Allow setting grpc send and recv message sizes independently

[henryr]

We would like to set the send and recv max message sizes independently on vtgates. This allows us to keep a small limit on the size of the messages received from tablets, while allowing vtgates to send a large aggregated response to clients.

Two new flags are added: grpc_max_message_send_size and grpc_max_message_recv_size. These are 0 by default, in which case the existing grpc_max_message_size flag is used with no change from the existing behaviour. If set to non-0, they override the setting for grpc_max_message_size.

[rjlaine]

LGTM

[pbibra]

this lgtm! I think we'll want to update all the txt help files with the two new flags to get some of the unit tests passing. Since they all use these grpc common options

topo2topo.txt
vtbackup.txt
vtbench.txt
vtclient.txt
vtcombo.txt
vtctlclient.txt
vtctld.txt
vtctldclient.txt
vtgate.txt
vtgateclienttest.txt
vtorc.txt
vttablet.txt
vttestserver.txt

[henryr]

@pbibra where are those files? I don't see them in my slack-15 checkout (alternatively, which tests should I run locally to trigger those failures?)

[henryr]

@pbibra I found some of them, let me know if others (like topo2topo.txt) still need updating.

[pbibra]

@pbibra I found some of them, let me know if others (like topo2topo.txt) still need updating.

No sorry! That list was from the v19 branch - you got all of them here! The tests are in flags_test.go and can be run locally after running make build.

/usr/bin/go test -timeout 30s -run ^TestHelpOutput$ vitess.io/vitess/go/flags/endtoend