--- /dev/null
+
+/*
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+#define NGX_HTTP_UPSTREAM_LT_HEADER 0
+#define NGX_HTTP_UPSTREAM_LT_LAST_BYTE 1
+
+
+typedef struct {
+ ngx_uint_t mode;
+ ngx_uint_t use_inflight;
+ /* unsigned use_inflight:1; */
+} ngx_http_upstream_lt_conf_t;
+
+
+typedef struct {
+ /* the round robin data must be first */
+ ngx_http_upstream_rr_peer_data_t rrp;
+
+ ngx_http_upstream_lt_conf_t *conf;
+ ngx_uint_t inflight; /* unsigned inflight:1; */
+ ngx_http_upstream_t *upstream;
+} ngx_http_upstream_lt_peer_data_t;
+
+
+static ngx_int_t ngx_http_upstream_init_least_time_peer(ngx_http_request_t *r,
+ ngx_http_upstream_srv_conf_t *us);
+static ngx_int_t ngx_http_upstream_get_least_time_peer(
+ ngx_peer_connection_t *pc, void *data);
+static ngx_uint_t ngx_http_upstream_least_time_eta(
+ ngx_http_upstream_lt_peer_data_t *ltp, ngx_http_upstream_rr_peer_t *peer);
+static void ngx_http_upstream_least_time_notify(ngx_peer_connection_t *pc,
+ void *data, ngx_uint_t type);
+static void ngx_http_upstream_least_time_inflight_done(
+ ngx_http_upstream_lt_peer_data_t *ltp, ngx_http_upstream_rr_peers_t *peers,
+ ngx_http_upstream_rr_peer_t *peer, ngx_msec_t last);
+static void ngx_http_upstream_free_least_time_peer(ngx_peer_connection_t *pc,
+ void *data, ngx_uint_t state);
+
+static void *ngx_http_upstream_least_time_create_conf(ngx_conf_t *cf);
+static char *ngx_http_upstream_least_time(ngx_conf_t *cf, ngx_command_t *cmd,
+ void *conf);
+
+
+static ngx_conf_enum_t ngx_http_upstream_least_time_mode[] = {
+ { ngx_string("header"), NGX_HTTP_UPSTREAM_LT_HEADER },
+ { ngx_string("last_byte"), NGX_HTTP_UPSTREAM_LT_LAST_BYTE },
+ { ngx_null_string, 0 }
+};
+
+
+static ngx_command_t ngx_http_upstream_least_time_commands[] = {
+
+ { ngx_string("least_time"),
+ NGX_HTTP_UPS_CONF|NGX_CONF_TAKE12,
+ ngx_http_upstream_least_time,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_upstream_lt_conf_t, mode),
+ &ngx_http_upstream_least_time_mode },
+
+ ngx_null_command
+};
+
+
+static ngx_http_module_t ngx_http_upstream_least_time_module_ctx = {
+ NULL, /* preconfiguration */
+ NULL, /* postconfiguration */
+
+ NULL, /* create main configuration */
+ NULL, /* init main configuration */
+
+ ngx_http_upstream_least_time_create_conf,
+ /* create server configuration */
+ NULL, /* merge server configuration */
+
+ NULL, /* create location configuration */
+ NULL /* merge location configuration */
+};
+
+
+ngx_module_t ngx_http_upstream_least_time_module = {
+ NGX_MODULE_V1,
+ &ngx_http_upstream_least_time_module_ctx, /* module context */
+ ngx_http_upstream_least_time_commands, /* module directives */
+ NGX_HTTP_MODULE, /* module type */
+ NULL, /* init master */
+ NULL, /* init module */
+ NULL, /* init process */
+ NULL, /* init thread */
+ NULL, /* exit thread */
+ NULL, /* exit process */
+ NULL, /* exit master */
+ NGX_MODULE_V1_PADDING
+};
+
+
+static ngx_int_t
+ngx_http_upstream_init_least_time(ngx_conf_t *cf,
