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ngx_http_upstream_fair_module.c
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ngx_http_upstream_fair_module.c
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/*
* Copyright (C) 2007 Grzegorz Nosek
* Work sponsored by Ezra Zygmuntowicz & EngineYard.com
*
* Based on nginx source (C) Igor Sysoev
*/
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>
typedef struct {
ngx_uint_t nreq;
ngx_uint_t total_req;
ngx_uint_t last_req_id;
ngx_uint_t fails;
ngx_uint_t current_weight;
} ngx_http_upstream_fair_shared_t;
typedef struct ngx_http_upstream_fair_peers_s ngx_http_upstream_fair_peers_t;
typedef struct {
ngx_rbtree_node_t node;
ngx_uint_t generation;
uintptr_t peers; /* forms a unique cookie together with generation */
ngx_uint_t total_nreq;
ngx_uint_t total_requests;
ngx_atomic_t lock;
ngx_http_upstream_fair_shared_t stats[1];
} ngx_http_upstream_fair_shm_block_t;
/* ngx_spinlock is defined without a matching unlock primitive */
#define ngx_spinlock_unlock(lock) (void) ngx_atomic_cmp_set(lock, ngx_pid, 0)
typedef struct {
ngx_http_upstream_fair_shared_t *shared;
struct sockaddr *sockaddr;
socklen_t socklen;
ngx_str_t name;
ngx_uint_t weight;
ngx_uint_t max_fails;
time_t fail_timeout;
time_t accessed;
ngx_uint_t down:1;
#if (NGX_HTTP_SSL)
ngx_ssl_session_t *ssl_session; /* local to a process */
#endif
} ngx_http_upstream_fair_peer_t;
#define NGX_HTTP_UPSTREAM_FAIR_NO_RR (1<<26)
#define NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_IDLE (1<<27)
#define NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_PEAK (1<<28)
#define NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_MASK ((1<<27) | (1<<28))
enum { WM_DEFAULT = 0, WM_IDLE, WM_PEAK };
struct ngx_http_upstream_fair_peers_s {
ngx_http_upstream_fair_shm_block_t *shared;
ngx_uint_t current;
ngx_uint_t size_err:1;
ngx_uint_t no_rr:1;
ngx_uint_t weight_mode:2;
ngx_uint_t number;
ngx_str_t *name;
ngx_http_upstream_fair_peers_t *next; /* for backup peers support, not really used yet */
ngx_http_upstream_fair_peer_t peer[1];
};
#define NGX_PEER_INVALID (~0UL)
typedef struct {
ngx_http_upstream_fair_peers_t *peers;
ngx_uint_t current;
uintptr_t *tried;
uintptr_t *done;
uintptr_t data;
uintptr_t data2;
} ngx_http_upstream_fair_peer_data_t;
static ngx_int_t ngx_http_upstream_init_fair(ngx_conf_t *cf,
ngx_http_upstream_srv_conf_t *us);
static ngx_int_t ngx_http_upstream_get_fair_peer(ngx_peer_connection_t *pc,
void *data);
static void ngx_http_upstream_free_fair_peer(ngx_peer_connection_t *pc,
void *data, ngx_uint_t state);
static ngx_int_t ngx_http_upstream_init_fair_peer(ngx_http_request_t *r,
ngx_http_upstream_srv_conf_t *us);
static char *ngx_http_upstream_fair(ngx_conf_t *cf, ngx_command_t *cmd,
void *conf);
static char *ngx_http_upstream_fair_set_shm_size(ngx_conf_t *cf,
ngx_command_t *cmd, void *conf);
static ngx_int_t ngx_http_upstream_fair_init_module(ngx_cycle_t *cycle);
#if (NGX_HTTP_EXTENDED_STATUS)
static ngx_chain_t *ngx_http_upstream_fair_report_status(ngx_http_request_t *r,
ngx_int_t *length);
#endif
#if (NGX_HTTP_SSL)
static ngx_int_t ngx_http_upstream_fair_set_session(ngx_peer_connection_t *pc,
void *data);
