内容简介:lua-nginx-module 源码分析之共享内存字典
在 ngx_lua
的世界里,共享内存被组织成“共享内存字典”,也就是 ngx.shared.DICT
,截至 0.10.8 版本, ngx_lua
提供了 17 个操作共享内存字典的 API,这些 API 提高了编程的灵活性,让共享内存以 Lua table 的形式展现在我们的面前,而且无需我们关心竞态问题,所有的操作都是原子性的,这大大提高了 ngx_lua
工程师的开发效率.
本文将会着眼于共享内存字典的内部实现,对源码进行透彻的分析. 这里认为读者在阅读此文时,已经对 Nginx
和 ngx_lua
有了一定的认识. 注意,下文将会涉及到共享内存字典相关的每个函数(暂时不包括 ffi
),因此代码量比较大!
API
lua_shared_dict
允许我们添加共享内存字典. 这条指令工作在 http 配置块下.
lua_shared_dict dog 1m;
ngx_lua
共享内存字典一共有 17 个 API.
- ngx.shared.DICT.get
- ngx.shared.DICT.get_stale
- ngx.shared.DICT.set
- ngx.shared.DICT.add
- ngx.shared.DICT.safe_add
- ngx.shared.DICT.safe_set
- ngx.shared.DICT.incr
- ngx.shared.DICT.flush_all
- ngx.shared.DICT.flush_expired
- ngx.shared.DICT.get_keys
- ngx.shared.DICT.replace
- ngx.shared.DICT.delete
- ngx.shared.DICT.lpush
- ngx.shared.DICT.rpush
- ngx.shared.DICT.lpop
- ngx.shared.DICT.rpop
- ngx.shared.DICT.llen
详细介绍请参考 文档
Internel Structure
直观来看,共享内存字典就是一张 Lua table,每一对 key-value 在内部都以一个 ngx_http_lua_shdict_node_t
的实例存在(下文称之为节点),为了提高检索效率,所有节点被组织成红黑树,同时这些节点又都在一个 LRU 队列上,这是为了快速淘汰节点而设计的. 事实上这种设计也在其他的 Nginx 模块里出现过,比如 ngx_http_limit_req_module
.
typedef struct { u_char color; /* 事实上这块内存总是连在 ngx_rbtree_node_t 后面 */ uint8_t value_type; /* 值的类型 */ u_short key_len; /* 键的长度 */ uint32_t value_len; /* 值的长度 */ uint64_t expires; /* 过期时间 */ ngx_queue_t queue; /* LRU 队列节点 */ uint32_t user_flags; /* 用户设置的标志 */ u_char data[1]; /* 键字符串的第一个字符 */ };
value_type 用一个枚举类型来表示,目前值类型有
enum { SHDICT_TNIL = 0, /* nil */ SHDICT_TBOOLEAN = 1, /* bool */ SHDICT_TNUMBER = 3, /* number */ SHDICT_TSTRING = 4, /* string */ SHDICT_TLIST = 5, /* list,这是一个特殊的双端队列类型 */ };
针对每个共享内存字典,ngx_lua 对其设置了上下文信息
typedef struct { ngx_rbtree_t rbtree; /* 整棵红黑树的根节点 */ ngx_rbtree_node_t sentinel; /* 哨兵节点 */ ngx_queue_t lru_queue; /* LRU 队列的哨兵节点 */ } ngx_http_lua_shdict_shctx_t; /* ctx in the shared memory */ typedef struct { ngx_http_lua_shdict_shctx_t *sh; ngx_slab_pool_t *shpool; /* slab 分配器 */ ngx_str_t name; /* 共享内存名 */ ngx_http_lua_main_conf_t *main_conf; ngx_log_t *log; /* log 对象 */ } ngx_http_lua_shdict_ctx_t;
这两个结构体是为了维护一整块共享内存字典而设计的.
而 ngx_http_lua_shm_zone_t 则是面向于维护共享内存本身的结构
typedef struct { ngx_log_t *log; ngx_http_lua_main_conf_t *lmcf; ngx_cycle_t *cycle; ngx_shm_zone_t zone; /* 指向的共享内存对象 */ } ngx_http_lua_shm_zone_ctx_t;
Zone Initialize
lua_shared_dict
指令可以添加一块共享内存字典,下面来分析下这条指令的回调解析函数 ngx_http_lua_shared_dict
.
char * ngx_http_lua_shared_dict(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_lua_main_conf_t *lmcf = conf; ngx_str_t *value, name; ngx_shm_zone_t *zone; ngx_shm_zone_t **zp; ngx_http_lua_shdict_ctx_t *ctx; ssize_t size; /* 每一块共享内存字典都被串联在这个 shdict_zones 数组里 */ if (lmcf->shdict_zones == NULL) { lmcf->shdict_zones = ngx_palloc(cf->pool, sizeof(ngx_array_t)); if (lmcf->shdict_zones == NULL) { return NGX_CONF_ERROR; } if (ngx_array_init(lmcf->shdict_zones, cf->pool, 2, sizeof(ngx_shm_zone_t *)) != NGX_OK) { return NGX_CONF_ERROR; } } value = cf->args->elts; ctx = NULL; if (value[1].len == 0) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid lua shared dict name \"%V\"", &value[1]); return NGX_CONF_ERROR; } name = value[1]; size = ngx_parse_size(&value[2]); /* 最小是 8k */ if (size <= 8191) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid lua shared dict size \"%V\"", &value[2]); return NGX_CONF_ERROR; } /* 创建上下文结构体 */ ctx = ngx_pcalloc(cf->pool, sizeof(ngx_http_lua_shdict_ctx_t)); if (ctx == NULL) { return NGX_CONF_ERROR; } ctx->name = name; ctx->main_conf = lmcf; ctx->log = &cf->cycle->new_log; /* 调用封装了 ngx_http_shared_memory_add 的方法 */ zone = ngx_http_lua_shared_memory_add(cf, &name, (size_t) size, &ngx_http_lua_module); if (zone == NULL) { return NGX_CONF_ERROR; } if (zone->data) { ctx = zone->data; ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "lua_shared_dict \"%V\" is already defined as " "\"%V\"", &name, &ctx->name); return NGX_CONF_ERROR; } /* 设置好初始化函数和参数 */ zone->init = ngx_http_lua_shdict_init_zone; zone->data = ctx; zp = ngx_array_push(lmcf->shdict_zones); if (zp == NULL) { return NGX_CONF_ERROR; } *zp = zone; lmcf->requires_shm = 1; return NGX_CONF_OK; }
这个函数功能比较简单,主要工作就是解析出当前添加的共享内存的名字和大小,然后将其挂到 ngx_lua
模块 main 配置文件下的 shdict_zones
数组上. 我们知道共享内存最终是通过 ngx_cycle_t
的 shared_memory
数组维护的,而这里调用了 ngx_http_lua_shared_memory_add
,这个函数则封装了 Nginx 原生的 ngx_http_shared_memory_add
接口.