+ ngx_http_upstream_srv_conf_t *us)
+{
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, cf->log, 0,
+ "init least time");
+
+ if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ us->peer.init = ngx_http_upstream_init_least_time_peer;
+
+ return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_upstream_init_least_time_peer(ngx_http_request_t *r,
+ ngx_http_upstream_srv_conf_t *us)
+{
+ ngx_http_upstream_lt_conf_t *ltcf;
+ ngx_http_upstream_lt_peer_data_t *ltp;
+
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+ "init least time peer");
+
+ ltp = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_lt_peer_data_t));
+ if (ltp == NULL) {
+ return NGX_ERROR;
+ }
+
+ r->upstream->peer.data = <p->rrp;
+
+ if (ngx_http_upstream_init_round_robin_peer(r, us) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ r->upstream->peer.get = ngx_http_upstream_get_least_time_peer;
+ r->upstream->peer.free = ngx_http_upstream_free_least_time_peer;
+
+ ltp->upstream = r->upstream;
+
+ ltcf = ngx_http_conf_upstream_srv_conf(us,
+ ngx_http_upstream_least_time_module);
+
+ if (ltcf->use_inflight) {
+ r->upstream->peer.notify = ngx_http_upstream_least_time_notify;
+ }
+
+ ltp->conf = ltcf;
+
+ return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_upstream_get_least_time_peer(ngx_peer_connection_t *pc, void *data)
+{
+ ngx_http_upstream_lt_peer_data_t *ltp = data;
+
+ time_t now;
+ uintptr_t m;
+ ngx_int_t rc, total;
+ ngx_uint_t i, n, p, many, eta, best_eta;
+ ngx_msec_t ift;
+ ngx_http_upstream_rr_peer_t *peer, *best;
+ ngx_http_upstream_rr_peers_t *peers;
+ ngx_http_upstream_rr_peer_data_t *rrp;
+
+ ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+ "get least time peer, try: %ui", pc->tries);
+
+ rrp = <p->rrp;
+
+ if (rrp->peers->single) {
+ return ngx_http_upstream_get_round_robin_peer(pc, rrp);
+ }
+
+ pc->cached = 0;
+ pc->connection = NULL;
+
+ now = ngx_time();
+
+ peers = rrp->peers;
+
+ ngx_http_upstream_rr_peers_wlock(peers);
+
+#if (NGX_HTTP_UPSTREAM_ZONE)
+ if (peers->config && rrp->config != *peers->config) {
+ goto busy;
+ }
+#endif
+
+ best = NULL;
+ total = 0;
+
+#if (NGX_SUPPRESS_WARN)
+ many = 0;
+ p = 0;
+ best_eta = 0;
+#endif
+
+#if (NGX_HTTP_UPSTREAM_SID)
+ best = ngx_http_upstream_get_rr_peer_by_sid(rrp, pc->hint, &p, 0);
+
+ if (best) {
+ goto best_chosen;
+ }
+#endif
+
+ for (peer = peers->peer, i = 0;
+ peer;
+ peer = peer->next, i++)
+ {
+ n = i / (8 * sizeof(uintptr_t));
+ m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+
+ if (rrp->tried[n] & m) {
+ continue;
+ }
+
+ if (peer->down) {
+ continue;
+ }
+
+ if (peer->max_fails
+ && peer->fails >= peer->max_fails
+ && now - peer->checked <= peer->fail_timeout)
+ {
+ continue;
+ }
+
+ if (peer->max_conns && peer->conns >= peer->max_conns) {
+ continue;
+ }
+
+ if (peer->inflight_reqs > 0) {
+
+ ift = peer->inflight_last / peer->inflight_reqs
+ + (ngx_current_msec - peer->inflight_reqs_changed);
+