static void ngx_http_upstream_fair_save_session(ngx_peer_connection_t *pc,
void *data);
#endif
static ngx_command_t ngx_http_upstream_fair_commands[] = {
{ ngx_string("fair"),
NGX_HTTP_UPS_CONF|NGX_CONF_ANY,
ngx_http_upstream_fair,
0,
0,
NULL },
{ ngx_string("upstream_fair_shm_size"),
NGX_HTTP_MAIN_CONF|NGX_CONF_TAKE1,
ngx_http_upstream_fair_set_shm_size,
0,
0,
NULL },
ngx_null_command
};
static ngx_http_module_t ngx_http_upstream_fair_module_ctx = {
NULL, /* preconfiguration */
NULL, /* postconfiguration */
NULL, /* create main configuration */
NULL, /* init main configuration */
NULL, /* create server configuration */
NULL, /* merge server configuration */
NULL, /* create location configuration */
NULL, /* merge location configuration */
#if (NGX_HTTP_EXTENDED_STATUS)
ngx_http_upstream_fair_report_status,
#endif
};
ngx_module_t ngx_http_upstream_fair_module = {
NGX_MODULE_V1,
&ngx_http_upstream_fair_module_ctx, /* module context */
ngx_http_upstream_fair_commands, /* module directives */
NGX_HTTP_MODULE, /* module type */
NULL, /* init master */
ngx_http_upstream_fair_init_module, /* init module */
NULL, /* init process */
NULL, /* init thread */
NULL, /* exit thread */
NULL, /* exit process */
NULL, /* exit master */
NGX_MODULE_V1_PADDING
};
static ngx_uint_t ngx_http_upstream_fair_shm_size;
static ngx_shm_zone_t * ngx_http_upstream_fair_shm_zone;
static ngx_rbtree_t * ngx_http_upstream_fair_rbtree;
static ngx_uint_t ngx_http_upstream_fair_generation;
static int
ngx_http_upstream_fair_compare_rbtree_node(const ngx_rbtree_node_t *v_left,
const ngx_rbtree_node_t *v_right)
{
ngx_http_upstream_fair_shm_block_t *left, *right;
left = (ngx_http_upstream_fair_shm_block_t *) v_left;
right = (ngx_http_upstream_fair_shm_block_t *) v_right;
if (left->generation < right->generation) {
return -1;
} else if (left->generation > right->generation) {
return 1;
} else { /* left->generation == right->generation */
if (left->peers < right->peers) {
return -1;
} else if (left->peers > right->peers) {
return 1;
} else {
return 0;
}
}
}
/*
* generic functions start here
*/
static void
ngx_rbtree_generic_insert(ngx_rbtree_node_t *temp,
ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel,
int (*compare)(const ngx_rbtree_node_t *left, const ngx_rbtree_node_t *right))
{
for ( ;; ) {
if (node->key < temp->key) {
if (temp->left == sentinel) {
temp->left = node;
break;
}
temp = temp->left;
} else if (node->key > temp->key) {
if (temp->right == sentinel) {
temp->right = node;
break;
}
temp = temp->right;
} else { /* node->key == temp->key */
if (compare(node, temp) < 0) {
if (temp->left == sentinel) {
temp->left = node;
break;
}
temp = temp->left;
} else {
if (temp->right == sentinel) {
temp->right = node;
break;
}
temp = temp->right;
}
}
}
node->parent = temp;
node->left = sentinel;
node->right = sentinel;
ngx_rbt_red(node);
}
#define NGX_BITVECTOR_ELT_SIZE (sizeof(uintptr_t) * 8)
static uintptr_t *
ngx_bitvector_alloc(ngx_pool_t *pool, ngx_uint_t size, uintptr_t *small)
{
ngx_uint_t nelts = (size + NGX_BITVECTOR_ELT_SIZE - 1) / NGX_BITVECTOR_ELT_SIZE;
if (small && nelts == 1) {
*small = 0;
return small;
}
return ngx_pcalloc(pool, nelts * NGX_BITVECTOR_ELT_SIZE);
}
static ngx_int_t
ngx_bitvector_test(uintptr_t *bv, ngx_uint_t bit)
