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/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#include "proxy.h"
// No GC necessary.
struct mcp_ratelim_tbf {
uint32_t bucket;
uint32_t limit;
uint32_t fill_rate; // tokens to add per tick rate
uint32_t tick_rate; // in milliseconds
int64_t last_update; // time in milliseconds
};
struct mcp_ratelim_global_tbf {
struct mcp_globalobj_s g;
struct mcp_ratelim_tbf tbf;
};
#define TIMEVAL_TO_MILLIS(n) (n.tv_usec / 1000 + n.tv_sec * (uint64_t)1000)
// global config VM object GC
int mcplib_ratelim_global_tbf_gc(lua_State *L) {
struct mcp_ratelim_global_tbf *lim = luaL_checkudata(L, 1, "mcp.ratelim_global_tbf");
assert(lim->g.refcount == 0);
mcp_gobj_finalize(&lim->g);
// no other memory to directly free, just kill the mutex.
return 0;
}
// worker thread proxy object GC
int mcplib_ratelim_proxy_tbf_gc(lua_State *L) {
struct mcp_ratelim_global_tbf **lim_p = luaL_checkudata(L, 1, "mcp.ratelim_proxy_tbf");
struct mcp_ratelim_global_tbf *lim = *lim_p;
proxy_ctx_t *ctx = PROXY_GET_THR_CTX(L);
mcp_gobj_unref(ctx, &lim->g);
return 0;
}
int mcp_ratelim_proxy_tbf(lua_State *from, lua_State *to) {
// from, -3 should have the userdata.
struct mcp_ratelim_global_tbf *lim = luaL_checkudata(from, -3, "mcp.ratelim_global_tbf");
struct mcp_ratelim_global_tbf **lim_p = lua_newuserdatauv(to, sizeof(struct mcp_ratelim_global_tbf *), 0);
luaL_setmetatable(to, "mcp.ratelim_proxy_tbf");
*lim_p = lim;
lua_pushvalue(from, -3); // copy ratelim obj to ref below
mcp_gobj_ref(from, &lim->g); // pops obj copy
return 0;
}
static lua_Integer _tbf_check(lua_State *L, char *key) {
lua_Integer n = 0;
if (lua_getfield(L, 1, key) != LUA_TNIL) {
n = lua_tointeger(L, -1);
if (n < 0 || n > UINT_MAX-1) {
proxy_lua_error(L, "mcp.ratelim_tbf: arguments must be unsigned 32 bit integer");
}
}
lua_pop(L, 1); // pops value or nil.
return n;
}
static void _setup_tbf(lua_State *L, struct mcp_ratelim_tbf *lim) {
struct timeval now;
luaL_checktype(L, 1, LUA_TTABLE);
lim->limit = _tbf_check(L, "limit");
lim->fill_rate = _tbf_check(L, "fillrate");
lim->tick_rate = _tbf_check(L, "tickrate");
// seed the token bucket filter.
lim->bucket = lim->limit;
gettimeofday(&now, NULL);
lim->last_update = TIMEVAL_TO_MILLIS(now);
}
int mcplib_ratelim_tbf(lua_State *L) {
struct mcp_ratelim_tbf *lim = lua_newuserdatauv(L, sizeof(*lim), 0);
memset(lim, 0, sizeof(*lim));
luaL_setmetatable(L, "mcp.ratelim_tbf");
_setup_tbf(L, lim);
return 1;
}
int mcplib_ratelim_global_tbf(lua_State *L) {
struct mcp_ratelim_global_tbf *lim = lua_newuserdatauv(L, sizeof(*lim), 0);
memset(lim, 0, sizeof(*lim));
// TODO: during next refactor, add "globalobj init" phase, which probably
// just does this.
pthread_mutex_init(&lim->g.lock, NULL);
luaL_setmetatable(L, "mcp.ratelim_global_tbf");
_setup_tbf(L, &lim->tbf);
return 1;
}
static int _update_tbf(struct mcp_ratelim_tbf *lim, int take, uint64_t now) {
uint64_t delta = 0;
delta = now - lim->last_update;
if (delta > lim->tick_rate) {
// find how many ticks to add to the bucket.
uint32_t toadd = delta / lim->tick_rate;
// advance time up to the most recent tick.
lim->last_update += toadd * lim->tick_rate;
// add tokens to the bucket
lim->bucket += toadd * lim->fill_rate;
if (lim->bucket > lim->limit) {
lim->bucket = lim->limit;
}
}
if (lim->bucket > take) {
lim->bucket -= take;
return 1;
} else {
return 0;
}
}
int mcplib_ratelim_tbf_call(lua_State *L) {
struct mcp_ratelim_tbf *lim = luaL_checkudata(L, 1, "mcp.ratelim_tbf");
luaL_checktype(L, 2, LUA_TNUMBER);
int take = lua_tointeger(L, 2);
struct timeval now;
uint64_t now_millis = 0;
gettimeofday(&now, NULL);
now_millis = TIMEVAL_TO_MILLIS(now);
lua_pushboolean(L, _update_tbf(lim, take, now_millis));
return 1;
}
// NOTE: it should be possible to run a TBF using atomics, in the future when
// we start to support C11 atomics.
// Flip the concept of checking the time, updating, then subtracting the take
// to:
// - how much "time elapsed" is necessary for the take requested
// - atomically load the old time
// - if not enough time delta between old time and now, return false
// - else atomically swap the update time with the new time
// - compare and update the oldtime to newtime
// - not sure how much perf this buys you. would have to test.
int mcplib_ratelim_proxy_tbf_call(lua_State *L) {
struct mcp_ratelim_global_tbf **lim_p = luaL_checkudata(L, 1, "mcp.ratelim_proxy_tbf");
// line was kinda long / hard to read.
struct mcp_ratelim_global_tbf *lim = *lim_p;
struct timeval now;
luaL_checktype(L, 2, LUA_TNUMBER);
int take = lua_tointeger(L, 2);
gettimeofday(&now, NULL);
uint64_t now_millis = 0;
now_millis = TIMEVAL_TO_MILLIS(now);
pthread_mutex_lock(&lim->g.lock);
int res = _update_tbf(&lim->tbf, take, now_millis);
pthread_mutex_unlock(&lim->g.lock);
lua_pushboolean(L, res);
return 1;
}
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