+ ngx_http_upstream_response_time_avg(&peer->inflight_time, ift);
+ }
+
+ /*
+ * select peer with least estimated time of processing; if there are
+ * multiple peers with the same time, select based on round-robin
+ */
+
+ eta = ngx_http_upstream_least_time_eta(ltp, peer);
+
+ if (best == NULL
+ || eta * best->weight < best_eta * peer->weight)
+ {
+ best = peer;
+ best_eta = eta;
+ many = 0;
+ p = i;
+
+ } else if (eta * best->weight == best_eta * peer->weight) {
+ many = 1;
+ }
+ }
+
+ if (best == NULL) {
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+ "get least time peer, no peer found");
+
+ goto failed;
+ }
+
+ if (many) {
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+ "get least time peer, many");
+
+ for (peer = best, i = p;
+ peer;
+ peer = peer->next, i++)
+ {
+ n = i / (8 * sizeof(uintptr_t));
+ m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+
+ if (rrp->tried[n] & m) {
+ continue;
+ }
+
+ if (peer->down) {
+ continue;
+ }
+
+ eta = ngx_http_upstream_least_time_eta(ltp, peer);
+
+ if (eta * best->weight != best_eta * peer->weight) {
+ continue;
+ }
+
+ if (peer->max_fails
+ && peer->fails >= peer->max_fails
+ && now - peer->checked <= peer->fail_timeout)
+ {
+ continue;
+ }
+
+ if (peer->max_conns && peer->conns >= peer->max_conns) {
+ continue;
+ }
+
+ peer->current_weight += peer->effective_weight;
+ total += peer->effective_weight;
+
+ if (peer->effective_weight < peer->weight) {
+ peer->effective_weight++;
+ }
+
+ if (peer->current_weight > best->current_weight) {
+ best = peer;
+ p = i;
+ }
+ }
+ }
+
+ best->current_weight -= total;
+
+#if (NGX_HTTP_UPSTREAM_SID)
+best_chosen:
+#endif
+
+ if (ltp->conf->use_inflight) {
+ if (best->inflight_reqs > 0) {
+ /* account time spent by inflight requests */
+ best->inflight_last +=
+ (ngx_current_msec - best->inflight_reqs_changed)
+ * best->inflight_reqs;
+ }
+
+ best->inflight_reqs_changed = ngx_current_msec;
+ best->inflight_reqs++;
+
+ ltp->inflight = 1;
+ }
+
+ if (now - best->checked > best->fail_timeout) {
+ best->checked = now;
+ }
+
+ pc->sockaddr = best->sockaddr;
+ pc->socklen = best->socklen;
+ pc->name = &best->name;
+
+#if (NGX_HTTP_UPSTREAM_SID)
+ pc->sid = &best->sid;
+#endif
+
+ best->conns++;
+
+ rrp->current = best;
+ ngx_http_upstream_rr_peer_ref(peers, best);
+
+ n = p / (8 * sizeof(uintptr_t));
+ m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));
+
+ rrp->tried[n] |= m;
+
+ ngx_http_upstream_rr_peers_unlock(peers);
+
+ return NGX_OK;
+
+failed:
+
+ if (peers->next) {
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+ "get least time peer, backup servers");
+
+ rrp->peers = peers->next;
+
+ n = (rrp->peers->number + (8 * sizeof(uintptr_t) - 1))
+ / (8 * sizeof(uintptr_t));
+
+ for (i = 0; i < n; i++) {
+ rrp->tried[i] = 0;
+ }
+
+ ngx_http_upstream_rr_peers_unlock(peers);
+
+ rc = ngx_http_upstream_get_least_time_peer(pc, rrp);
+
+ if (rc != NGX_BUSY) {
+ return rc;
+ }
+
+ ngx_http_upstream_rr_peers_wlock(peers);
+ }
+
+#if (NGX_HTTP_UPSTREAM_ZONE)
