http2_max_concurrent_streams 128;
http2_recv_timeout 60s;
# 通过客户端 SETTINGS 帧协商更大的初始窗口
# 或服务端主动发送 WINDOW_UPDATE 扩大窗口

// src/http/v2/ngx_http_v2.h
#define NGX_HTTP_V2_MAX_FRAME_SIZE  16384

// 帧发送核心结构体，固化单帧发送状态，无抢占标识
typedef struct {
    ngx_http_v2_connection_t  *h2c;
    ngx_http_v2_stream_t      *stream;
    u_char                    *pos;
    u_char                    *end;
    // 无帧抢占、无动态拆分字段，一旦发送只能串行完成
} ngx_http_v2_frame_t;

// src/http/v2/ngx_http_v2_send.c
static ngx_int_t
ngx_http_v2_send_chain(ngx_http_v2_connection_t *h2c, ngx_chain_t *out)
{
    ngx_http_v2_frame_t  *frame;

    // 核心逻辑：帧入队后串行发送，无抢占调度机制
    while (out) {
        // 按最大帧粒度切割数据，但不支持中断正在发送的帧
        frame = ngx_http_v2_alloc_frame(h2c, NGX_HTTP_V2_FRAME_DATA);
        // 严格限制单帧最大尺寸，固化调度粒度
        ngx_http_v2_fill_data_frame(frame, out, NGX_HTTP_V2_MAX_FRAME_SIZE);
        
        // 帧入队后强制串行执行，无法插队
        ngx_http_v2_queue_frame(h2c, frame);
        out = out->next;
    }

    // 无优先级插队、无帧中断、无动态拆分逻辑
    return ngx_http_v2_flush_frames(h2c);
}

// 流优先级权重、依赖关系结构体
typedef struct {
    ngx_uint_t  weight;       // 流权重
    ngx_uint_t  parent;       // 父依赖流ID
    ngx_queue_t queue;        // 批量调度队列
    // 无实时刷新、无动态插队字段
} ngx_http_v2_priority_t;

// src/http/v2/ngx_http_v2_priority.c
static ngx_http_v2_stream_t *
ngx_http_v2_schedule_frames(ngx_http_v2_connection_t *h2c)
{
    ngx_queue_t              *q;
    ngx_http_v2_stream_t     *stream;
    ngx_http_v2_priority_t   *prio;

    // 缺陷1：批量遍历所有活跃流，CPU开销随并发流线性增长
    // 缺陷2：仅周期批量排序，不实时响应新流优先级
    for (q = ngx_queue_head(&h2c->streams);
         q != ngx_queue_sentinel(&h2c->streams);
         q = ngx_queue_next(q))
    {
        stream = ngx_queue_data(q, ngx_http_v2_stream_t, queue);
        prio = &stream->priority;
        
        // 仅按历史权重批量排序，无即时插队逻辑
        if (ngx_http_v2_stream_ready(stream)) {
            return stream;
        }
    }

    return NULL;
}

// 连接级全局流控窗口（所有流共享，无优先级隔离）
typedef struct {
    ngx_int_t  send_window;   // 连接全局剩余可发送字节
    ngx_int_t  recv_window;   // 连接接收窗口
    // 无核心/普通业务配额拆分字段
} ngx_http_v2_connection_t;

// 单流独立流控窗口
typedef struct {
    ngx_int_t  send_window;   // 单流剩余可发送字节
    ngx_int_t  recv_window;
} ngx_http_v2_stream_t;

// src/http/v2/ngx_http_v2_flow_control.c
ngx_int_t
ngx_http_v2_check_window(ngx_http_v2_stream_t *stream, size_t size)
{
    ngx_http_v2_connection_t  *h2c = stream->h2c;

    // 双层窗口叠加校验：任一窗口不足，直接阻塞发送
    // 场景：单流窗口充足、全局窗口耗尽 → 全流阻塞
    if (h2c->send_window <= 0 || stream->send_window <= 0) {
        return NGX_ERROR; // 直接终止数据发送，触发流控阻塞
    }

    // 窗口配额扣减，无优先级区分
    h2c->send_window -= size;
    stream->send_window -= size;

    return NGX_OK;
}

// 窗口更新被动响应逻辑，无主动推送机制
static ngx_int_t
ngx_http_v2_state_window_update(ngx_http_v2_connection_t *h2c,
    ngx_http_v2_frame_t *frame)
{
    ngx_uint_t  increment;

    // 仅解析客户端被动上报的窗口增量
    increment = ngx_http_v2_get_uint32(frame->pos);
    
    // 被动更新窗口，滞后于数据消耗
    h2c->send_window += increment;
    h2c->stream->send_window += increment;

    // 无主动兜底更新、无阈值触发更新逻辑
    return NGX_OK;
}