Hello,
On Fri, 3 Jun 2016, Michal Kubecek wrote:
> Some users observed that "least connection" distribution algorithm doesn't
> handle well bursts of TCP connections from reconnecting clients after
> a node or network failure.
>
> This is because the algorithm counts active connection as worth 256
> inactive ones where for TCP, "active" only means TCP connections in
> ESTABLISHED state. In case of a connection burst, new connections are
> handled before previous ones have finished the three way handshaking so
> that all are still counted as "inactive", i.e. cheap ones. The become
> "active" quickly but at that time, all of them are already assigned to one
> real server (or few), resulting in highly unbalanced distribution.
>
> Address this by counting the "pre-established" states as "active".
>
> Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
Acked-by: Julian Anastasov <ja@xxxxxx>
Simon, please apply!
> ---
> net/netfilter/ipvs/ip_vs_proto_tcp.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> index d7024b2ed769..5117bcb7d2f0 100644
> --- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
> +++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> @@ -395,6 +395,20 @@ static const char *const tcp_state_name_table[IP_VS_TCP_S_LAST+1] = {
> [IP_VS_TCP_S_LAST] = "BUG!",
> };
>
> +static const bool tcp_state_active_table[IP_VS_TCP_S_LAST] = {
> + [IP_VS_TCP_S_NONE] = false,
> + [IP_VS_TCP_S_ESTABLISHED] = true,
> + [IP_VS_TCP_S_SYN_SENT] = true,
> + [IP_VS_TCP_S_SYN_RECV] = true,
> + [IP_VS_TCP_S_FIN_WAIT] = false,
> + [IP_VS_TCP_S_TIME_WAIT] = false,
> + [IP_VS_TCP_S_CLOSE] = false,
> + [IP_VS_TCP_S_CLOSE_WAIT] = false,
> + [IP_VS_TCP_S_LAST_ACK] = false,
> + [IP_VS_TCP_S_LISTEN] = false,
> + [IP_VS_TCP_S_SYNACK] = true,
> +};
> +
> #define sNO IP_VS_TCP_S_NONE
> #define sES IP_VS_TCP_S_ESTABLISHED
> #define sSS IP_VS_TCP_S_SYN_SENT
> @@ -418,6 +432,13 @@ static const char * tcp_state_name(int state)
> return tcp_state_name_table[state] ? tcp_state_name_table[state] : "?";
> }
>
> +static bool tcp_state_active(int state)
> +{
> + if (state >= IP_VS_TCP_S_LAST)
> + return false;
> + return tcp_state_active_table[state];
> +}
> +
> static struct tcp_states_t tcp_states [] = {
> /* INPUT */
> /* sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
> @@ -540,12 +561,12 @@ set_tcp_state(struct ip_vs_proto_data *pd, struct ip_vs_conn *cp,
>
> if (dest) {
> if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
> - (new_state != IP_VS_TCP_S_ESTABLISHED)) {
> + !tcp_state_active(new_state)) {
> atomic_dec(&dest->activeconns);
> atomic_inc(&dest->inactconns);
> cp->flags |= IP_VS_CONN_F_INACTIVE;
> } else if ((cp->flags & IP_VS_CONN_F_INACTIVE) &&
> - (new_state == IP_VS_TCP_S_ESTABLISHED)) {
> + tcp_state_active(new_state)) {
> atomic_inc(&dest->activeconns);
> atomic_dec(&dest->inactconns);
> cp->flags &= ~IP_VS_CONN_F_INACTIVE;
> --
> 2.8.3
Regards
--
Julian Anastasov <ja@xxxxxx>
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