{
ngx_uint_t n, m;
n = bit / NGX_BITVECTOR_ELT_SIZE;
m = 1 << (bit % NGX_BITVECTOR_ELT_SIZE);
return bv[n] & m;
}
static void
ngx_bitvector_set(uintptr_t *bv, ngx_uint_t bit)
{
ngx_uint_t n, m;
n = bit / NGX_BITVECTOR_ELT_SIZE;
m = 1 << (bit % NGX_BITVECTOR_ELT_SIZE);
bv[n] |= m;
}
/*
* generic functions end here
*/
static ngx_int_t
ngx_http_upstream_fair_init_module(ngx_cycle_t *cycle)
{
ngx_http_upstream_fair_generation++;
return NGX_OK;
}
static void
ngx_http_upstream_fair_rbtree_insert(ngx_rbtree_node_t *temp,
ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel) {
ngx_rbtree_generic_insert(temp, node, sentinel,
ngx_http_upstream_fair_compare_rbtree_node);
}
static ngx_int_t
ngx_http_upstream_fair_init_shm_zone(ngx_shm_zone_t *shm_zone, void *data)
{
ngx_slab_pool_t *shpool;
ngx_rbtree_t *tree;
ngx_rbtree_node_t *sentinel;
if (data) {
shm_zone->data = data;
return NGX_OK;
}
shpool = (ngx_slab_pool_t *) shm_zone->shm.addr;
tree = ngx_slab_alloc(shpool, sizeof *tree);
if (tree == NULL) {
return NGX_ERROR;
}
sentinel = ngx_slab_alloc(shpool, sizeof *sentinel);
if (sentinel == NULL) {
return NGX_ERROR;
}
ngx_rbtree_sentinel_init(sentinel);
tree->root = sentinel;
tree->sentinel = sentinel;
tree->insert = ngx_http_upstream_fair_rbtree_insert;
shm_zone->data = tree;
ngx_http_upstream_fair_rbtree = tree;
return NGX_OK;
}
static char *
ngx_http_upstream_fair_set_shm_size(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
ssize_t new_shm_size;
ngx_str_t *value;
value = cf->args->elts;
new_shm_size = ngx_parse_size(&value[1]);
if (new_shm_size == NGX_ERROR) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "Invalid memory area size `%V'", &value[1]);
return NGX_CONF_ERROR;
}
new_shm_size = ngx_align(new_shm_size, ngx_pagesize);
if (new_shm_size < 8 * (ssize_t) ngx_pagesize) {
ngx_conf_log_error(NGX_LOG_WARN, cf, 0, "The upstream_fair_shm_size value must be at least %udKiB", (8 * ngx_pagesize) >> 10);
new_shm_size = 8 * ngx_pagesize;
}
if (ngx_http_upstream_fair_shm_size &&
ngx_http_upstream_fair_shm_size != (ngx_uint_t) new_shm_size) {
ngx_conf_log_error(NGX_LOG_WARN, cf, 0, "Cannot change memory area size without restart, ignoring change");
} else {
ngx_http_upstream_fair_shm_size = new_shm_size;
}
ngx_conf_log_error(NGX_LOG_DEBUG, cf, 0, "Using %udKiB of shared memory for upstream_fair", new_shm_size >> 10);
return NGX_CONF_OK;
}
static char *
ngx_http_upstream_fair(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
ngx_http_upstream_srv_conf_t *uscf;
ngx_uint_t i;
ngx_uint_t extra_peer_flags = 0;
for (i = 1; i < cf->args->nelts; i++) {
ngx_str_t *value = cf->args->elts;
if (ngx_strcmp(value[i].data, "no_rr") == 0) {
extra_peer_flags |= NGX_HTTP_UPSTREAM_FAIR_NO_RR;
} else if (ngx_strcmp(value[i].data, "weight_mode=peak") == 0) {
if (extra_peer_flags & NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_MASK) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "weight_mode= options are mutually exclusive");
return NGX_CONF_ERROR;
}
extra_peer_flags |= NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_PEAK;
} else if (ngx_strcmp(value[i].data, "weight_mode=idle") == 0) {
