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keepalive: godoc improvement and behavior explanation (#2342)

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Menghan Li 2018-10-02 13:03:51 -07:00 committed by GitHub
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Documentation/keepalive.md Normal file
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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#ServerParameters) 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

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keepalive/keepalive.go
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*
*/
// Package keepalive defines configurable parameters for point-to-point healthcheck.
// Package keepalive defines configurable parameters for point-to-point
// healthcheck.
package keepalive
import (
@ -24,42 +25,59 @@ import (
)
// ClientParameters is used to set keepalive parameters on the client-side.
// These configure how the client will actively probe to notice when a connection is broken
// and send pings so intermediaries will be aware of the liveness of the connection.
// Make sure these parameters are set in coordination with the keepalive policy on the server,
// as incompatible settings can result in closing of connection.
// These configure how the client will actively probe to notice when a
// connection is broken and send pings so intermediaries will be aware of the
// liveness of the connection. Make sure these parameters are set in
// coordination with the keepalive policy on the server, as incompatible
// settings can result in closing of connection.
type ClientParameters struct {
// After a duration of this time if the client doesn't see any activity it pings the server to see if the transport is still alive.
// After a duration of this time if the client doesn't see any activity it
// pings the server to see if the transport is still alive.
Time time.Duration // The current default value is infinity.
// After having pinged for keepalive check, the client waits for a duration of Timeout and if no activity is seen even after that
// the connection is closed.
// After having pinged for keepalive check, the client waits for a duration
// of Timeout and if no activity is seen even after that the connection is
// closed.
Timeout time.Duration // The current default value is 20 seconds.
// If true, client runs keepalive checks even with no active RPCs.
// If true, client sends keepalive pings even with no active RPCs. If false,
// when there are no active RPCs, Time and Timeout will be ignored and no
// keepalive pings will be sent.
PermitWithoutStream bool // false by default.
}
// ServerParameters is used to set keepalive and max-age parameters on the server-side.
// ServerParameters is used to set keepalive and max-age parameters on the
// server-side.
type ServerParameters struct {
// MaxConnectionIdle is a duration for the amount of time after which an idle connection would be closed by sending a GoAway.
// Idleness duration is defined since the most recent time the number of outstanding RPCs became zero or the connection establishment.
// MaxConnectionIdle is a duration for the amount of time after which an
// idle connection would be closed by sending a GoAway. Idleness duration is
// defined since the most recent time the number of outstanding RPCs became
// zero or the connection establishment.
MaxConnectionIdle time.Duration // The current default value is infinity.
// MaxConnectionAge is a duration for the maximum amount of time a connection may exist before it will be closed by sending a GoAway.
// A random jitter of +/-10% will be added to MaxConnectionAge to spread out connection storms.
// MaxConnectionAge is a duration for the maximum amount of time a
// connection may exist before it will be closed by sending a GoAway. A
// random jitter of +/-10% will be added to MaxConnectionAge to spread out
// connection storms.
MaxConnectionAge time.Duration // The current default value is infinity.
// MaxConnectinoAgeGrace is an additive period after MaxConnectionAge after which the connection will be forcibly closed.
// MaxConnectinoAgeGrace is an additive period after MaxConnectionAge after
// which the connection will be forcibly closed.
MaxConnectionAgeGrace time.Duration // The current default value is infinity.
// After a duration of this time if the server doesn't see any activity it pings the client to see if the transport is still alive.
// After a duration of this time if the server doesn't see any activity it
// pings the client to see if the transport is still alive.
Time time.Duration // The current default value is 2 hours.
// After having pinged for keepalive check, the server waits for a duration of Timeout and if no activity is seen even after that
// the connection is closed.
// After having pinged for keepalive check, the server waits for a duration
// of Timeout and if no activity is seen even after that the connection is
// closed.
Timeout time.Duration // The current default value is 20 seconds.
}
// EnforcementPolicy is used to set keepalive enforcement policy on the server-side.
// Server will close connection with a client that violates this policy.
// EnforcementPolicy is used to set keepalive enforcement policy on the
// server-side. Server will close connection with a client that violates this
// policy.
type EnforcementPolicy struct {
// MinTime is the minimum amount of time a client should wait before sending a keepalive ping.
// MinTime is the minimum amount of time a client should wait before sending
// a keepalive ping.
MinTime time.Duration // The current default value is 5 minutes.
// If true, server expects keepalive pings even when there are no active streams(RPCs).
// If true, server allows keepalive pings even when there are no active
// streams(RPCs). If false, and client sends ping when there are no active
// streams, server will send GOAWAY and close the connection.
PermitWithoutStream bool // false by default.
}