ngx_http_lua_shared_memory_add
ngx_shm_zone_t * ngx_http_lua_shared_memory_add(ngx_conf_t *cf, ngx_str_t *name, size_t size, void *tag) { ...... /* 调用原生的接口添加一块共享内存,tag 则是 ngx_http_lua_module 模块结构的地址,这是 Nginx 的老技巧了 */ zone = ngx_shared_memory_add(cf, name, (size_t) size, tag); if (zone == NULL) { return NULL; } /* 说明对应共享内存已经存在 */ if (zone->data) { ctx = (ngx_http_lua_shm_zone_ctx_t *) zone->data; return &ctx->zone; } n = sizeof(ngx_http_lua_shm_zone_ctx_t); ctx = ngx_pcalloc(cf->pool, n); if (ctx == NULL) { return NULL; } ctx->lmcf = lmcf; ctx->log = &cf->cycle->new_log; ctx->cycle = cf->cycle; ngx_memcpy(&ctx->zone, zone, sizeof(ngx_shm_zone_t)); /* main conf 里同样维护了一个 ngx_http_lua_zone_ctx_t 的数组 */ zp = ngx_array_push(lmcf->shm_zones); if (zp == NULL) { return NULL; } *zp = zone; /* set zone init */ zone->init = ngx_http_lua_shared_memory_init; zone->data = ctx; lmcf->requires_shm = 1; return &ctx->zone; }
ngx_http_lua_shared_memory_add
函数里我们看到了共享内存初始化的函数,即 ngx_http_lua_shared_memory_init
,这个函数将在 ngx_init_cycle
里被调用.
ngx_http_lua_shared_memory_init
static ngx_int_t ngx_http_lua_shared_memory_init(ngx_shm_zone_t *shm_zone, void *data) { ...... ctx = (ngx_http_lua_shm_zone_ctx_t *) shm_zone->data; zone = &ctx->zone; odata = NULL; /* reload */ if (octx) { ozone = &octx->zone; odata = ozone->data; } zone->shm = shm_zone->shm; #if defined(nginx_version) && nginx_version >= 1009000 zone->noreuse = shm_zone->noreuse; #endif /* 这里的 init 方法实际上就是 ngx_http_lua_shdict_init_zone */ if (zone->init(zone, odata) != NGX_OK) { return NGX_ERROR; } ...... return NGX_OK; }
这个函数简介调用了 ngx_http_lua_shm_dict_init
,也就是站在共享内存字典的角度上进行初始化,所以才有了 ngx_http_lua_shared_memory_add
函数里对分配出来的 zone 结构进行的复制,一个由 ngx_cycle_t
维护,而另外一个存在于 ngx_http_lua_shm_zone_t
,二者的初始化方式不同.
ngx_http_lua_shdict_init_zone
ngx_int_t ngx_http_lua_shdict_init_zone(ngx_shm_zone_t *shm_zone, void *data) { ngx_http_lua_shdict_ctx_t *octx = data; size_t len; ngx_http_lua_shdict_ctx_t *ctx; dd("init zone"); ctx = shm_zone->data; /* reload */ if (octx) { ctx->sh = octx->sh; ctx->shpool = octx->shpool; return NGX_OK; } /* slab 管理器存放在整块共享内存的最前面 */ ctx->shpool = (ngx_slab_pool_t *) shm_zone->shm.addr; if (shm_zone->shm.exists) { ctx->sh = ctx->shpool->data; return NGX_OK; } ctx->sh = ngx_slab_alloc(ctx->shpool, sizeof(ngx_http_lua_shdict_shctx_t)); if (ctx->sh == NULL) { return NGX_ERROR; } /* * slab 的 data 成员用法通常是由模块自己决定的, * 这里用来存放 ngx_http_lua_shm_dict_shctx_t */ ctx->shpool->data = ctx->sh; /* 初始化红黑树和 LRU 队列 */ ngx_rbtree_init(&ctx->sh->rbtree, &ctx->sh->sentinel, ngx_http_lua_shdict_rbtree_insert_value); ngx_queue_init(&ctx->sh->lru_queue); len = sizeof(" in lua_shared_dict zone \"\"") + shm_zone->shm.name.len; ctx->shpool->log_ctx = ngx_slab_alloc(ctx->shpool, len); if (ctx->shpool->log_ctx == NULL) { return NGX_ERROR; } ngx_sprintf(ctx->shpool->log_ctx, " in lua_shared_dict zone \"%V\"%Z", &shm_zone->shm.name); #if defined(nginx_version) && nginx_version >= 1005013 ctx->shpool->log_nomem = 0; #endif return NGX_OK; } ``` 这个函数完成了共享内存字典的初始化,主要是红黑树和 LRU 队列的初始化. ### API Inject `ngx_http_lua_inject_shdict_api` 函数将 API 注入到各个对应的共享内存字典. ```c void ngx_http_lua_inject_shdict_api(ngx_http_lua_main_conf_t *lmcf, lua_State *L) { ngx_http_lua_shdict_ctx_t *ctx; ngx_uint_t i; ngx_shm_zone_t **zone; if (lmcf->shdict_zones != NULL) { lua_createtable(L, 0, lmcf->shdict_zones->nelts /* nrec */); /* ngx.shared */ /* 事实上所有的 API 都存放在一个新建的表,这个表将作为所有共享内存字典的元表 */ lua_createtable(L, 0 /* narr */, 18 /* nrec */); /* shared mt */ lua_pushcfunction(L, ngx_http_lua_shdict_get); lua_setfield(L, -2, "get"); /* 此处注入其他的 API */ lua_pushvalue(L, -1); /* shared mt mt */ lua_setfield(L, -2, "__index"); /* shared mt */ zone = lmcf->shdict_zones->elts; for (i = 0; i < lmcf->shdict_zones->nelts; i++) { ctx = zone[i]->data; lua_pushlstring(L, (char *) ctx->name.data, ctx->name.len); /* shared mt key */ /* 创建出每个共享内存对应的共享内存字典,也就是一张 Lua table */ lua_createtable(L, 1 /* narr */, 0 /* nrec */); /* table of zone[i] */ lua_pushlightuserdata(L, zone[i]); /* shared mt key ud */ /* 这里将每个共享内存字典对应的 ngx_http_lua_shm_zone_ctx_t 存放在新建的表数组部分,为了后续使用的 API 函数里可以方便拿到这个结构 */ lua_rawseti(L, -2, SHDICT_USERDATA_INDEX); /* {zone[i]} */ lua_pushvalue(L, -3); /* shared mt key ud mt */ lua_setmetatable(L, -2); /* shared mt key ud */ lua_rawset(L, -4); /* shared mt */ } lua_pop(L, 1); /* shared */ } else { lua_newtable(L); /* ngx.shared */ } lua_setfield(L, -2, "shared"); }
该函数将共享内存字典和 API 注入到 ngx.shared 表里,涉及到一些 Lua 和 C 的交互,建议读者拿纸和笔模拟下 Lua 栈的变化.