+busy:
+#endif
+
+ ngx_http_upstream_rr_peers_unlock(peers);
+
+ pc->name = peers->name;
+
+ return NGX_BUSY;
+}
+
+
+static ngx_uint_t
+ngx_http_upstream_least_time_eta(ngx_http_upstream_lt_peer_data_t *ltp,
+ ngx_http_upstream_rr_peer_t *peer)
+{
+ time_t now;
+ ngx_msec_t rt;
+
+ switch (ltp->conf->mode) {
+
+ case NGX_HTTP_UPSTREAM_LT_HEADER:
+ rt = peer->header_time;
+ break;
+
+ default: /* NGX_HTTP_UPSTREAM_LT_LAST_BYTE */
+ rt = peer->response_time;
+ }
+
+ now = ngx_time();
+
+ if (now - peer->checked > peer->fail_timeout) {
+ /*
+ * once in fail_timeout make response time of a peer 2 times
+ * lower to give chances to slow peers
+ */
+ rt >>= (now - peer->checked) / (peer->fail_timeout + 1);
+ }
+
+ if (peer->inflight_reqs > 0) {
+ /*
+ * average inflight time exceeding average response time indicates
+ * bad (low priority) peer
+ */
+ rt = ngx_max(rt, peer->inflight_time);
+ }
+
+ if (rt > 5000) {
+ /*
+ * consider peers with response time greater than max equally bad
+ * and thus fallback to least_conns
+ */
+ rt = 5000;
+
+ } else {
+ /*
+ * divide response times into clusters to allow round-robin for peers
+ * with close response times
+ */
+ rt += 20 - rt % 20;
+ }
+
+ /*
+ * estimated time peer has to spend to finish processing current requests
+ */
+ return rt * (1 + peer->conns);
+}
+
+
+static void
+ngx_http_upstream_least_time_notify(ngx_peer_connection_t *pc, void *data,
+ ngx_uint_t type)
+{
+ ngx_http_upstream_lt_peer_data_t *ltp = data;
+
+ ngx_msec_t last, *metric;
+ ngx_http_upstream_t *u;
+ ngx_http_upstream_rr_peer_t *peer;
+ ngx_http_upstream_rr_peers_t *peers;
+ ngx_http_upstream_rr_peer_data_t *rrp;
+
+ rrp = <p->rrp;
+
+ peers = rrp->peers;
+ peer = rrp->current;
+
+ u = ltp->upstream;
+
+ /*
+ * Only update average time here if needed for balancing.
+ * Otherwise, it will be updated in peer.free().
+ */
+
+ switch (type) {
+
+ case NGX_HTTP_UPSTREAM_NOTIFY_HEADER:
+
+ if (ltp->conf->mode != NGX_HTTP_UPSTREAM_LT_HEADER) {
+ return;
+ }
+
+ last = u->state->header_time;
+ metric = &peer->header_time;
+ break;
+
+ default:
+ return;
+ }
+
+ ngx_http_upstream_rr_peers_rlock(peers);
+ ngx_http_upstream_rr_peer_lock(peers, peer);
+
+ ngx_http_upstream_response_time_avg(metric, last);
+
+ if (ltp->inflight) {
+ ngx_http_upstream_least_time_inflight_done(ltp, peers, peer, last);
+ }
+
+ ngx_http_upstream_rr_peer_unlock(peers, peer);
+ ngx_http_upstream_rr_peers_unlock(peers);
+}
+
+
+static void
+ngx_http_upstream_least_time_inflight_done(
+ ngx_http_upstream_lt_peer_data_t *ltp, ngx_http_upstream_rr_peers_t *peers,
+ ngx_http_upstream_rr_peer_t *peer, ngx_msec_t last)
+{
+ if (peer->inflight_reqs == 1) {
+ /* no more inflight requests */
+ peer->inflight_last = 0;
+
+ } else {
+
+ /*
+ * account time spent by inflight requests and forget about
+ * request "completed" right now
+ */
+ peer->inflight_last += (ngx_current_msec - peer->inflight_reqs_changed)
+ * peer->inflight_reqs - last;