if (extra_peer_flags & NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_MASK) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "weight_mode= options are mutually exclusive");
return NGX_CONF_ERROR;
}
extra_peer_flags |= NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_IDLE;
} else {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "Invalid `fair' parameter `%V'", &value[i]);
return NGX_CONF_ERROR;
}
}
uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);
uscf->peer.init_upstream = ngx_http_upstream_init_fair;
uscf->flags = NGX_HTTP_UPSTREAM_CREATE
|NGX_HTTP_UPSTREAM_WEIGHT
|NGX_HTTP_UPSTREAM_MAX_FAILS
|NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
|NGX_HTTP_UPSTREAM_DOWN
|extra_peer_flags;
return NGX_CONF_OK;
}
static ngx_int_t
ngx_http_upstream_cmp_servers(const void *one, const void *two)
{
const ngx_http_upstream_fair_peer_t *first, *second;
first = one;
second = two;
return (first->weight < second->weight);
}
/* TODO: Actually support backup servers */
static ngx_int_t
ngx_http_upstream_init_fair_rr(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
{
ngx_url_t u;
ngx_uint_t i, j, n;
ngx_http_upstream_server_t *server;
ngx_http_upstream_fair_peers_t *peers, *backup;
if (us->servers) {
server = us->servers->elts;
n = 0;
for (i = 0; i < us->servers->nelts; i++) {
if (server[i].backup) {
continue;
}
n += server[i].naddrs;
}
peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_fair_peers_t)
+ sizeof(ngx_http_upstream_fair_peer_t) * (n - 1));
if (peers == NULL) {
return NGX_ERROR;
}
peers->number = n;
peers->name = &us->host;
n = 0;
for (i = 0; i < us->servers->nelts; i++) {
for (j = 0; j < server[i].naddrs; j++) {
if (server[i].backup) {
continue;
}
peers->peer[n].sockaddr = server[i].addrs[j].sockaddr;
peers->peer[n].socklen = server[i].addrs[j].socklen;
peers->peer[n].name = server[i].addrs[j].name;
peers->peer[n].max_fails = server[i].max_fails;
peers->peer[n].fail_timeout = server[i].fail_timeout;
peers->peer[n].down = server[i].down;
peers->peer[n].weight = server[i].down ? 0 : server[i].weight;
n++;
}
}
us->peer.data = peers;
ngx_sort(&peers->peer[0], (size_t) n,
sizeof(ngx_http_upstream_fair_peer_t),
ngx_http_upstream_cmp_servers);
/* backup servers */
n = 0;
for (i = 0; i < us->servers->nelts; i++) {
if (!server[i].backup) {
continue;
}
n += server[i].naddrs;
}
if (n == 0) {
return NGX_OK;
}
backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_fair_peers_t)
+ sizeof(ngx_http_upstream_fair_peer_t) * (n - 1));
if (backup == NULL) {
return NGX_ERROR;
}
backup->number = n;
backup->name = &us->host;
n = 0;
for (i = 0; i < us->servers->nelts; i++) {
for (j = 0; j < server[i].naddrs; j++) {
if (!server[i].backup) {
continue;
}
backup->peer[n].sockaddr = server[i].addrs[j].sockaddr;
backup->peer[n].socklen = server[i].addrs[j].socklen;
backup->peer[n].name = server[i].addrs[j].name;
backup->peer[n].weight = server[i].weight;
backup->peer[n].max_fails = server[i].max_fails;
backup->peer[n].fail_timeout = server[i].fail_timeout;
backup->peer[n].down = server[i].down;
n++;
}
}
peers->next = backup;
ngx_sort(&backup->peer[0], (size_t) n,
sizeof(ngx_http_upstream_fair_peer_t),
ngx_http_upstream_cmp_servers);
return NGX_OK;
}
/* an upstream implicitly defined by proxy_pass, etc. */