Normal API
初始化结束后,我们便可以在 Lua 代码里使用这些 API 了,在 ngx_lua 0.10.6
以前,还没有模拟 list 的操作,这里先来介绍下这些常规的 API.
ngx.shared.DICT.set
ngx.shared.DICT.add
ngx.shared.DICT.safe_set
ngx.shared.DICT.replace
ngx.shared.DICT.delete
ngx.shared.DICT.safe_add
这 6 个 API 是向共享内存字典里设置数据.
static int ngx_http_lua_shdict_add(lua_State *L) { return ngx_http_lua_shdict_set_helper(L, NGX_HTTP_LUA_SHDICT_ADD); } static int ngx_http_lua_shdict_safe_add(lua_State *L) { return ngx_http_lua_shdict_set_helper(L, NGX_HTTP_LUA_SHDICT_ADD |NGX_HTTP_LUA_SHDICT_SAFE_STORE); } static int ngx_http_lua_shdict_replace(lua_State *L) { return ngx_http_lua_shdict_set_helper(L, NGX_HTTP_LUA_SHDICT_REPLACE); } static int ngx_http_lua_shdict_set(lua_State *L) { return ngx_http_lua_shdict_set_helper(L, 0); } static int ngx_http_lua_shdict_safe_set(lua_State *L) { return ngx_http_lua_shdict_set_helper(L, NGX_HTTP_LUA_SHDICT_SAFE_STORE); } static int ngx_http_lua_shdict_delete(lua_State *L) { int n; n = lua_gettop(L); if (n != 2) { return luaL_error(L, "expecting 2 arguments, " "but only seen %d", n); } lua_pushnil(L); return ngx_http_lua_shdict_set_helper(L, 0); }
从上面的代码可以看到,这 6 个 API 都依赖于一个核心函数 ngx_http_lua_shdict_set_helper
,通过参数来影响 ngx_http_lua_shdict_set_helper
函数行为.
static int ngx_http_lua_shdict_set_helper(lua_State *L, int flags) { int i, n; ngx_str_t key; uint32_t hash; ngx_int_t rc; ngx_http_lua_shdict_ctx_t *ctx; ngx_http_lua_shdict_node_t *sd; ngx_str_t value; int value_type; double num; u_char c; lua_Number exptime = 0; u_char *p; ngx_rbtree_node_t *node; ngx_time_t *tp; ngx_shm_zone_t *zone; int forcible = 0; /* indicates whether to foricibly override other * valid entries */ int32_t user_flags = 0; ngx_queue_t *queue, *q; n = lua_gettop(L); if (n != 3 && n != 4 && n != 5) { return luaL_error(L, "expecting 3, 4 or 5 arguments, " "but only seen %d", n); } if (lua_type(L, 1) != LUA_TTABLE) { return luaL_error(L, "bad \"zone\" argument"); } /* 还记得上文讲到 API 注入的过程吗?每个共享内存字典的上下文保存在 * 充当字典的那张表里(ngx.shared.dog) */ zone = ngx_http_lua_shdict_get_zone(L, 1); if (zone == NULL) { return luaL_error(L, "bad \"zone\" argument"); } ctx = zone->data; if (lua_isnil(L, 2)) { lua_pushnil(L); lua_pushliteral(L, "nil key"); return 2; } key.data = (u_char *) luaL_checklstring(L, 2, &key.len); if (key.len == 0) { lua_pushnil(L); lua_pushliteral(L, "empty key"); return 2; } if (key.len > 65535) { lua_pushnil(L); lua_pushliteral(L, "key too long"); return 2; } /* 根据 crc 循环冗余计算出来的 hash 值用在红黑树节点之间的对比上 */ hash = ngx_crc32_short(key.data, key.len); value_type = lua_type(L, 3); /* 校验值类型 */ switch (value_type) { case SHDICT_TSTRING: value.data = (u_char *) lua_tolstring(L, 3, &value.len); break; case SHDICT_TNUMBER: value.len = sizeof(double); num = lua_tonumber(L, 3); value.data = (u_char *) # break; case SHDICT_TBOOLEAN: value.len = sizeof(u_char); c = lua_toboolean(L, 3) ? 1 : 0; value.data = &c; break; /* 比如 ngx.shared.DICT.delete */ case LUA_TNIL: if (flags & (NGX_HTTP_LUA_SHDICT_ADD|NGX_HTTP_LUA_SHDICT_REPLACE)) { lua_pushnil(L); lua_pushliteral(L, "attempt to add or replace nil values"); return 2; } ngx_str_null(&value); break; default: lua_pushnil(L); lua_pushliteral(L, "bad value type"); return 2; } if (n >= 4) { exptime = luaL_checknumber(L, 4); if (exptime < 0) { return luaL_error(L, "bad \"exptime\" argument"); } } if (n == 5) { user_flags = (uint32_t) luaL_checkinteger(L, 5); } /* 以阻塞进程的方式获取锁 */ ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 /* * 淘汰一些节点,第二个参数 n = 1 时则严格根据过期时间淘汰 1~2 个节点, * n = 0 时会强行淘汰最近最久未使用的节点,然后再根据过期时间淘汰 1~2 个节点 */ ngx_http_lua_shdict_expire(ctx, 1); #endif /* * 寻找 key 对应的节点 * 返回值 NGX_DONE 表示节点不存在 * NGX_DECLINED 表示节点存在但是已经过期 * NGX_OK 表示节点存在且未过期 */ rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returned %d", (int) rc); /* ngx.shared.dog:replace 方法 */ if (flags & NGX_HTTP_LUA_SHDICT_REPLACE) { /* 当节点不存在或者已经过期,直接返回 false 和 "not found",显然 forcible 是 0 */ if (rc == NGX_DECLINED || rc == NGX_DONE) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "not found"); lua_pushboolean(L, forcible); return 3; } /* rc == NGX_OK */ goto replace; } /* ngx.shared.dog:add */ if (flags & NGX_HTTP_LUA_SHDICT_ADD) { /* 当节点存在且没过期,返回 false 和 exists,这会 replace 刚好相反 */ if (rc == NGX_OK) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "exists"); lua_pushboolean(L, forcible); return 3; } if (rc == NGX_DONE) { /* exists but expired */ dd("go to replace"); goto replace; } /* rc == NGX_DECLINED */ dd("go to insert"); goto insert; } if (rc == NGX_OK || rc == NGX_DONE) { /* * 如果值为 nil,则删除节点 * 其他 API 的情况,先尝试在原来节点的基础上替代 * 无法替代,则删除节点,再插入节点 */ if (value_type == LUA_TNIL) { goto remove; } replace: /* 当值的长度一样,可以直接复用结构,提高效率,当然当值是 list 的时候要排除 */ if (value.data && value.len == (size_t) sd->value_len && sd->value_type != SHDICT_TLIST) { ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict set: found old entry and value " "size matched, reusing it"); /* 把节点移动到队首,因为刚刚访问过 */ ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); sd->key_len = (u_short) key.len; /* 设置好过期时间,0 则是永远不过期 */ if (exptime > 0) { tp = ngx_timeofday(); sd->expires = (uint64_t) tp->sec * 1000 + tp->msec + (uint64_t) (exptime * 1000); } else { sd->expires = 0; } sd->user_flags = user_flags; sd->value_len = (uint32_t) value.len; dd("setting value type to %d", value_type); sd->value_type = (uint8_t) value_type; p = ngx_copy(sd->data, key.data, key.len); ngx_memcpy(p, value.data, value.len); ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 1); lua_pushnil(L); lua_pushboolean(L, forcible); return 3; } ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict set: found old entry but value size " "NOT matched, removing it first"); remove: /* list 情况比较特殊,因为此时值存放的是这个 list 的哨兵节点,需要遍历列表,删除所有元素,对 queue 不清楚的读者可以取阅读 ngx_queue_t 的相关的实现 */ if (sd->value_type == SHDICT_TLIST) { queue = ngx_http_lua_shdict_get_list_head(sd, key.len); for (q = ngx_queue_head(queue); q != ngx_queue_sentinel(queue); q = ngx_queue_next(q)) { p = (u_char *) ngx_queue_data(q, ngx_http_lua_shdict_list_node_t, queue); ngx_slab_free_locked(ctx->shpool, p); } } /* 从 LRU 队列和红黑树上删除节点 */ ngx_queue_remove(&sd->queue); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); /* 当然需要让 slab 管理器回收内存 */ ngx_slab_free_locked(ctx->shpool, node); } insert: /* rc == NGX_DECLINED or value size unmatch */ /* value 为 nil 等于不需要插入操作 */ if (value.data == NULL) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 1); lua_pushnil(L); lua_pushboolean(L, 0); return 3; } ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict set: creating a new entry"); /* * 这些结构都是存放在一块连续内存里的,大小则是一个红黑树节点的大小 * 外加一个 ngx_http_lua_shdict_node_t 的大小,外加键和值的长度 */ n = offsetof(ngx_rbtree_node_t, color) + offsetof(ngx_http_lua_shdict_node_t, data) + key.len + value.len; dd("overhead = %d", (int) (offsetof(ngx_rbtree_node_t, color) + offsetof(ngx_http_lua_shdict_node_t, data))); node = ngx_slab_alloc_locked(ctx->shpool, n); if (node == NULL) { /* * 当共享内存不够的时候,考虑下 flag 标志, * 如果是安全操作(safe_add 或者 safe_set),则直接返回 */ if (flags & NGX_HTTP_LUA_SHDICT_SAFE_STORE) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "no memory"); return 2; } ngx_log_debug1(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict set: overriding non-expired items " "due to memory shortage for entry \"%V\"", &key); /* 否则尝试淘汰一些节点再插入 */ for (i = 0; i < 30; i++) { /* 上文说过,n = 0 会强行淘汰一个节点 */ if (ngx_http_lua_shdict_expire(ctx, 0) == 0) { /* 实际上就是节点都被清空的情况 */ break; } forcible = 1; node = ngx_slab_alloc_locked(ctx->shpool, n); if (node != NULL) { goto allocated; } } ngx_shmtx_unlock(&ctx->shpool->mutex); /* 经过强行淘汰还是分配失败,直接返回 */ lua_pushboolean(L, 0); lua_pushliteral(L, "no memory"); lua_pushboolean(L, forcible); return 3; } allocated: /* 紧接着 ngx_rbtree_node_t */ sd = (ngx_http_lua_shdict_node_t *) &node->color; node->key = hash; sd->key_len = (u_short) key.len; if (exptime > 0) { tp = ngx_timeofday(); sd->expires = (uint64_t) tp->sec * 1000 + tp->msec + (uint64_t) (exptime * 1000); } else { sd->expires = 0; } sd->user_flags = user_flags; sd->value_len = (uint32_t) value.len; dd("setting value type to %d", value_type); sd->value_type = (uint8_t) value_type; /* key 存放在 sd->data 指向的内存 */ p = ngx_copy(sd->data, key.data, key.len); /* value 则紧紧存放在 key 后面 */ ngx_memcpy(p, value.data, value.len); /* 插入到红黑树和 LRU 队列 */ ngx_rbtree_insert(&ctx->sh->rbtree, node); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 1); lua_pushnil(L); lua_pushboolean(L, forcible); return 3; }
ngx_http_lua_shdict_set_helper
函数是插入操作的核心,它总共考虑了 5 种不同的情况,根据不同的需求做出不同的操作. 不论是 set
也好, add
也好,亦或是 safe_set
等等,其操作核心思路都是一致的:在已有的红黑树上遍历,如果找到,则如何操作(可以复用则复用,无法复用则先删除);如果没找到,需要创建新节点,创建新节点的时候如果内存不够,进行淘汰,新节点创建完成并且初始化后,插入到红黑树上,挂到 LRU 队列的首部.
