github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/pkg/election/config.go (about)

     1  // Copyright 2022 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package election
    15  
    16  import (
    17  	"context"
    18  	"time"
    19  
    20  	"github.com/pingcap/tiflow/pkg/errors"
    21  )
    22  
    23  const (
    24  	defaultLeaseDuration  = time.Second * 10
    25  	defaultRenewInterval  = time.Second * 2
    26  	defaultRenewDeadline  = defaultLeaseDuration - defaultRenewInterval
    27  	defaultReleaseTimeout = 5 * time.Second
    28  	defaultResignTimeout  = 5 * time.Second
    29  )
    30  
    31  // Config is the configuration for the leader election.
    32  type Config struct {
    33  	// ID is id of the current member.
    34  	// It is used to distinguish different members.
    35  	// It must be unique among all members.
    36  	ID string
    37  	// Name is the human-readable name of the current member.
    38  	// It is used for logging and diagnostics.
    39  	Name string
    40  	// Address is the address of the current member.
    41  	Address string
    42  	// Storage is the storage to store the election record.
    43  	Storage Storage
    44  	// LeaderCallback is the callback function when the current member becomes leader.
    45  	// If current member loses the leadership, the ctx will be canceled. Callback should
    46  	// return as soon as possible when the ctx is canceled.
    47  	LeaderCallback func(ctx context.Context) error
    48  	// LeaseDuration is the duration that a client will wait before
    49  	// it can remove this member when the client hasn't observed any
    50  	// renewals from the member.
    51  	//
    52  	// A client will wait a full LeaseDuration without observing any
    53  	// renewals from the member before it can remove the member.
    54  	// When all clients are shutdown and a new set of clients are started
    55  	// with different id against the same storage, they must wait a full
    56  	// LeaseDuration before they can acquire a leadership. So the LeaseDuration
    57  	// should be set as short as possible to avoid the long waits in this case.
    58  	//
    59  	// It defaults to 10 seconds if not set.
    60  	LeaseDuration time.Duration
    61  	// RenewInterval is the interval that the current member tries to
    62  	// refresh the election record and renew the lease.
    63  	//
    64  	// It defaults to 2 seconds if not set.
    65  	RenewInterval time.Duration
    66  	// RenewDeadline is the duration that the current member waits before
    67  	// it gives up on the leadership when it can't renew the lease. To avoid
    68  	// two members from both acting as leader at the same time, RenewDeadline
    69  	// should be set shorter than LeaseDuration - RenewInterval.
    70  	//
    71  	// It defaults to 8 seconds if not set.
    72  	RenewDeadline time.Duration
    73  	// ExitOnRenewFail indicates whether the current member should exit when
    74  	// failing to renew the lease.
    75  	ExitOnRenewFail bool
    76  }
    77  
    78  // AdjustAndValidate adjusts the config and validates it.
    79  func (c *Config) AdjustAndValidate() error {
    80  	if c.LeaseDuration == 0 {
    81  		c.LeaseDuration = defaultLeaseDuration
    82  	}
    83  	if c.RenewInterval == 0 {
    84  		c.RenewInterval = defaultRenewInterval
    85  	}
    86  	if c.RenewDeadline == 0 {
    87  		c.RenewDeadline = defaultRenewDeadline
    88  	}
    89  	if c.ID == "" {
    90  		return errors.Errorf("id must not be empty")
    91  	}
    92  	if c.Storage == nil {
    93  		return errors.Errorf("storage must not be nil")
    94  	}
    95  	if c.LeaderCallback == nil {
    96  		return errors.Errorf("LeaderCallback must not be nil")
    97  	}
    98  	if c.RenewInterval > c.LeaseDuration {
    99  		return errors.Errorf("RenewInterval must not be greater than LeaseDuration")
   100  	}
   101  	if c.RenewDeadline > c.LeaseDuration-c.RenewInterval {
   102  		return errors.Errorf("RenewDeadline must not be greater than LeaseDuration - RenewInterval")
   103  	}
   104  	return nil
   105  }