[PATCH 1 of 9] Upstream: re-resolvable servers

[Mathew Heard]

Do you happen to know if there remains any gap in obvious capability
provided by a module like jdomain compared to this?

Perhaps it would be worth checking to ensure nothing obvious is not
implemented?

The one that I see is the ability to control if a resolution is IPv4, IPv6
or mixed. Is this something that would be useful for this feature?

On Fri, 12 Jul 2024 at 02:40, Aleksei Bavshin <a.bavshin at nginx.com> wrote:

> On 7/9/2024 9:22 AM, Roman Arutyunyan wrote:
> > Hi,
> >
> > On Mon, Jul 08, 2024 at 06:20:58PM +0400, Roman Arutyunyan wrote:
> >> Hi,
> >>
> >> On Thu, Jun 13, 2024 at 03:28:56PM -0700, Aleksei Bavshin wrote:
> >>> # HG changeset patch
> >>> # User Ruslan Ermilov <ru at nginx.com>
> >>> # Date 1392462754 -14400
> >>> #      Sat Feb 15 15:12:34 2014 +0400
> >>> # Node ID 56aeae9355df8a2ee07e21b65b6869747dd9ee45
> >>> # Parent  02e9411009b987f408214ab4a8b6b6093f843bcd
> >>> Upstream: re-resolvable servers.
> >>>
> >>> Specifying the upstream server by a hostname together with the
> >>> "resolve" parameter will make the hostname to be periodically
> >>> resolved, and upstream servers added/removed as necessary.
> >>>
> >>> This requires a "resolver" at the "http" configuration block.
> >>>
> >>> The "resolver_timeout" parameter also affects when the failed
> >>> DNS requests will be attempted again.  Responses with NXDOMAIN
> >>> will be attempted again in 10 seconds.
> >>>
> >>> Upstream has a configuration generation number that is incremented each
> >>> time servers are added/removed to the primary/backup list.  This number
> >>> is remembered by the peer.init method, and if peer.get detects a change
> >>> in configuration, it returns NGX_BUSY.
> >>>
> >>> Each server has a reference counter.  It is incremented by peer.get and
> >>> decremented by peer.free.  When a server is removed, it is removed from
> >>> the list of servers and is marked as "zombie".  The memory allocated by
> >>> a zombie peer is freed only when its reference count becomes zero.
> >>>
> >>> Re-resolvable servers utilize timers that also hold a reference.  A
> >>> reference is also held while upstream keepalive caches an idle
> >>> connection.
> >>>
> >>> Co-authored-by: Roman Arutyunyan <arut at nginx.com>
> >>> Co-authored-by: Sergey Kandaurov <pluknet at nginx.com>
> >>> Co-authored-by: Vladimir Homutov <vl at nginx.com>
> >
> > [..]
> >
> >>> diff --git a/src/http/ngx_http_upstream_round_robin.h
> b/src/http/ngx_http_upstream_round_robin.h
> >>> --- a/src/http/ngx_http_upstream_round_robin.h
> >>> +++ b/src/http/ngx_http_upstream_round_robin.h
> >>> @@ -14,8 +14,23 @@
> >>>   #include <ngx_http.h>
> >>>
> >>>
> >>> +typedef struct ngx_http_upstream_rr_peers_s
> ngx_http_upstream_rr_peers_t;
> >>>   typedef struct ngx_http_upstream_rr_peer_s
>  ngx_http_upstream_rr_peer_t;
> >>>
> >>> +
> >>> +#if (NGX_HTTP_UPSTREAM_ZONE)
> >>> +
> >>> +typedef struct {
> >>> +    ngx_event_t                     event;         /* must be first */
> >>> +    ngx_uint_t                      worker;
> >
> > Missed this last time.  This field should be removed since all resolving
> is in
> > worker #0.
>
> Unfortunately, that would break the ABI compatibility between OSS and
> Plus. Replacing the field with yet another NGX_COMPAT_BEGIN isn't any
> better than leaving it in the opensource code.
>
> >
> >>> +    ngx_str_t                       name;
> >>> +    ngx_http_upstream_rr_peers_t   *peers;
> >>> +    ngx_http_upstream_rr_peer_t    *peer;
> >>> +} ngx_http_upstream_host_t;
> >>> +
> >>> +#endif
> >>> +
> >>> +
> >>>   struct ngx_http_upstream_rr_peer_s {
> >>>       struct sockaddr                *sockaddr;
> >>>       socklen_t                       socklen;
> >>> @@ -46,7 +61,12 @@ struct ngx_http_upstream_rr_peer_s {
> >>>   #endif
> >>>
> >>>   #if (NGX_HTTP_UPSTREAM_ZONE)
> >>> +    unsigned                        zombie:1;
> >>
> >> I suggest declaring this as in other similar places:
> >>
> >>         ngx_uint_t                      zombie; /* unsigned  zombie:1;
> */
> >>
> >>> +
> >>>       ngx_atomic_t                    lock;
> >>> +    ngx_uint_t                      id;
> >>
> >> This field is not used in open source nginx and should not be added or
> assigned.
> >>
> >>> +    ngx_uint_t                      refs;
> >>> +    ngx_http_upstream_host_t       *host;
> >>>   #endif
> >>>
> >>>       ngx_http_upstream_rr_peer_t    *next;
> >
> > [..]
> >
> > --
> > Roman Arutyunyan
> > _______________________________________________
> > nginx-devel mailing list
> > nginx-devel at nginx.org
> > https://mailman.nginx.org/mailman/listinfo/nginx-devel
> _______________________________________________
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>
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