InfluxDB meta文件解析_ZenDei技術網路在線

操作系統： CentOS7.3.1611_x64 go語言版本：1.8.3 linux/amd64 InfluxDB版本：1.1.0 influxdb預設配置： meta預設配置： dir meta數據存放目錄，預設值：/var/lib/influxdb/meta meta數據文件預設路徑：/va ...

操作系統： CentOS7.3.1611_x64

go語言版本：1.8.3 linux/amd64

InfluxDB版本：1.1.0

influxdb預設配置：

/etc/influxdb/influxdb.conf

meta預設配置：

[meta]
  dir = "/var/lib/influxdb/meta"
  retention-autocreate = true
  logging-enabled = true

meta數據存放目錄，預設值：/var/lib/influxdb/meta

meta數據文件預設路徑：/var/lib/influxdb/meta/meta.db

retention-autocreate

用於控制預設存儲策略，資料庫創建時，會自動生成autogen的存儲策略，預設值：true

logging-enabled

是否開啟meta日誌，預設值：true

meta文件的dump和load

源碼路徑： github.com/influxdata/influxdb/services/meta/client.go

meta文件dump

// snapshot will save the current meta data to disk
func snapshot(path string, data *Data) error {
    file := filepath.Join(path, metaFile)
    tmpFile := file + "tmp"

    f, err := os.Create(tmpFile)
    if err != nil {
        return err
    }
    defer f.Close()

    var d []byte
    if b, err := data.MarshalBinary(); err != nil {
        return err
    } else {
        d = b
    }

    if _, err := f.Write(d); err != nil {
        return err
    }

    if err = f.Sync(); err != nil {
        return err
    }

    //close file handle before renaming to support Windows
    if err = f.Close(); err != nil {
        return err
    }

    return renameFile(tmpFile, file)
}

snapshot可以通過以下兩種方式觸發：

1、當執行 Client.Open 函數時會進行snapshot操作；

2、執行meta文件更新時通過commit函數進行snapshot操作；

在InfluxDB中程式中，通過 NewServer 函數創建MetaClient變數（meta.NewClient），然後執行MetaClient.Open()進行初始化；

後續會通過Server.Open函數（run/server.go）啟動各項服務，如果有meta文件的更新操作，通過commit函數進行snapshot操作；

meta文件load

// Load will save the current meta data from disk
func (c *Client) Load() error {
    file := filepath.Join(c.path, metaFile)

    f, err := os.Open(file)
    if err != nil {
        if os.IsNotExist(err) {
            return nil
        }
        return err
    }
    defer f.Close()

    data, err := ioutil.ReadAll(f)
    if err != nil {
        return err
    }

    if err := c.cacheData.UnmarshalBinary(data); err != nil {
        return err
    }
    return nil
}

Client.Open()中會執行Load操作，NewServer時會自動載入。

meta文件內容編解碼

源碼路徑： github.com/influxdata/influxdb/services/meta/data.go

meta數據encode：

// MarshalBinary encodes the metadata to a binary format.
func (data *Data) MarshalBinary() ([]byte, error) {
    return proto.Marshal(data.marshal())
}

meta數據decode：

// UnmarshalBinary decodes the object from a binary format.
func (data *Data) UnmarshalBinary(buf []byte) error {
    var pb internal.Data
    if err := proto.Unmarshal(buf, &pb); err != nil {
        return err
    }
    data.unmarshal(&pb)
    return nil
}

proto路徑：github.com/gogo/protobuf/proto

meta文件結構定義

源碼路徑： github.com/influxdata/influxdb/services/meta/data.go

meta文件存儲的就是 meta.Data 的數據，結構定義如下：

// Data represents the top level collection of all metadata.
type Data struct {
    Term      uint64 // associated raft term
    Index     uint64 // associated raft index
    ClusterID uint64
    Databases []DatabaseInfo
    Users     []UserInfo

    MaxShardGroupID uint64
    MaxShardID      uint64
}

Term ：暫時不知道乾什麼用的。

Index ：從源碼看這個應該是類似版本號的東西，初始化為1，執行commit操作是會增加。如果為1，會立即執行持久化操作（在Open函數中操作）。

ClusterID ：是InfluxDB集群相關內容；

Databases ：用於存儲資料庫信息；

Users ：用於存儲資料庫用戶信息；

DatabaseInfo 定義：

// DatabaseInfo represents information about a database in the system.
type DatabaseInfo struct {
    Name                   string
    DefaultRetentionPolicy string
    RetentionPolicies      []RetentionPolicyInfo
    ContinuousQueries      []ContinuousQueryInfo
}

RetentionPolicyInfo 定義：

// RetentionPolicyInfo represents metadata about a retention policy.
type RetentionPolicyInfo struct {
    Name               string
    ReplicaN           int
    Duration           time.Duration
    ShardGroupDuration time.Duration
    ShardGroups        []ShardGroupInfo
    Subscriptions      []SubscriptionInfo
}

