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nginx-sso/vendor/google.golang.org/grpc/Documentation/keepalive.md

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# Keepalive
gRPC sends http2 pings on the transport to detect if the connection is down. If
the ping is not acknowledged by the other side within a certain period, the
connection will be close. Note that pings are only necessary when there's no
activity on the connection.
For how to configure keepalive, see
https://godoc.org/google.golang.org/grpc/keepalive for the options.
## What should I set?
It should be sufficient for most users to set [client
parameters](https://godoc.org/google.golang.org/grpc/keepalive) as a [dial
option](https://godoc.org/google.golang.org/grpc#WithKeepaliveParams).
## What will happen?
(The behavior described here is specific for gRPC-go, it might be slightly
different in other languages.)
When there's no activity on a connection (note that an ongoing stream results in
__no activity__ when there's no message being sent), after `Time`, a ping will
be sent by the client and the server will send a ping ack when it gets the ping.
Client will wait for `Timeout`, and check if there's any activity on the
connection during this period (a ping ack is an activity).
## What about server side?
Server has similar `Time` and `Timeout` settings as client. Server can also
configure connection max-age. See [server
parameters](https://godoc.org/google.golang.org/grpc/keepalive#ServerParameters)
for details.
### Enforcement policy
[Enforcement
policy](https://godoc.org/google.golang.org/grpc/keepalive#EnforcementPolicy) is
a special setting on server side to protect server from malicious or misbehaving
clients.
Server sends GOAWAY with ENHANCE_YOUR_CALM and close the connection when bad
behaviors are detected:
- Client sends too frequent pings
- Client sends pings when there's no stream and this is disallowed by server
config