diff mbox

ipvs: improved SH fallback strategy

Message ID 20130926100540.GB27583@eldamar.org.uk
State Not Applicable, archived
Delegated to: David Miller
Headers show

Commit Message

Alexander Frolkin Sept. 26, 2013, 10:05 a.m. UTC 
Improve the SH fallback realserver selection strategy.

With sh and sh-fallback, if a realserver is down, this attempts to
distribute the traffic that would have gone to that server evenly
among the remaining servers.

Signed-off-by: Alexander Frolkin <avf@eldamar.org.uk>

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Comments

Julian Anastasov Sept. 26, 2013, 8:05 p.m. UTC | #1 
Hello,

On Thu, 26 Sep 2013, Alexander Frolkin wrote:

> Improve the SH fallback realserver selection strategy.
> 
> With sh and sh-fallback, if a realserver is down, this attempts to
> distribute the traffic that would have gone to that server evenly
> among the remaining servers.
> 
> Signed-off-by: Alexander Frolkin <avf@eldamar.org.uk>

	Looks correct to me, just fix the below indentations.
Also, please use version number for your patches, eg.
[PATCHv2] ipvs: ...

> diff --git a/net/netfilter/ipvs/ip_vs_sh.c b/net/netfilter/ipvs/ip_vs_sh.c
> index 3588fae..533ea53 100644
> --- a/net/netfilter/ipvs/ip_vs_sh.c
> +++ b/net/netfilter/ipvs/ip_vs_sh.c

> +	IP_VS_DBG_BUF(6, "SH: selected unavailable server "
> +		"%s:%d, reselecting",
> +		IP_VS_DBG_ADDR(svc->af, &dest->addr),
> +		ntohs(dest->port));

	Indentation:

	IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
		      IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port));


> +		IP_VS_DBG_BUF(6, "SH: selected unavailable "
> +			"server %s:%d (offset %d), reselecting",
> +			IP_VS_DBG_ADDR(svc->af, &dest->addr),
> +			ntohs(dest->port),
> +			roffset);

	Indentation:

		IP_VS_DBG_BUF(6, "SH: selected unavailable "
			      "server %s:%d (offset %d), reselecting",
			      IP_VS_DBG_ADDR(svc->af, &dest->addr),
			      ntohs(dest->port), roffset);

Regards

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Julian Anastasov <ja@ssi.bg>
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diff mbox

Patch

diff --git a/net/netfilter/ipvs/ip_vs_sh.c b/net/netfilter/ipvs/ip_vs_sh.c
index 3588fae..533ea53 100644
--- a/net/netfilter/ipvs/ip_vs_sh.c
+++ b/net/netfilter/ipvs/ip_vs_sh.c
@@ -115,27 +115,49 @@  ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
 }
 
 
-/* As ip_vs_sh_get, but with fallback if selected server is unavailable */
+/* As ip_vs_sh_get, but with fallback if selected server is unavailable
+ *
+ * The fallback strategy loops around the table starting from a "random"
+ * point (in fact, it is chosen to be the original hash value to make the
+ * algorithm deterministic) to find a new server.
+ */
 static inline struct ip_vs_dest *
 ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
 		      const union nf_inet_addr *addr, __be16 port)
 {
-	unsigned int offset;
-	unsigned int hash;
+	unsigned int offset, roffset;
+	unsigned int hash, ihash;
 	struct ip_vs_dest *dest;
 
+	/* first try the dest it's supposed to go to */
+	ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
+	dest = rcu_dereference(s->buckets[ihash].dest);
+	if (!dest)
+		return NULL;
+	if (!is_unavailable(dest))
+		return dest;
+
+	IP_VS_DBG_BUF(6, "SH: selected unavailable server "
+		"%s:%d, reselecting",
+		IP_VS_DBG_ADDR(svc->af, &dest->addr),
+		ntohs(dest->port));
+
+	/* if the original dest is unavailable, loop around the table
+	 * starting from ihash to find a new dest
+	 */
 	for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
-		hash = ip_vs_sh_hashkey(svc->af, addr, port, offset);
+		roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
+		hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset);
 		dest = rcu_dereference(s->buckets[hash].dest);
 		if (!dest)
 			break;
-		if (is_unavailable(dest))
-			IP_VS_DBG_BUF(6, "SH: selected unavailable server "
-				      "%s:%d (offset %d)",
-				      IP_VS_DBG_ADDR(svc->af, &dest->addr),
-				      ntohs(dest->port), offset);
-		else
+		if (!is_unavailable(dest))
 			return dest;
+		IP_VS_DBG_BUF(6, "SH: selected unavailable "
+			"server %s:%d (offset %d), reselecting",
+			IP_VS_DBG_ADDR(svc->af, &dest->addr),
+			ntohs(dest->port),
+			roffset);
 	}
 
 	return NULL;