ngx.shared.DICT.get
ngx.shared.DICT.get_stale
这两个函数内部最核心的函数则是 ngx_http_lua_shdict_get_helper
static int ngx_http_lua_shdict_get_helper(lua_State *L, int get_stale) { ...... ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 if (!get_stale) { /* 如果是 ngx.shared.DICT.get 操作,先尝试过期 1~2 个节点 */ ngx_http_lua_shdict_expire(ctx, 1); } #endif rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returns %d", (int) rc); /* 节点没找到,或者节点已经过期但是操作是 ngx.shared.DICT.get,直接 return nil */ if (rc == NGX_DECLINED || (rc == NGX_DONE && !get_stale)) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); return 1; } /* rc == NGX_OK || (rc == NGX_DONE && get_stale) */ value_type = sd->value_type; dd("data: %p", sd->data); dd("key len: %d", (int) sd->key_len); /* 取出 value */ value.data = sd->data + sd->key_len; value.len = (size_t) sd->value_len; switch (value_type) { case SHDICT_TSTRING: lua_pushlstring(L, (char *) value.data, value.len); break; case SHDICT_TNUMBER: if (value.len != sizeof(double)) { ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad lua number value size found for key %s " "in shared_dict %s: %lu", key.data, name.data, (unsigned long) value.len); } ngx_memcpy(&num, value.data, sizeof(double)); lua_pushnumber(L, num); break; case SHDICT_TBOOLEAN: if (value.len != sizeof(u_char)) { ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad lua boolean value size found for key %s " "in shared_dict %s: %lu", key.data, name.data, (unsigned long) value.len); } c = *value.data; lua_pushboolean(L, c ? 1 : 0); break; /* list 有自己的一套操作,不允许使用 ngx.shared.DICT.get 和 ngx.shared.DICT.get_stale */ case SHDICT_TLIST: ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "value is a list"); return 2; default: /* 其他情况抛出异常 */ ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad value type found for key %s in " "shared_dict %s: %d", key.data, name.data, value_type); } user_flags = sd->user_flags; ngx_shmtx_unlock(&ctx->shpool->mutex); if (get_stale) { /* always return value, flags, stale */ if (user_flags) { lua_pushinteger(L, (lua_Integer) user_flags); } else { lua_pushnil(L); } lua_pushboolean(L, rc == NGX_DONE); return 3; } if (user_flags) { lua_pushinteger(L, (lua_Integer) user_flags); return 2; } return 1; }
这个函数总体来讲非常简单,只要针对是否能读取过期数据进行判断即可,具体读者可以参阅注释.
ngx.shared.DICT.inrc
ngx.shared.DICT.get_keys
ngx.shared.DICT.flush_all
ngx.shared.DICT.flush_expire
这四个 API 实现也十分简单,具体请看下面的注释.
static int ngx_http_lua_shdict_incr(lua_State *L) { ...... if (n == 4) { init = luaL_checknumber(L, 4); } dd("looking up key %.*s in shared dict %.*s", (int) key.len, key.data, (int) ctx->name.len, ctx->name.data); ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 ngx_http_lua_shdict_expire(ctx, 1); #endif rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returned %d", (int) rc); /* 节点不存在或者过期*/ if (rc == NGX_DECLINED || rc == NGX_DONE) { /* 没有携带 init 参数 */ if (n == 3) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "not found"); return 2; } /* add value */ num = value + init; /* 过期 */ if (rc == NGX_DONE) { /* found an expired item */ /* 该过期节点原本存放的值类型就是数值 */ if ((size_t) sd->value_len == sizeof(double) && sd->value_type != SHDICT_TLIST) { ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict incr: found old entry and " "value size matched, reusing it"); ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); dd("go to setvalue"); /* 设置值 */ goto setvalue; } dd("go to remove"); goto remove; } dd("go to insert"); goto insert; } /* rc == NGX_OK */ /* 节点没过期,然而原本值不是数值 */ if (sd->value_type != SHDICT_TNUMBER || sd->value_len != sizeof(double)) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "not a number"); return 2; } ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); dd("setting value type to %d", (int) sd->value_type); p = sd->data + key.len; ngx_memcpy(&num, p, sizeof(double)); num += value; ngx_memcpy(p, (double *) &num, sizeof(double)); ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, num); lua_pushnil(L); return 2; remove: ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict incr: found old entry but value size " "NOT matched, removing it first"); /* 原本值是列表则需要遍历列表删除节点 */ if (sd->value_type == SHDICT_TLIST) { queue = ngx_http_lua_shdict_get_list_head(sd, key.len); for (q = ngx_queue_head(queue); q != ngx_queue_sentinel(queue); q = ngx_queue_next(q)) { p = (u_char *) ngx_queue_data(q, ngx_http_lua_shdict_list_node_t, queue); ngx_slab_free_locked(ctx->shpool, p); } } ngx_queue_remove(&sd->queue); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); insert: ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict incr: creating a new entry"); n = offsetof(ngx_rbtree_node_t, color) + offsetof(ngx_http_lua_shdict_node_t, data) + key.len + sizeof(double); /* 分配一个节点 */ node = ngx_slab_alloc_locked(ctx->shpool, n); if (node == NULL) { ngx_log_debug1(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict incr: overriding non-expired items " "due to memory shortage for entry \"%V\"", &key); for (i = 0; i < 30; i++) { /* 无条件淘汰一个节点,再根据过期时间淘汰 1~2 个节点 */ if (ngx_http_lua_shdict_expire(ctx, 0) == 0) { break; } forcible = 1; node = ngx_slab_alloc_locked(ctx->shpool, n); if (node != NULL) { goto allocated; } } /* 内存不足 */ ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "no memory"); lua_pushboolean(L, forcible); return 3; } allocated: /* 设置好键和值 */ sd = (ngx_http_lua_shdict_node_t *) &node->color; node->key = hash; sd->key_len = (u_short) key.len; sd->value_len = (uint32_t) sizeof(double); ngx_rbtree_insert(&ctx->sh->rbtree, node); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); setvalue: sd->user_flags = 0; sd->expires = 0; /* 通过 incr 插入的节点,没有过期时间 */ dd("setting value type to %d", LUA_TNUMBER); sd->value_type = (uint8_t) LUA_TNUMBER; p = ngx_copy(sd->data, key.data, key.len); ngx_memcpy(p, (double *) &num, sizeof(double)); ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, num); lua_pushnil(L); lua_pushboolean(L, forcible); return 3; } static int ngx_http_lua_shdict_get_keys(lua_State *L) { ...... if (n == 2) { attempts = luaL_checkint(L, 2); } ctx = zone->data; ngx_shmtx_lock(&ctx->shpool->mutex); /* 空 */ if (ngx_queue_empty(&ctx->sh->lru_queue)) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_createtable(L, 0, 0); return 1; } tp = ngx_timeofday(); now = (uint64_t) tp->sec * 1000 + tp->msec; /* first run through: get total number of elements we need to allocate */ q = ngx_queue_last(&ctx->sh->lru_queue); while (q != ngx_queue_sentinel(&ctx->sh->lru_queue)) { prev = ngx_queue_prev(q); sd = ngx_queue_data(q, ngx_http_lua_shdict_node_t, queue); /* 挑出还没过期的 */ if (sd->expires == 0 || sd->expires > now) { total++; /* 至多拿 attemps 个 key */ if (attempts && total == attempts) { break; } } q = prev; } lua_createtable(L, total, 0); /* second run through: add keys to table */ total = 0; q = ngx_queue_last(&ctx->sh->lru_queue); while (q != ngx_queue_sentinel(&ctx->sh->lru_queue)) { prev = ngx_queue_prev(q); sd = ngx_queue_data(q, ngx_http_lua_shdict_node_t, queue); if (sd->expires == 0 || sd->expires > now) { lua_pushlstring(L, (char *) sd->data, sd->key_len); lua_rawseti(L, -2, ++total); if (attempts && total == attempts) { break; } } q = prev; } ngx_shmtx_unlock(&ctx->shpool->mutex); /* table is at top of stack */ return 1; } /* 把所有节点标记为过期 */ static int ngx_http_lua_shdict_flush_all(lua_State *L) { ...... ctx = zone->data; ngx_shmtx_lock(&ctx->shpool->mutex); for (q = ngx_queue_head(&ctx->sh->lru_queue); q != ngx_queue_sentinel(&ctx->sh->lru_queue); q = ngx_queue_next(q)) { sd = ngx_queue_data(q, ngx_http_lua_shdict_node_t, queue); sd->expires = 1; /* 设置成 1,后续比较时必然认为节点是过期的 */ } /* */ ngx_http_lua_shdict_expire(ctx, 0); ngx_shmtx_unlock(&ctx->shpool->mutex); return 0; } /* 将过期的节点移除 */ static int ngx_http_lua_shdict_flush_expired(lua_State *L) { ...... if (n == 2) { /* 至多删除 attempts 个过期节点 */ attempts = luaL_checkint(L, 2); } ctx = zone->data; ngx_shmtx_lock(&ctx->shpool->mutex); if (ngx_queue_empty(&ctx->sh->lru_queue)) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, 0); return 1; } tp = ngx_timeofday(); now = (uint64_t) tp->sec * 1000 + tp->msec; q = ngx_queue_last(&ctx->sh->lru_queue); while (q != ngx_queue_sentinel(&ctx->sh->lru_queue)) { prev = ngx_queue_prev(q); sd = ngx_queue_data(q, ngx_http_lua_shdict_node_t, queue); if (sd->expires != 0 && sd->expires <= now) { /* 同样地,list 需要遍历每个元素 */ if (sd->value_type == SHDICT_TLIST) { list_queue = ngx_http_lua_shdict_get_list_head(sd, sd->key_len); for (lq = ngx_queue_head(list_queue); lq != ngx_queue_sentinel(list_queue); lq = ngx_queue_next(lq)) { lnode = ngx_queue_data(lq, ngx_http_lua_shdict_list_node_t, queue); ngx_slab_free_locked(ctx->shpool, lnode); } } ngx_queue_remove(q); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); freed++; if (attempts && freed == attempts) { break; } } q = prev; } ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, freed); return 1; }
List API
ngx_lua
0.10.6
版本开始,共享内存字典上可以使用双端队列,这些操作类似于 redis
,进一步提升了开发的灵活性,其设计原理是,内部值的类型标记为 list,同样存放在红黑树上,其他 list 上的元素也是通过 ngx_queue_t
组织,哨兵节点就和上一节所述的普通的 API 一致,存放在值所存放的内存位置(键的后面),每个 list 上的元素都用一个 ngx_http_lua_shdict_list_node_t
描述.
typedef struct { ngx_queue_t queue; /* 双端队列上的位置 */ uint32_t value_len; /* 值长度*/ uint8_t value_type; /* 值类型 */ u_char data[1]; /* 值的首地址 */ } ngx_http_lua_shdict_list_node_t;
提供的 API 则有:
- lpop
- rpop
- lpush
- rpush
- llen
下面对这些 API 进行分析.
