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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 closed. Note that pings are only necessary when there is no activity on the connection.

What should I set?

It should be sufficient for most users to only change interval and timeout properties, but the following properties can also be useful in certain use cases.

Property Client Server Description
interval Int64.max (disabled) .hours(2) The amount of time to wait before sending a keepalive ping.
timeout .seconds(20) .seconds(20) The amount of time to wait for an acknowledgment. This value must be less than interval.
permitWithoutCalls false false Send keepalive pings even if there are no calls in flight.
maximumPingsWithoutData 2 2 Maximum number of pings that can be sent when there is no data/header frame to be sent/
minimumSentPingIntervalWithoutData .minutes(5) .minutes(5) If there are no data/header frames being received: the minimum amount of time to wait between successive pings.
minimumReceivedPingIntervalWithoutData N/A .minutes(5) If there are no data/header frames being sent: the minimum amount of time expected between receiving successive pings. If the time between successive pings is less than this value, then the ping will be considered a bad ping from the peer. Such a ping counts as a "ping strike".
maximumPingStrikes N/A 2 Maximum number of bad pings that the server will tolerate before sending an HTTP2 GOAWAY frame and closing the connection. Setting it to 0 allows the server to accept any number of bad pings.

Client

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)

let keepalive = ClientConnectionKeepalive(
  interval: .seconds(15),
  timeout: .seconds(10)
)

let channel = try GRPCChannelPool.with(
  target: .host("localhost"),
  transportSecurity: .tls(...),
  eventLoopGroup: group
) {
  // Configure keepalive.
  $0.keepalive = keepalive
}

Server

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)

let keepalive = ServerConnectionKeepalive(
  interval: .seconds(15),
  timeout: .seconds(10)
)

let configuration = Server.Configuration(
  target: .hostAndPort("localhost", 443),
  eventLoopGroup: group,
  connectionKeepalive: keepalive,
  serviceProviders: [YourCallHandlerProvider()]
)

let server = Server.makeBootstrap(configuration: configuration)

Fore more information, please visit the gRPC Core documentation for keepalive