tidb placement 源码

tidb placement 代码

文件路径：/store/pdtypes/placement.go

// Copyright 2022 PingCAP, Inc.
//
// 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 pdtypes

// Rule is the placement rule that can be checked against a region. When
// applying rules (apply means schedule regions to match selected rules), the
// apply order is defined by the tuple [GroupIndex, GroupID, Index, ID].
type Rule struct {
	GroupID          string            `json:"group_id"`                    // mark the source that add the rule
	ID               string            `json:"id"`                          // unique ID within a group
	Index            int               `json:"index,omitempty"`             // rule apply order in a group, rule with less ID is applied first when indexes are equal
	Override         bool              `json:"override,omitempty"`          // when it is true, all rules with less indexes are disabled
	StartKey         []byte            `json:"-"`                           // range start key
	StartKeyHex      string            `json:"start_key"`                   // hex format start key, for marshal/unmarshal
	EndKey           []byte            `json:"-"`                           // range end key
	EndKeyHex        string            `json:"end_key"`                     // hex format end key, for marshal/unmarshal
	Role             PeerRoleType      `json:"role"`                        // expected role of the peers
	Count            int               `json:"count"`                       // expected count of the peers
	LabelConstraints []LabelConstraint `json:"label_constraints,omitempty"` // used to select stores to place peers
	LocationLabels   []string          `json:"location_labels,omitempty"`   // used to make peers isolated physically
	IsolationLevel   string            `json:"isolation_level,omitempty"`   // used to isolate replicas explicitly and forcibly
	Version          uint64            `json:"version,omitempty"`           // only set at runtime, add 1 each time rules updated, begin from 0.
	CreateTimestamp  uint64            `json:"create_timestamp,omitempty"`  // only set at runtime, recorded rule create timestamp
}

// PeerRoleType is the expected peer type of the placement rule.
type PeerRoleType string

const (
	// Voter can either match a leader peer or follower peer
	Voter PeerRoleType = "voter"
	// Leader matches a leader.
	Leader PeerRoleType = "leader"
	// Follower matches a follower.
	Follower PeerRoleType = "follower"
	// Learner matches a learner.
	Learner PeerRoleType = "learner"
)

// LabelConstraint is used to filter store when trying to place peer of a region.
type LabelConstraint struct {
	Key    string            `json:"key,omitempty"`
	Op     LabelConstraintOp `json:"op,omitempty"`
	Values []string          `json:"values,omitempty"`
}

// RuleGroup defines properties of a rule group.
type RuleGroup struct {
	ID       string `json:"id,omitempty"`
	Index    int    `json:"index,omitempty"`
	Override bool   `json:"override,omitempty"`
}

// LabelConstraintOp defines how a LabelConstraint matches a store. It can be one of
// 'in', 'notIn', 'exists', or 'notExists'.
type LabelConstraintOp string

const (
	// In restricts the store label value should in the value list.
	// If label does not exist, `in` is always false.
	In LabelConstraintOp = "in"
	// NotIn restricts the store label value should not in the value list.
	// If label does not exist, `notIn` is always true.
	NotIn LabelConstraintOp = "notIn"
	// Exists restricts the store should have the label.
	Exists LabelConstraintOp = "exists"
	// NotExists restricts the store should not have the label.
	NotExists LabelConstraintOp = "notExists"
)

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