On Mon, Nov 06, 2017 at 09:35:14PM +0800, 洪志道 wrote:
> Hi!
> We know that consistent hash upstream improve its selection in the latest
> version.
>
> - if (hp->tries >= points->number) {
> - pc->name = hp->rrp.peers->name;
> + if (hp->tries > 20) {
> ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
> - return NGX_BUSY;
> + return hp->get_rr_peer(pc, &hp->rrp);
>
> Does it mean that "backup" option is allowed in the module?

It just means that if, after 20 tries, we weren't able to select
a peer using the hash algorithm, then we'll continue a selection
process using the round-robin algorithm. This is also consistent
with the ip_hash module.

> |NGX_HTTP_UPSTREAM_MAX_CONNS
> |NGX_HTTP_UPSTREAM_MAX_FAILS
> |NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
> + |NGX_HTTP_UPSTREAM_BACKUP
> |NGX_HTTP_UPSTREAM_DOWN;

We do not support backup servers with ip_hash and hash balancers,
though there's currently a bypass that allows to have backup
servers in configurations with hash balancers. But these backup
servers will be used only when falling back to round-robin, which
is unlikely.

> I wonder how to archive the effect of "backup" in hash like round robin,
> even if we don't want to use error_page.

I'm not sure what did you mean here.
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