Multiple active gateways

[cangyin]

What would you like to be added:

Multiple active gateways for higher inter-cluster data transfer performance.

Why is this needed:

Currently there is only one gateway per cluster. As per the benchmark result in #2890, there is significant performance drop (about 56%) for PODs running on non-gateway nodes. Suppose the gateway node has a 10Gbit/s NIC. For DBMS servers running on non-gateway nodes, they only share 560 MByte/s. This means the whole cluster is only able to transfer 46TB of data per day at maximum, theoretically, which is unacceptable for productional clusters (JFYI, a small to median sized productional ClickHouse cluster can receive more than 40TB of data per day).

[skitt]

With the default IPsec tunnels, this happens because the IPsec protocol doesn’t support splitting tunnels, and the encryption and packet ordering must happen on a single core.

We have considered in the past enabling multiple parallel tunnels, on one gateway or across multiple gateways (in the latter case, with added HA benefits); but that requires deciding how to split traffic across the available tunnels.

In parallel, protocol extensions are being discussed to allow IPsec tunnels to be split to avoid these bottlenecks; see the current draft for details. It seems preferable for Submariner to support that, once it becomes available, instead of coming up with its own solution.

For performance-critical scenarios, especially in cases where a dedicated (private) network is available between gateways, Submariner supports VXLAN tunnels instead of IPsec.

[cangyin]

For performance-critical scenarios, especially in cases where a dedicated (private) network is available between gateways, Submariner supports VXLAN tunnels instead of IPsec.

The 56% performance drop in question is exactly that of inter-cluster VXLAN tunnel (vxlan-tunnel VTEP). Which gives 44% of underlying network capability of only one NIC, while the IPsec tunnel gives 26%.

It seems multiple active VXLAN gateways is easier to implement, intuitively.

[dfarrell07]

protocol extensions are being discussed to allow IPsec tunnels to be split to avoid these bottlenecks

If we go this path, we should likely raise a more specific issue.

[maayanf24]

Need more investigation before prioritizing.
First we want to implement load-balancer mode.

[maayanf24]

Decided to push to following releases