GRPC_ARG_KEEPALIVE_TIME_MS vs GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS

[tobias....@dentsplysirona.com]

Hi,

can somebody explain the relation between these two time settings on a client perspective?

It seems to me, that GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS is the lower limit for GRPC_ARG_KEEPALIVE_TIME_MS.

But why does this GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS exists at all, when I control the rate of the ping with the KEEP_ALIVE time?

I need to detect the interruption of long living streaming channels, that might not transport any data for minutes or even hours.

Thanks

Tobias

[yas...@google.com]

Hi,

You are right. It is definitely not user friendly for someone trying to set up keepalives to also have to set GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS. I believe the reason for this is mostly to deal with the fact that pings in gRPC Core can originate via either of 3 methods -

1) Keepalive

2) BDP

3) grpc_channel_ping()

I can think of a few possible ways to improve experience here -

1) Reduce the default value of GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS

2) Use the minimum of GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS and GRPC_ARG_KEEPALIVE_TIME_MS to set the minimum ping interval without data.

3) Make GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS defunct.

[tobias....@dentsplysirona.com]

Hi,

thanks for your reply and clarifying the facts.

On Thursday, August 6, 2020 at 1:06:43 AM UTC+2, yas...@google.com wrote:

Hi,

You are right. It is definitely not user friendly for someone trying to set up keepalives to also have to set GRPC_ARG_HTTP2_MIN_SENT_PING_INTERVAL_WITHOUT_DATA_MS.

Yes. It is definitely confusing as the Keep Alive User Guide claims that 

> The above two channel arguments should be sufficient for most users, 

So you get the impression, that you need not worry about the other switches.

 

I believe the reason for this is mostly to deal with the fact that pings in gRPC Core can originate via either of 3 methods -

1) Keepalive

2) BDP

3) grpc_channel_ping()

The last one seems to be removed in the near future (https://github.com/grpc/grpc/issues/17857)

 

Thanks again.