ngx.shared.DICT.lpop
ngx.shared.DICT.rpop
同样的套路,这两个 API 的核心函数则是 ngx_http_lua_shdict_pop_helper
static int ngx_http_lua_shdict_pop_helper(lua_State *L, int flags) { ...... hash = ngx_crc32_short(key.data, key.len); ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 /* 同样地,先尝试过期 1~2 节点 */ ngx_http_lua_shdict_expire(ctx, 1); #endif rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returned %d", (int) rc); /* 不存在或者过期 */ if (rc == NGX_DECLINED || rc == NGX_DONE) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); return 1; } /* rc == NGX_OK */ /* 节点虽然存在,但是对应的不是 list,返回 nil 和错误串 */ if (sd->value_type != SHDICT_TLIST) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "value not a list"); return 2; } if (sd->value_len <= 0) { ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad lua list length found for key %s " "in shared_dict %s: %lu", key.data, name.data, (unsigned long) sd->value_len); } /* 取出哨兵节点 */ queue = ngx_http_lua_shdict_get_list_head(sd, key.len); /* lpop */ if (flags == NGX_HTTP_LUA_SHDICT_LEFT) { queue = ngx_queue_head(queue); /* rpop */ } else { queue = ngx_queue_last(queue); } lnode = ngx_queue_data(queue, ngx_http_lua_shdict_list_node_t, queue); value_type = lnode->value_type; dd("data: %p", lnode->data); dd("value len: %d", (int) sd->value_len); value.data = lnode->data; value.len = (size_t) lnode->value_len; switch (value_type) { case SHDICT_TSTRING: /* 返回字符串 */ lua_pushlstring(L, (char *) value.data, value.len); break; case SHDICT_TNUMBER: /* 返回数值 */ if (value.len != sizeof(double)) { ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad lua list node number value size found " "for key %s in shared_dict %s: %lu", key.data, name.data, (unsigned long) value.len); } ngx_memcpy(&num, value.data, sizeof(double)); lua_pushnumber(L, num); break; default: ngx_shmtx_unlock(&ctx->shpool->mutex); return luaL_error(L, "bad list node value type found for key %s in " "shared_dict %s: %d", key.data, name.data, value_type); } /* 从 list 里移除 */ ngx_queue_remove(queue); ngx_slab_free_locked(ctx->shpool, lnode); /* 事实上,当共享内存字典值是 list 的时候,这个 sd->value_len 被拿来存放 list 的元素个数,等于 1 表示整个 list 空了,需要释放哨兵节点 */ if (sd->value_len == 1) { ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict list: empty node after pop, " "remove it"); ngx_queue_remove(&sd->queue); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); } else { /* sd->value_len-- */ sd->value_len = sd->value_len - 1; /* 移动到 LRU 队列队首,刚刚访问过 */ ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); } ngx_shmtx_unlock(&ctx->shpool->mutex); return 1; }
整个函数也比较简单,整体思路就是取出 list 的哨兵节点,根据是 lpop 还是 rpop 进行节点移除即可.
lpush 和 rpush 的核心函数则是 ngx_http_lua_shdict_push_helper
static int ngx_http_lua_shdict_push_helper(lua_State *L, int flags) { ...... value_type = lua_type(L, 3); switch (value_type) { case SHDICT_TSTRING: value.data = (u_char *) lua_tolstring(L, 3, &value.len); break; case SHDICT_TNUMBER: value.len = sizeof(double); num = lua_tonumber(L, 3); value.data = (u_char *) # break; default: lua_pushnil(L); lua_pushliteral(L, "bad value type"); return 2; } ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 ngx_http_lua_shdict_expire(ctx, 1); #endif rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returned %d", (int) rc); /* exists but expired */ if (rc == NGX_DONE) { if (sd->value_type != SHDICT_TLIST) { /* TODO: reuse when length matched */ /* 过期,值类型不是 list,则先移除 */ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict push: found old entry and value " "type not matched, remove it first"); ngx_queue_remove(&sd->queue); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); dd("go to init_list"); goto init_list; } /* 节点过期,值是 list */ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict push: found old entry and value " "type matched, reusing it"); sd->expires = 0; /* free list nodes */ queue = ngx_http_lua_shdict_get_list_head(sd, key.len); for (q = ngx_queue_head(queue); q != ngx_queue_sentinel(queue); q = ngx_queue_next(q)) { /* TODO: reuse matched size list node */ /* 移除之前所有的节点 */ lnode = ngx_queue_data(q, ngx_http_lua_shdict_list_node_t, queue); ngx_slab_free_locked(ctx->shpool, lnode); } ngx_queue_init(queue); ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); dd("go to push_node"); goto push_node; } /* exists and not expired */ if (rc == NGX_OK) { /* 不是 list */ if (sd->value_type != SHDICT_TLIST) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "value not a list"); return 2; } queue = ngx_http_lua_shdict_get_list_head(sd, key.len); ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); dd("go to push_node"); goto push_node; } /* rc == NGX_DECLINED, not found */ init_list: /* 分配一个节点 */ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict list: creating a new entry"); /* NOTICE: we assume the begin point aligned in slab, be careful */ n = offsetof(ngx_rbtree_node_t, color) + offsetof(ngx_http_lua_shdict_node_t, data) + key.len + sizeof(ngx_queue_t); dd("length before aligned: %d", n); n = (int) (uintptr_t) ngx_align_ptr(n, NGX_ALIGNMENT); dd("length after aligned: %d", n); node = ngx_slab_alloc_locked(ctx->shpool, n); if (node == NULL) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "no memory"); return 2; } sd = (ngx_http_lua_shdict_node_t *) &node->color; queue = ngx_http_lua_shdict_get_list_head(sd, key.len); node->key = hash; sd->key_len = (u_short) key.len; sd->expires = 0; sd->value_len = 0; /* 当前队列是空 */ dd("setting value type to %d", (int) SHDICT_TLIST); sd->value_type = (uint8_t) SHDICT_TLIST; ngx_memcpy(sd->data, key.data, key.len); ngx_queue_init(queue); ngx_rbtree_insert(&ctx->sh->rbtree, node); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); push_node: /* 推入一个节点 */ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict list: creating a new list node"); n = offsetof(ngx_http_lua_shdict_list_node_t, data) + value.len; dd("list node length: %d", n); lnode = ngx_slab_alloc_locked(ctx->shpool, n); if (lnode == NULL) { if (sd->value_len == 0) { ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ctx->log, 0, "lua shared dict list: no memory for create" " list node and list empty, remove it"); /* 分配失败,list 空的时候把整个节点都删除 */ ngx_queue_remove(&sd->queue); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); } ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushboolean(L, 0); lua_pushliteral(L, "no memory"); return 2; } dd("setting list length to %d", sd->value_len + 1); sd->value_len = sd->value_len + 1; dd("setting list node value length to %d", (int) value.len); lnode->value_len = (uint32_t) value.len; dd("setting list node value type to %d", value_type); lnode->value_type = (uint8_t) value_type; ngx_memcpy(lnode->data, value.data, value.len); /* lpush */ if (flags == NGX_HTTP_LUA_SHDICT_LEFT) { ngx_queue_insert_head(queue, &lnode->queue); } else { /* rpush */ ngx_queue_insert_tail(queue, &lnode->queue); } ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, sd->value_len); return 1; }
这个函数的流程也是先从目前的红黑树上找到节点,判断之前存放的是否过期,过期的时候,如果之前也是 list,则在移除所有的 list 元素后,复用节点,然后推入新元素;如果不是 list,则删除原来的节点,然后初始化 list、push 元素;如果不过期且原来不是 list,返回 nil
和错误串,否则直接在原来基础上 push 元素即可.