if (us->port == 0 && us->default_port == 0) {
ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
"no port in upstream \"%V\" in %s:%ui",
&us->host, us->file_name, us->line);
return NGX_ERROR;
}
ngx_memzero(&u, sizeof(ngx_url_t));
u.host = us->host;
u.port = (in_port_t) (us->port ? us->port : us->default_port);
if (ngx_inet_resolve_host(cf->pool, &u) != NGX_OK) {
if (u.err) {
ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
"%s in upstream \"%V\" in %s:%ui",
u.err, &us->host, us->file_name, us->line);
}
return NGX_ERROR;
}
n = u.naddrs;
peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_fair_peers_t)
+ sizeof(ngx_http_upstream_fair_peer_t) * (n - 1));
if (peers == NULL) {
return NGX_ERROR;
}
peers->number = n;
peers->name = &us->host;
for (i = 0; i < u.naddrs; i++) {
peers->peer[i].sockaddr = u.addrs[i].sockaddr;
peers->peer[i].socklen = u.addrs[i].socklen;
peers->peer[i].name = u.addrs[i].name;
peers->peer[i].weight = 1;
peers->peer[i].max_fails = 1;
peers->peer[i].fail_timeout = 10;
}
us->peer.data = peers;
/* implicitly defined upstream has no backup servers */
return NGX_OK;
}
static ngx_int_t
ngx_http_upstream_init_fair(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
{
ngx_http_upstream_fair_peers_t *peers;
ngx_uint_t n;
ngx_str_t *shm_name;
/* do the dirty work using rr module */
if (ngx_http_upstream_init_fair_rr(cf, us) != NGX_OK) {
return NGX_ERROR;
}
/* setup our wrapper around rr */
peers = ngx_palloc(cf->pool, sizeof *peers);
if (peers == NULL) {
return NGX_ERROR;
}
peers = us->peer.data;
n = peers->number;
shm_name = ngx_palloc(cf->pool, sizeof *shm_name);
shm_name->len = sizeof("upstream_fair") - 1;
shm_name->data = (unsigned char *) "upstream_fair";
if (ngx_http_upstream_fair_shm_size == 0) {
ngx_http_upstream_fair_shm_size = 8 * ngx_pagesize;
}
ngx_http_upstream_fair_shm_zone = ngx_shared_memory_add(
cf, shm_name, ngx_http_upstream_fair_shm_size, &ngx_http_upstream_fair_module);
if (ngx_http_upstream_fair_shm_zone == NULL) {
return NGX_ERROR;
}
ngx_http_upstream_fair_shm_zone->init = ngx_http_upstream_fair_init_shm_zone;
peers->shared = NULL;
peers->current = n - 1;
if (us->flags & NGX_HTTP_UPSTREAM_FAIR_NO_RR) {
peers->no_rr = 1;
}
if (us->flags & NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_IDLE) {
peers->weight_mode = WM_IDLE;
} else if (us->flags & NGX_HTTP_UPSTREAM_FAIR_WEIGHT_MODE_PEAK) {
peers->weight_mode = WM_PEAK;
}
peers->size_err = 0;
us->peer.init = ngx_http_upstream_init_fair_peer;
return NGX_OK;
}
static void
ngx_http_upstream_fair_update_nreq(ngx_http_upstream_fair_peer_data_t *fp, int delta, ngx_log_t *log)
{
#if (NGX_DEBUG)
ngx_uint_t nreq;
ngx_uint_t total_nreq;
nreq = (fp->peers->peer[fp->current].shared->nreq += delta);
total_nreq = (fp->peers->shared->total_nreq += delta);
ngx_log_debug6(NGX_LOG_DEBUG_HTTP, log, 0,
"[upstream_fair] nreq for peer %ui @ %p/%p now %d, total %d, delta %d",
fp->current, fp->peers, fp->peers->peer[fp->current].shared, nreq,
total_nreq, delta);
#endif
}
/*
* SCHED_COUNTER_BITS is the portion of an ngx_uint_t which represents
* the req_delta part (number of requests serviced on _other_
* backends). The rest (top bits) represents the number of currently
* processed requests.
