Proxy: Make Redis and Memory LB TTL configurable

[liukun4515]

Summary

Fixes #4647

Makes the hardcoded TTL values in Redis and Memory load balancers configurable through environment variables, allowing customers to adjust them based on their scenarios.

Problem

Currently, the TTL values are hardcoded:

• ServerAliveDuration = 300s (5 minutes)
• HLSAliveDuration = 120s (2 minutes)
• RTCAliveDuration = 120s (2 minutes)

For some scenarios, 300 seconds is too long, and customers need the ability to configure these values.

Solution

Added three new configurable environment variables:

• PROXY_SERVER_ALIVE_DURATION (default: 300s)
• PROXY_HLS_ALIVE_DURATION (default: 120s)
• PROXY_RTC_ALIVE_DURATION (default: 120s)

Usage Examples

Reduce server TTL to 60 seconds:

PROXY_SERVER_ALIVE_DURATION=60s ./srs-proxy

Custom TTL for all values:

PROXY_SERVER_ALIVE_DURATION=180s \
PROXY_HLS_ALIVE_DURATION=90s \
PROXY_RTC_ALIVE_DURATION=90s \
./srs-proxy

Changes

1. env.go: Added three new methods to Environment interface and their implementations
2. lb.go: Replaced hardcoded constants with configurable helper functions
3. mem.go: Updated MemoryLoadBalancer.Pick() to use configurable duration
4. redis.go: Updated RedisLoadBalancer to use configurable TTL for all Redis keys

Testing

• ✅ Code compiles successfully
• ✅ All TTL values are logged on startup for visibility
• ✅ Defaults match previous hardcoded values (backward compatible)

Files Changed

• proxy/internal/env/env.go: +27, -1
• proxy/internal/lb/lb.go: +28, -6
• proxy/internal/lb/mem.go: +5, -1
• proxy/internal/lb/redis.go: +19, -5

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