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server: Surround sqlite3 transactions with a lock to handle concurrency

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This commit is contained in:
Aaron Lindsay
2013-07-19 22:15:53 -04:00
parent ada1317ec8
commit 24253d2e1e
2 changed files with 25 additions and 11 deletions
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27
server/database.go
View File

@@ -4,9 +4,15 @@ import (
"asink" "asink"
"database/sql" "database/sql"
_ "github.com/mattn/go-sqlite3" _ "github.com/mattn/go-sqlite3"
"sync"
) )
func GetAndInitDB() (*sql.DB, error) { type AsinkDB struct {
db *sql.DB
lock sync.Mutex
}
func GetAndInitDB() (*AsinkDB, error) {
dbLocation := "asink-server.db" //TODO make me configurable dbLocation := "asink-server.db" //TODO make me configurable
db, err := sql.Open("sqlite3", dbLocation) db, err := sql.Open("sqlite3", dbLocation)
@@ -33,11 +39,14 @@ func GetAndInitDB() (*sql.DB, error) {
return nil, err return nil, err
} }
return db, nil ret := new(AsinkDB)
ret.db = db
return ret, nil
} }
func DatabaseAddEvent(db *sql.DB, e *asink.Event) (err error) { func (adb *AsinkDB) DatabaseAddEvent(e *asink.Event) (err error) {
tx, err := db.Begin() adb.lock.Lock()
tx, err := adb.db.Begin()
if err != nil { if err != nil {
return err return err
} }
@@ -47,6 +56,7 @@ func DatabaseAddEvent(db *sql.DB, e *asink.Event) (err error) {
if err != nil { if err != nil {
tx.Rollback() tx.Rollback()
} }
adb.lock.Unlock()
}() }()
result, err := tx.Exec("INSERT INTO events (localid, type, status, path, hash, timestamp, permissions) VALUES (?,?,?,?,?,?,?);", e.LocalId, e.Type, e.Status, e.Path, e.Hash, e.Timestamp, e.Permissions) result, err := tx.Exec("INSERT INTO events (localid, type, status, path, hash, timestamp, permissions) VALUES (?,?,?,?,?,?,?);", e.LocalId, e.Type, e.Status, e.Path, e.Hash, e.Timestamp, e.Permissions)
@@ -67,8 +77,13 @@ func DatabaseAddEvent(db *sql.DB, e *asink.Event) (err error) {
return nil return nil
} }
func DatabaseRetrieveEvents(db *sql.DB, firstId uint64, maxEvents uint) (events []*asink.Event, err error) { func (adb *AsinkDB) DatabaseRetrieveEvents(firstId uint64, maxEvents uint) (events []*asink.Event, err error) {
rows, err := db.Query("SELECT id, localid, type, status, path, hash, timestamp, permissions FROM events WHERE id >= ? ORDER BY id ASC LIMIT ?;", firstId, maxEvents) adb.lock.Lock()
//make sure the database gets unlocked on return
defer func() {
adb.lock.Unlock()
}()
rows, err := adb.db.Query("SELECT id, localid, type, status, path, hash, timestamp, permissions FROM events WHERE id >= ? ORDER BY id ASC LIMIT ?;", firstId, maxEvents)
if err != nil { if err != nil {
return nil, err return nil, err
} }

9
server/server.go
View File

@@ -2,7 +2,6 @@ package main
import ( import (
"asink" "asink"
"database/sql"
"encoding/json" "encoding/json"
"flag" "flag"
"fmt" "fmt"
@@ -15,7 +14,7 @@ import (
//global variables //global variables
var eventsRegexp *regexp.Regexp var eventsRegexp *regexp.Regexp
var port int = 8080 var port int = 8080
var db *sql.DB var adb *AsinkDB
func init() { func init() {
var err error var err error
@@ -26,7 +25,7 @@ func init() {
eventsRegexp = regexp.MustCompile("^/events/([0-9]+)$") eventsRegexp = regexp.MustCompile("^/events/([0-9]+)$")
db, err = GetAndInitDB() adb, err = GetAndInitDB()
if err != nil { if err != nil {
panic(err) panic(err)
} }
@@ -74,7 +73,7 @@ func getEvents(w http.ResponseWriter, r *http.Request, nextEvent uint64) {
w.Write(b) w.Write(b)
}() }()
events, err := DatabaseRetrieveEvents(db, nextEvent, 50) events, err := adb.DatabaseRetrieveEvents(nextEvent, 50)
if err != nil { if err != nil {
panic(err) panic(err)
error_message = err.Error() error_message = err.Error()
@@ -126,7 +125,7 @@ func putEvents(w http.ResponseWriter, r *http.Request) {
return return
} }
for _, event := range events.Events { for _, event := range events.Events {
err = DatabaseAddEvent(db, event) err = adb.DatabaseAddEvent(event)
if err != nil { if err != nil {
//TODO should probably do this in a way that the caller knows how many of these have failed and doesn't re-try sending ones that succeeded //TODO should probably do this in a way that the caller knows how many of these have failed and doesn't re-try sending ones that succeeded
//i.e. add this to the return codes or something //i.e. add this to the return codes or something