+ peer->inflight_reqs_changed = ngx_current_msec;
+ }
+
+ peer->inflight_reqs--;
+ ltp->inflight = 0;
+}
+
+
+static void
+ngx_http_upstream_free_least_time_peer(ngx_peer_connection_t *pc,
+ void *data, ngx_uint_t state)
+{
+ ngx_http_upstream_lt_peer_data_t *ltp = data;
+
+ ngx_http_upstream_t *u;
+ ngx_http_upstream_rr_peer_t *peer;
+ ngx_http_upstream_rr_peers_t *peers;
+ ngx_http_upstream_rr_peer_data_t *rrp;
+
+ ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0, "free least time peer");
+
+ rrp = <p->rrp;
+ peers = rrp->peers;
+ peer = rrp->current;
+
+ u = ltp->upstream;
+
+ ngx_http_upstream_rr_peers_rlock(peers);
+ ngx_http_upstream_rr_peer_lock(peers, peer);
+
+ if (ltp->inflight) {
+ ngx_http_upstream_least_time_inflight_done(ltp, peers, peer,
+ u->state->response_time);
+ }
+
+ /*
+ * only successful attempts are accounted to mitigate preferring
+ * of failing peers
+ */
+ if (state & (NGX_PEER_FAILED|NGX_PEER_NEXT)) {
+ goto done;
+ }
+
+ if (u->state->header_time == (ngx_msec_t) -1) {
+ goto done;
+ }
+
+ ngx_http_upstream_response_time_avg(&peer->response_time,
+ u->state->response_time);
+
+ if (ltp->conf->use_inflight
+ && ltp->conf->mode == NGX_HTTP_UPSTREAM_LT_HEADER)
+ {
+ goto done;
+ }
+
+ ngx_http_upstream_response_time_avg(&peer->header_time,
+ u->state->header_time);
+
+done:
+
+ ngx_http_upstream_free_round_robin_peer_locked(pc, rrp, state);
+}
+
+
+static void *
+ngx_http_upstream_least_time_create_conf(ngx_conf_t *cf)
+{
+ ngx_http_upstream_lt_conf_t *conf;
+
+ conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_lt_conf_t));
+ if (conf == NULL) {
+ return NULL;
+ }
+
+ /*
+ * set by ngx_pcalloc():
+ *
+ * conf->use_inflight = 0;
+ */
+
+ conf->mode = NGX_CONF_UNSET_UINT;
+
+ return conf;
+}
+
+
+static char *
+ngx_http_upstream_least_time(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+ ngx_str_t *value;
+ ngx_http_upstream_lt_conf_t *ltcf;
+ ngx_http_upstream_srv_conf_t *uscf;
+
+ uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);
+
+ if (uscf->peer.init_upstream) {
+ ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
+ "load balancing method redefined");
+ }
+
+ uscf->peer.init_upstream = ngx_http_upstream_init_least_time;
+
+ uscf->flags = NGX_HTTP_UPSTREAM_CREATE
+ |NGX_HTTP_UPSTREAM_MODIFY
+ |NGX_HTTP_UPSTREAM_WEIGHT
+ |NGX_HTTP_UPSTREAM_MAX_CONNS
+ |NGX_HTTP_UPSTREAM_MAX_FAILS
+ |NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
+ |NGX_HTTP_UPSTREAM_DOWN
+ |NGX_HTTP_UPSTREAM_BACKUP;
+
+ if (cf->args->nelts == 3) {
+ value = cf->args->elts;
+ ltcf = ngx_http_conf_upstream_srv_conf(uscf,
+ ngx_http_upstream_least_time_module);
+ if (ngx_strcmp(value[2].data, "inflight") == 0) {
+ ltcf->use_inflight = 1;
+
+ } else {
+ ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+ "invalid parameter \"%V\"", &value[2]);
+ return NGX_CONF_ERROR;
+ }
+ }
+
+ return ngx_conf_set_enum_slot(cf, cmd, conf);
+}
+
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