*
* The value is not too critical because overflow is handled via
* saturation. With the default value of 20, scheduling is exact for
* fewer than 4k concurrent requests per backend (on 32-bit
* architectures) and fewer than 1M concurrent requests to all backends
* together. Beyond these limits, the algorithm essentially falls back
* to pure weighted round-robin.
*
* A higher score means less suitable.
*
* The `delta' parameter is bit-negated so that high values yield low
* scores and get chosen more often.
*/
#define SCHED_COUNTER_BITS 20
#define SCHED_NREQ_MAX ((~0UL) >> SCHED_COUNTER_BITS)
#define SCHED_COUNTER_MAX ((1 << SCHED_COUNTER_BITS) - 1)
#define SCHED_SCORE(nreq,delta) (((nreq) << SCHED_COUNTER_BITS) | (~(delta) & SCHED_COUNTER_MAX))
#define ngx_upstream_fair_min(a,b) (((a) < (b)) ? (a) : (b))
static ngx_uint_t
ngx_http_upstream_fair_sched_score(ngx_peer_connection_t *pc,
ngx_http_upstream_fair_peer_data_t *fp,
ngx_uint_t n)
{
ngx_http_upstream_fair_peer_t *peer = &fp->peers->peer[n];
ngx_http_upstream_fair_shared_t *fs = peer->shared;
ngx_uint_t req_delta = fp->peers->shared->total_requests - fs->last_req_id;
/* sanity check */
if ((ngx_int_t)fs->nreq < 0) {
ngx_log_error(NGX_LOG_WARN, pc->log, 0, "[upstream_fair] upstream %ui has negative nreq (%i)", n, fs->nreq);
return SCHED_SCORE(0, req_delta);
}
ngx_log_debug3(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] peer %ui: nreq = %i, req_delta = %ui", n, fs->nreq, req_delta);
return SCHED_SCORE(
ngx_upstream_fair_min(fs->nreq, SCHED_NREQ_MAX),
ngx_upstream_fair_min(req_delta, SCHED_COUNTER_MAX));
}
/*
* the core of load balancing logic
*/
static ngx_int_t
ngx_http_upstream_fair_try_peer(ngx_peer_connection_t *pc,
ngx_http_upstream_fair_peer_data_t *fp,
ngx_uint_t peer_id)
{
ngx_http_upstream_fair_peer_t *peer;
if (ngx_bitvector_test(fp->tried, peer_id))
return NGX_BUSY;
peer = &fp->peers->peer[peer_id];
if (!peer->down) {
if (peer->max_fails == 0 || peer->shared->fails < peer->max_fails) {
return NGX_OK;
}
if (ngx_time() - peer->accessed > peer->fail_timeout) {
ngx_log_debug3(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] resetting fail count for peer %d, time delta %d > %d",
peer_id, ngx_time() - peer->accessed, peer->fail_timeout);
peer->shared->fails = 0;
return NGX_OK;
}
}
return NGX_BUSY;
}
static ngx_uint_t
ngx_http_upstream_choose_fair_peer_idle(ngx_peer_connection_t *pc,
ngx_http_upstream_fair_peer_data_t *fp)
{
ngx_uint_t i, n;
ngx_uint_t npeers = fp->peers->number;
ngx_uint_t weight_mode = fp->peers->weight_mode;
ngx_uint_t best_idx = NGX_PEER_INVALID;
ngx_uint_t best_nreq = ~0U;
for (i = 0, n = fp->current; i < npeers; i++, n = (n + 1) % npeers) {
ngx_uint_t nreq = fp->peers->peer[n].shared->nreq;
ngx_uint_t weight = fp->peers->peer[n].weight;
if (fp->peers->peer[n].shared->fails > 0)
continue;
if (nreq >= weight || (nreq > 0 && weight_mode != WM_IDLE)) {
continue;
}
if (ngx_http_upstream_fair_try_peer(pc, fp, n) != NGX_OK) {
continue;
}
/* not in WM_IDLE+no_rr mode: the first completely idle backend gets chosen */