ngx.shared.DICT.llen
static int ngx_http_lua_shdict_llen(lua_State *L) { ...... hash = ngx_crc32_short(key.data, key.len); ngx_shmtx_lock(&ctx->shpool->mutex); #if 1 ngx_http_lua_shdict_expire(ctx, 1); #endif rc = ngx_http_lua_shdict_lookup(zone, hash, key.data, key.len, &sd); dd("shdict lookup returned %d", (int) rc); if (rc == NGX_OK) { /* 节点存在且不是 list */ if (sd->value_type != SHDICT_TLIST) { ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnil(L); lua_pushliteral(L, "value not a list"); return 2; } ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); ngx_shmtx_unlock(&ctx->shpool->mutex); /* sd->value_len 压栈 */ lua_pushnumber(L, (lua_Number) sd->value_len); return 1; } ngx_shmtx_unlock(&ctx->shpool->mutex); lua_pushnumber(L, 0); return 1; }
Auxiliary Function
上面介绍的这些函数,用到了一些辅助函数,有:
ngx_http_lua_shdict_get_zone
ngx_http_lua_shdict_expire
ngx_http_lua_shdict_get_list_head
ngx_http_lua_shdict_lookup
下面来对这些辅助函数进行下分析.
static ngx_inline ngx_shm_zone_t * ngx_http_lua_shdict_get_zone(lua_State *L, int index) { ngx_shm_zone_t *zone; /* * 记得上文讲 API 的 inject 的部分吗, * 每个共享内存字典的上下文结构体起始就放在提供给用户的 * Lua table 的数组部分 */ lua_rawgeti(L, index, SHDICT_USERDATA_INDEX); zone = lua_touserdata(L, -1); lua_pop(L, 1); return zone; } static int ngx_http_lua_shdict_expire(ngx_http_lua_shdict_ctx_t *ctx, ngx_uint_t n) { ngx_time_t *tp; uint64_t now; ngx_queue_t *q, *list_queue, *lq; int64_t ms; ngx_rbtree_node_t *node; ngx_http_lua_shdict_node_t *sd; int freed = 0; ngx_http_lua_shdict_list_node_t *lnode; tp = ngx_timeofday(); now = (uint64_t) tp->sec * 1000 + tp->msec; /* * n == 1 deletes one or two expired entries * n == 0 deletes oldest entry by force * and one or two zero rate entries */ while (n < 3) { /* 整个共享内存字典空了 */ if (ngx_queue_empty(&ctx->sh->lru_queue)) { return freed; } /* 队尾的节点是最近最久未使用的 */ q = ngx_queue_last(&ctx->sh->lru_queue); sd = ngx_queue_data(q, ngx_http_lua_shdict_node_t, queue); /* 参数 n 大于 0 */ if (n++ != 0) { /* 永不过期的节点 */ if (sd->expires == 0) { return freed; } ms = sd->expires - now; if (ms > 0) { /* 过期时间还没到 */ return freed; } } /* 如果参数 n 传入时为 0,则必然会淘汰一个节点 */ /* 对于 list 需要特殊处理,遍历整个 list,删除元素 */ if (sd->value_type == SHDICT_TLIST) { list_queue = ngx_http_lua_shdict_get_list_head(sd, sd->key_len); for (lq = ngx_queue_head(list_queue); lq != ngx_queue_sentinel(list_queue); lq = ngx_queue_next(lq)) { lnode = ngx_queue_data(lq, ngx_http_lua_shdict_list_node_t, queue); ngx_slab_free_locked(ctx->shpool, lnode); } } /* 删除节点 */ ngx_queue_remove(q); node = (ngx_rbtree_node_t *) ((u_char *) sd - offsetof(ngx_rbtree_node_t, color)); ngx_rbtree_delete(&ctx->sh->rbtree, node); ngx_slab_free_locked(ctx->shpool, node); freed++; } return freed; } static ngx_inline ngx_queue_t * ngx_http_lua_shdict_get_list_head(ngx_http_lua_shdict_node_t *sd, size_t len) { /* 其实就是把节点存放值的地址取出来(有对齐),转换成 ngx_queue_t 的类型 */ return (ngx_queue_t *) ngx_align_ptr(((u_char *) &sd->data + len), NGX_ALIGNMENT); } /* 检索节点 */ static ngx_int_t ngx_http_lua_shdict_lookup(ngx_shm_zone_t *shm_zone, ngx_uint_t hash, u_char *kdata, size_t klen, ngx_http_lua_shdict_node_t **sdp) { ngx_int_t rc; ngx_time_t *tp; uint64_t now; int64_t ms; ngx_rbtree_node_t *node, *sentinel; ngx_http_lua_shdict_ctx_t *ctx; ngx_http_lua_shdict_node_t *sd; ctx = shm_zone->data; node = ctx->sh->rbtree.root; sentinel = ctx->sh->rbtree.sentinel; while (node != sentinel) { if (hash < node->key) { /* 左子树 */ node = node->left; continue; } if (hash > node->key) { /* 右子树 */ node = node->right; continue; } /* hash == node->key */ sd = (ngx_http_lua_shdict_node_t *) &node->color; rc = ngx_memn2cmp(kdata, sd->data, klen, (size_t) sd->key_len); if (rc == 0) { /* HIT */ ngx_queue_remove(&sd->queue); ngx_queue_insert_head(&ctx->sh->lru_queue, &sd->queue); *sdp = sd; dd("node expires: %lld", (long long) sd->expires); if (sd->expires != 0) { /* 判断是否过期 */ tp = ngx_timeofday(); now = (uint64_t) tp->sec * 1000 + tp->msec; ms = sd->expires - now; dd("time to live: %lld", (long long) ms); if (ms < 0) { /* 过期 */ dd("node already expired"); return NGX_DONE; } } return NGX_OK; } node = (rc < 0) ? node->left : node->right; } *sdp = NULL; /* 没有找到 */ return NGX_DECLINED; }
以上所述就是小编给大家介绍的《lua-nginx-module 源码分析之共享内存字典》,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持!
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