
Adaptive Throttling: Rate limits failed lookups to prevent cache penetration (new in v5)

Interface

// Cache is the registry cache interface
type Cache interface {
	// embed the registry interface
	registry.Registry
	// stop the cache watcher
	Stop()
}

Usage

Basic Usage

import (
	"github.com/micro/go-micro/registry"
	"github.com/micro/go-micro/registry/cache"
)

r := registry.NewRegistry()
cache := cache.New(r)

services, _ := cache.GetService("my.service")

Advanced Configuration

import (
	"time"
	"github.com/micro/go-micro/registry"
	"github.com/micro/go-micro/registry/cache"
)

r := registry.NewRegistry()

// Configure cache with custom options
cache := cache.New(r,
	cache.WithTTL(2*time.Minute),                    // Cache TTL
	cache.WithMinimumRetryInterval(10*time.Second),  // Throttle failed lookups
)

services, _ := cache.GetService("my.service")

Adaptive Throttling

When the registry is unavailable and there's no stale cache to return, the cache now throttles retry attempts to prevent overwhelming the registry:

Default behavior: Failed lookups are throttled for 5 seconds
Configurable: Use WithMinimumRetryInterval() to adjust the interval
Protection scope: Per-service throttling (different services can be retried independently)
Recovery: Throttling is cleared on successful lookup

Example Scenario

cache := cache.New(etcdRegistry, cache.WithMinimumRetryInterval(10*time.Second))

// First lookup when etcd is down
_, err := cache.GetService("api")  // → Calls etcd, fails, records failure time

// Immediate retry (< 10s later)
_, err = cache.GetService("api")  // → Throttled, returns ErrNotFound immediately

// After 10 seconds
time.Sleep(10 * time.Second)
_, err = cache.GetService("api")  // → Allowed to retry, calls etcd again

This prevents cache penetration scenarios where thousands of concurrent requests hammer a failing registry.

2.5 KiB 原始文件 永久链接 Blame 文件历史