从你的描述来看，服务器资源使用率很低但无法处理更高并发请求，这通常表明存在连接处理或网络配置相关的瓶颈。以下是几个关键优化方向：

1. Go HTTP 服务器配置优化

package main

import (
    "net/http"
    "time"
    "github.com/julienschmidt/httprouter"
)

func main() {
    router := httprouter.New()
    router.GET("/api/0.2/weather", weatherHandler)
    
    server := &http.Server{
        Addr:         ":7000",
        Handler:      router,
        ReadTimeout:  10 * time.Second,    // 增加读取超时
        WriteTimeout: 10 * time.Second,    // 增加写入超时
        IdleTimeout:  30 * time.Second,    // 空闲连接超时
    }
    
    // 设置连接限制
    server.SetKeepAlivesEnabled(true)
    server.ListenAndServe()
}

func weatherHandler(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    // 直接从内存返回数据
    data := map[string]interface{}{
        "temperature": 25,
        "humidity":    60,
        "condition":   "sunny",
    }
    
    w.Header().Set("Content-Type", "application/json")
    // 直接写入响应，避免不必要的序列化开销
    w.Write([]byte(`{"temperature":25,"humidity":60,"condition":"sunny"}`))
}

2. 系统级优化配置

# 优化 /etc/sysctl.conf 配置
net.core.somaxconn = 65535
net.core.netdev_max_backlog = 10000
net.ipv4.tcp_max_syn_backlog = 65536
net.ipv4.tcp_max_tw_buckets = 2000000
net.ipv4.ip_local_port_range = 1024 65535
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.tcp_keepalive_intvl = 30
net.ipv4.tcp_keepalive_probes = 3

# 应用配置
sysctl -p

3. 连接池和 Goroutine 优化

import (
    "net"
    "net/http"
    "time"
)

func createOptimizedClient() *http.Client {
    transport := &http.Transport{
        MaxIdleConns:        1000,
        MaxIdleConnsPerHost: 1000,
        IdleConnTimeout:     90 * time.Second,
        DialContext: (&net.Dialer{
            Timeout:   30 * time.Second,
            KeepAlive: 30 * time.Second,
        }).DialContext,
        TLSHandshakeTimeout: 10 * time.Second,
        ExpectContinueTimeout: 1 * time.Second,
    }
    
    return &http.Client{
        Transport: transport,
        Timeout:   30 * time.Second,
    }
}

4. 监控和诊断代码

import (
    "expvar"
    "net/http"
    "runtime"
)

func init() {
    // 暴露运行时指标
    expvar.Publish("goroutines", expvar.Func(func() interface{} {
        return runtime.NumGoroutine()
    }))
}

// 添加性能监控中间件
func monitoringMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        start := time.Now()
        next.ServeHTTP(w, r)
        duration := time.Since(start)
        
        // 记录请求耗时
        // 可以集成到监控系统中
        _ = duration
    })
}

5. 压力测试优化参数

# 使用 wrk 进行更准确的测试
wrk -t12 -c4000 -d30s http://ip:7000/api/0.2/weather

# 或者使用优化后的 ab 参数
ab -n 10000 -c 1000 -k http://ip:7000/api/0.2/weather

主要问题可能在于：

1. TCP 连接队列溢出
2. 文件描述符限制
3. 客户端端口耗尽
4. 网络延迟导致的连接超时

建议先应用系统级优化，然后使用保持连接的测试方法（-k 参数）来验证性能改进。