if (weight_mode != WM_IDLE || !fp->peers->no_rr) {
best_idx = n;
break;
}
/* in WM_IDLE+no_rr mode we actually prefer slightly loaded backends
* to totally idle ones, under the assumption that they're spawned
* on demand and can handle up to 'weight' concurrent requests
*/
if (best_idx == NGX_PEER_INVALID || nreq) {
if (best_nreq <= nreq) {
continue;
}
best_idx = n;
best_nreq = nreq;
}
}
return best_idx;
}
static ngx_int_t
ngx_http_upstream_choose_fair_peer_busy(ngx_peer_connection_t *pc,
ngx_http_upstream_fair_peer_data_t *fp)
{
ngx_uint_t i, n;
ngx_uint_t npeers = fp->peers->number;
ngx_uint_t weight_mode = fp->peers->weight_mode;
ngx_uint_t best_idx = NGX_PEER_INVALID;
ngx_uint_t sched_score;
ngx_uint_t best_sched_score = ~0UL;
/*
* calculate sched scores for all the peers, choosing the lowest one
*/
for (i = 0, n = fp->current; i < npeers; i++, n = (n + 1) % npeers) {
ngx_http_upstream_fair_peer_t *peer;
ngx_uint_t nreq;
ngx_uint_t weight;
peer = &fp->peers->peer[n];
nreq = fp->peers->peer[n].shared->nreq;
if (weight_mode == WM_PEAK && nreq >= peer->weight) {
ngx_log_debug3(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] backend %d has nreq %ui >= weight %ui in WM_PEAK mode", n, nreq, peer->weight);
continue;
}
if (ngx_http_upstream_fair_try_peer(pc, fp, n) != NGX_OK) {
if (!pc->tries) {
ngx_log_debug(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] all backends exhausted");
return NGX_PEER_INVALID;
}
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] backend %d already tried", n);
continue;
}
sched_score = ngx_http_upstream_fair_sched_score(pc, fp, n);
if (weight_mode == WM_DEFAULT) {
/*
* take peer weight into account
*/
weight = peer->shared->current_weight;
if (peer->max_fails) {
ngx_uint_t mf = peer->max_fails;
weight = peer->shared->current_weight * (mf - peer->shared->fails) / mf;
}
if (weight > 0) {
sched_score /= weight;
}
ngx_log_debug8(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] bss = %ui, ss = %ui (n = %d, w = %d/%d, f = %d/%d, weight = %d)",
best_sched_score, sched_score, n, peer->shared->current_weight, peer->weight, peer->shared->fails, peer->max_fails, weight);
}
if (sched_score <= best_sched_score) {
best_idx = n;
best_sched_score = sched_score;
}
}
return best_idx;
}
static ngx_int_t
ngx_http_upstream_choose_fair_peer(ngx_peer_connection_t *pc,
ngx_http_upstream_fair_peer_data_t *fp, ngx_uint_t *peer_id)
{
ngx_uint_t npeers;
ngx_uint_t best_idx = NGX_PEER_INVALID;
ngx_uint_t weight_mode;
npeers = fp->peers->number;
weight_mode = fp->peers->weight_mode;
/* just a single backend */
if (npeers == 1) {
*peer_id = 0;
return NGX_OK;
}
/* any idle backends? */
best_idx = ngx_http_upstream_choose_fair_peer_idle(pc, fp);
if (best_idx != NGX_PEER_INVALID) {
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] peer %i is idle", best_idx);
goto chosen;
}
/* no idle backends, choose the least loaded one */
best_idx = ngx_http_upstream_choose_fair_peer_busy(pc, fp);
if (best_idx != NGX_PEER_INVALID) {
goto chosen;
}
return NGX_BUSY;
