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datastore.go
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datastore.go
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package datastore
import (
"fmt"
"io/ioutil"
"lib/serial"
"net"
"os"
"strconv"
"sync"
)
//go:generate counterfeiter -o ../fakes/locker.go --fake-name Locker . locker
type locker interface {
Lock() error
Unlock() error
}
//go:generate counterfeiter -o ../fakes/datastore.go --fake-name Datastore . Datastore
type Datastore interface {
Add(handle, ip string, metadata map[string]interface{}) error
Delete(handle string) (Container, error)
ReadAll() (map[string]Container, error)
}
type Container struct {
Handle string `json:"handle"`
IP string `json:"ip"`
Metadata map[string]interface{} `json:"metadata"`
}
type Store struct {
Serializer serial.Serializer
Locker locker
DataFilePath string
VersionFilePath string
CacheMutex *sync.RWMutex
cachedVersion int
cachedPool map[string]Container
}
func validate(handle, ip string) error {
if handle == "" {
return fmt.Errorf("invalid handle")
}
if net.ParseIP(ip) == nil {
return fmt.Errorf("invalid ip: %v", ip)
}
return nil
}
func (c *Store) Add(handle, ip string, metadata map[string]interface{}) error {
if err := validate(handle, ip); err != nil {
return err
}
err := c.Locker.Lock()
if err != nil {
return fmt.Errorf("lock: %s", err)
}
defer c.Locker.Unlock()
dataFile, err := os.OpenFile(c.DataFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0600)
if err != nil {
return fmt.Errorf("open data file: %s", err)
}
defer dataFile.Close()
pool := make(map[string]Container)
err = c.Serializer.DecodeAll(dataFile, &pool)
if err != nil {
return fmt.Errorf("decoding file: %s", err)
}
pool[handle] = Container{
Handle: handle,
IP: ip,
Metadata: metadata,
}
err = c.Serializer.EncodeAndOverwrite(dataFile, pool)
if err != nil {
return fmt.Errorf("encode and overwrite: %s", err)
}
err = c.updateVersion()
if err != nil {
return err
}
return nil
}
func (c *Store) Delete(handle string) (Container, error) {
deleted := Container{}
if handle == "" {
return deleted, fmt.Errorf("invalid handle")
}
err := c.Locker.Lock()
if err != nil {
return deleted, fmt.Errorf("lock: %s", err)
}
defer c.Locker.Unlock()
dataFile, err := os.OpenFile(c.DataFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0600)
if err != nil {
return deleted, fmt.Errorf("open data file: %s", err)
}
defer dataFile.Close()
pool := make(map[string]Container)
err = c.Serializer.DecodeAll(dataFile, &pool)
if err != nil {
return deleted, fmt.Errorf("decoding file: %s", err)
}
deleted = pool[handle]
delete(pool, handle)
err = c.Serializer.EncodeAndOverwrite(dataFile, pool)
if err != nil {
return deleted, fmt.Errorf("encode and overwrite: %s", err)
}
err = c.updateVersion()
if err != nil {
return deleted, err
}
return deleted, nil
}
func (c *Store) ReadAll() (map[string]Container, error) {
currentVersion, err := c.currentVersion()
if err != nil {
return nil, err
}
c.CacheMutex.RLock()
if currentVersion == c.cachedVersion {
pool := c.cachedPool
c.CacheMutex.RUnlock()
return pool, nil
}
c.CacheMutex.RUnlock()
err = c.Locker.Lock()
if err != nil {
return nil, fmt.Errorf("lock: %s", err)
}
defer c.Locker.Unlock()
dataFile, err := os.OpenFile(c.DataFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0600)
if err != nil {
return nil, fmt.Errorf("open data file: %s", err)
}
defer dataFile.Close()
pool := make(map[string]Container)
err = c.Serializer.DecodeAll(dataFile, &pool)
if err != nil {
return nil, fmt.Errorf("decoding file: %s", err)
}
// untested
// we want to get the version again while we have the store locked
currentVersion, err = c.currentVersion()
if err != nil {
return nil, err
}
c.CacheMutex.Lock()
defer c.CacheMutex.Unlock()
c.cachedPool = pool
c.cachedVersion = currentVersion
return pool, nil
}
func (c *Store) updateVersion() error {
version, err := c.currentVersion()
if err != nil {
return err
}
err = ioutil.WriteFile(c.VersionFilePath, []byte(strconv.Itoa(version+1)), os.ModePerm)
if err != nil {
// not tested
return fmt.Errorf("write version file: %s", err)
}
return nil
}
func (c *Store) currentVersion() (int, error) {
version := 1
versionFile, err := os.OpenFile(c.VersionFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0600)
if err != nil {
return version, fmt.Errorf("open version file: %s", err)
}
defer versionFile.Close()
versionContents, err := ioutil.ReadAll(versionFile)
if err != nil {
// not tested
return version, fmt.Errorf("open version file: %s", err)
}
if string(versionContents) != "" {
version, err = strconv.Atoi(string(versionContents))
if err != nil {
return version, fmt.Errorf("version file: '%s' is not a number", versionContents)
}
}
return version, err
}