/*
 *
 * Copyright 2017 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

// Package keepalive defines configurable parameters for point-to-point
// healthcheck.
package keepalive

import (
	"time"
)

// 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.
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.
	// If set below 10s, a minimum value of 10s will be used instead.
	//
	// Note that gRPC servers have a default EnforcementPolicy.MinTime of 5
	// minutes (which means the client shouldn't ping more frequently than every
	// 5 minutes).
	//
	// Though not ideal, it's not a strong requirement for Time to be less than
	// EnforcementPolicy.MinTime.  Time will automatically double if the server
	// disconnects due to its enforcement policy.
	//
	// For more details, see
	// https://github.com/grpc/proposal/blob/master/A8-client-side-keepalive.md
	Time time.Duration
	// 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.
	//
	// If keepalive is enabled, and this value is not explicitly set, the default
	// is 20 seconds.
	Timeout time.Duration
	// 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
}

// 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 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 time.Duration // The current default value is infinity.
	// MaxConnectionAgeGrace 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.
	// If set below 1s, a minimum value of 1s will be used instead.
	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.
	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.
type EnforcementPolicy struct {
	// 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 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.
}