diff options
author | Roman Arutyunyan <arut@nginx.com> | 2016-01-28 15:28:20 +0300 |
---|---|---|
committer | Roman Arutyunyan <arut@nginx.com> | 2016-01-28 15:28:20 +0300 |
commit | c8c44f74783d699474b32a59f525a3ef4dfbecf5 (patch) | |
tree | 865930ecccbf3fdd22f9d698fbf579ea37096dbb /src/core/ngx_resolver.c | |
parent | 1945fff7bfee1eef23933faa0ccfbe05445dcfe1 (diff) |
Resolver: per-request DNS server balancer.
Previously, a global server balancer was used to assign the next DNS server to
send a query to. That could lead to a non-uniform distribution of servers per
request. A request could be assigned to the same dead server several times in a
row and wait longer for a valid server or even time out without being processed.
Now each query is sent to all servers sequentially in a circle until a
response is received or timeout expires. Initial server for each request is
still globally balanced.
Diffstat (limited to 'src/core/ngx_resolver.c')
-rw-r--r-- | src/core/ngx_resolver.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c index a9185529e..ac0d54dcd 100644 --- a/src/core/ngx_resolver.c +++ b/src/core/ngx_resolver.c @@ -685,6 +685,11 @@ ngx_resolve_name_locked(ngx_resolver_t *r, ngx_resolver_ctx_t *ctx, return NGX_OK; } + rn->last_connection = r->last_connection++; + if (r->last_connection == r->connections.nelts) { + r->last_connection = 0; + } + rn->naddrs = (u_short) -1; #if (NGX_HAVE_INET6) rn->naddrs6 = r->ipv6 ? (u_short) -1 : 0; @@ -897,6 +902,11 @@ ngx_resolve_addr(ngx_resolver_ctx_t *ctx) goto failed; } + rn->last_connection = r->last_connection++; + if (r->last_connection == r->connections.nelts) { + r->last_connection = 0; + } + rn->naddrs = (u_short) -1; #if (NGX_HAVE_INET6) rn->naddrs6 = (u_short) -1; @@ -1098,11 +1108,7 @@ ngx_resolver_send_query(ngx_resolver_t *r, ngx_resolver_node_t *rn) ngx_resolver_connection_t *rec; rec = r->connections.elts; - - rec = &rec[r->last_connection++]; - if (r->last_connection == r->connections.nelts) { - r->last_connection = 0; - } + rec = &rec[rn->last_connection]; if (rec->udp == NULL) { @@ -1244,6 +1250,10 @@ ngx_resolver_resend(ngx_resolver_t *r, ngx_rbtree_t *tree, ngx_queue_t *queue) if (rn->waiting) { + if (++rn->last_connection == r->connections.nelts) { + rn->last_connection = 0; + } + (void) ngx_resolver_send_query(r, rn); rn->expire = now + r->resend_timeout; |