chosen:
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] chose peer %i", best_idx);
*peer_id = best_idx;
ngx_bitvector_set(fp->tried, best_idx);
if (weight_mode == WM_DEFAULT) {
ngx_http_upstream_fair_peer_t *peer = &fp->peers->peer[best_idx];
if (peer->shared->current_weight-- == 0) {
peer->shared->current_weight = peer->weight;
ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] peer %d expired weight, reset to %d", best_idx, peer->weight);
}
}
return NGX_OK;
}
ngx_int_t
ngx_http_upstream_get_fair_peer(ngx_peer_connection_t *pc, void *data)
{
ngx_int_t ret;
ngx_uint_t peer_id, i;
ngx_http_upstream_fair_peer_data_t *fp = data;
ngx_http_upstream_fair_peer_t *peer;
ngx_atomic_t *lock;
peer_id = fp->current;
fp->current = (fp->current + 1) % fp->peers->number;
lock = &fp->peers->shared->lock;
ngx_spinlock(lock, ngx_pid, 1024);
ret = ngx_http_upstream_choose_fair_peer(pc, fp, &peer_id);
ngx_log_debug3(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] fp->current = %d, peer_id = %d, ret = %d",
fp->current, peer_id, ret);
if (pc)
pc->tries--;
if (ret == NGX_BUSY) {
for (i = 0; i < fp->peers->number; i++) {
fp->peers->peer[i].shared->fails = 0;
}
pc->name = fp->peers->name;
fp->current = NGX_PEER_INVALID;
ngx_spinlock_unlock(lock);
return NGX_BUSY;
}
/* assert(ret == NGX_OK); */
peer = &fp->peers->peer[peer_id];
fp->current = peer_id;
if (!fp->peers->no_rr) {
fp->peers->current = peer_id;
}
pc->sockaddr = peer->sockaddr;
pc->socklen = peer->socklen;
pc->name = &peer->name;
peer->shared->last_req_id = fp->peers->shared->total_requests;
ngx_http_upstream_fair_update_nreq(fp, 1, pc->log);
peer->shared->total_req++;
ngx_spinlock_unlock(lock);
return ret;
}
void
ngx_http_upstream_free_fair_peer(ngx_peer_connection_t *pc, void *data,
ngx_uint_t state)
{
ngx_http_upstream_fair_peer_data_t *fp = data;
ngx_http_upstream_fair_peer_t *peer;
ngx_atomic_t *lock;
ngx_log_debug4(NGX_LOG_DEBUG_HTTP, pc->log, 0, "[upstream_fair] fp->current = %d, state = %ui, pc->tries = %d, pc->data = %p",
fp->current, state, pc->tries, pc->data);
if (fp->current == NGX_PEER_INVALID) {
return;
}
lock = &fp->peers->shared->lock;
ngx_spinlock(lock, ngx_pid, 1024);
if (!ngx_bitvector_test(fp->done, fp->current)) {
ngx_bitvector_set(fp->done, fp->current);
ngx_http_upstream_fair_update_nreq(fp, -1, pc->log);
}
if (fp->peers->number == 1) {
pc->tries = 0;
}
if (state & NGX_PEER_FAILED) {
peer = &fp->peers->peer[fp->current];
peer->shared->fails++;
peer->accessed = ngx_time();
}
ngx_spinlock_unlock(lock);
}
/*
* walk through the rbtree, removing old entries and looking for
* a matching one -- compared by (cycle, peers) pair
*
* no attempt at optimisation is made, for two reasons:
* - the tree will be quite small, anyway
* - being called once per worker startup per upstream block,
* this code isn't really the hot path
*/
static ngx_http_upstream_fair_shm_block_t *
ngx_http_upstream_fair_walk_shm(
ngx_slab_pool_t *shpool,
ngx_rbtree_node_t *node,
ngx_rbtree_node_t *sentinel,
ngx_http_upstream_fair_peers_t *peers)
{