ShardGroupInfo 定義：

// ShardGroupInfo represents metadata about a shard group. The DeletedAt field is important
// because it makes it clear that a ShardGroup has been marked as deleted, and allow the system
// to be sure that a ShardGroup is not simply missing. If the DeletedAt is set, the system can
// safely delete any associated shards.
type ShardGroupInfo struct {
    ID          uint64
    StartTime   time.Time
    EndTime     time.Time
    DeletedAt   time.Time
    Shards      []ShardInfo
    TruncatedAt time.Time
}

ShardInfo 定義：

// ShardInfo represents metadata about a shard.
type ShardInfo struct {
    ID     uint64
    Owners []ShardOwner
}

ShardOwner 定義：

// ShardOwner represents a node that owns a shard.
type ShardOwner struct {
    NodeID uint64
}

ShardOwner主要用於集群，其中NodeId用於標識集群的節點ID，在InfluxDB 1.1社區版本中集群已經不支持了，該欄位無效。

SubscriptionInfo 定義：

// SubscriptionInfo hold the subscription information
type SubscriptionInfo struct {
    Name         string
    Mode         string
    Destinations []string
}

ContinuousQueryInfo 定義：

// ContinuousQueryInfo represents metadata about a continuous query.
type ContinuousQueryInfo struct {
    Name  string
    Query string
}

UserInfo 定義：

// UserInfo represents metadata about a user in the system.
type UserInfo struct {
    Name       string
    Hash       string
    Admin      bool
    Privileges map[string]influxql.Privilege
}

其它

meta文件解析示例代碼：

package main

import (
    "os"
    "fmt"
    "io/ioutil"
    "github.com/influxdata/influxdb/services/meta"
)

func Load(metaFile string) error {
    cacheData:= &meta.Data{
            Index: 1,
        }
    //file := filepath.Join(c.path, metaFile)

    f, err := os.Open(metaFile)
    if err != nil {
        if os.IsNotExist(err) {
            return nil
        }
        return err
    }
    defer f.Close()

    data, err := ioutil.ReadAll(f)
    if err != nil {
        return err
    }

    if err := cacheData.UnmarshalBinary(data); err != nil {
        return err
    }
    //fmt.Println(data)
    //fmt.Println("=======================")

    fmt.Println("Term       :",cacheData.Term)
    fmt.Println("Index      :",cacheData.Index)
    fmt.Println("Databases :")
    //fmt.Println(cacheData.Databases)

    for k,dbInfo := range cacheData.Databases {
        //fmt.Println(k,dbInfo)
        fmt.Println("k =",k)
        fmt.Println(dbInfo.Name,dbInfo.DefaultRetentionPolicy)
        for _,rPolicy := range dbInfo.RetentionPolicies {
            //fmt.Println(rPolicy)
            fmt.Println(rPolicy.Name,rPolicy.ReplicaN,rPolicy.Duration,rPolicy.ShardGroupDuration)
            fmt.Println("-------------ShardGroups---------------")
            //fmt.Println(rPolicy.ShardGroups)
            for shardIdx,shardGroup := range rPolicy.ShardGroups {
                //fmt.Println(shardGroup)
                fmt.Println("shardIdx =",shardIdx)
                fmt.Println("ID          :",shardGroup.ID)
                fmt.Println("StartTime   :",shardGroup.StartTime)
                fmt.Println("EndTime     :",shardGroup.EndTime)
                fmt.Println("DeletedAt   :",shardGroup.DeletedAt)
                //fmt.Println("Shards      :",shardGroup.Shards)
                fmt.Printf("Shards      :")
                for _,shard := range shardGroup.Shards {
                    fmt.Println(shard.ID,shard.Owners)
                }

                fmt.Println("TruncatedAt :",shardGroup.TruncatedAt)
                //fmt.Println(shardGroup.ID,shardGroup.StartTime,shardGroup.EndTime)
                // DeletedAt,Shards  ,      TruncatedAt
            }
            //fmt.Println(rPolicy.Subscriptions)
            fmt.Println("--------------Subscriptions----------------")
            for subsIdx,subInfo := range rPolicy.Subscriptions {
                //fmt.Println(subInfo)
                fmt.Println("subsIdx =",subsIdx)
                fmt.Println("Name :",subInfo.Name)
                fmt.Println("Mode :",subInfo.Mode)
                fmt.Println("Destinations :",subInfo.Destinations)
            }

        }
        fmt.Println("=======================")
    }

    fmt.Println("Users :")
    fmt.Println(cacheData.Users)
    fmt.Println(cacheData.MaxShardGroupID)
    fmt.Println(cacheData.MaxShardID)
    return nil
}

func main() {
    argsWithProg := os.Args
    if(len(argsWithProg) < 2) {
        fmt.Println("usage : ",argsWithProg[0]," configFile")
        return
    }
    metaFile := os.Args[1]

    fmt.Println(argsWithProg)
    fmt.Println(metaFile)

    Load(metaFile)
}

好，就這些了，希望對你有幫助。

本文github地址：

https://github.com/mike-zhang/mikeBlogEssays/blob/master/2018/20180112_InfluxDB_meta文件解析.rst

歡迎補充