/
store.go
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/
store.go
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// Copyright 2022 Ed Huang<i@huangdx.net>
//
// 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 tipubsub
import (
"database/sql"
"fmt"
"time"
_ "github.com/go-sql-driver/mysql"
)
// Store is the interface for the storage of the messages
type Store interface {
// Init initializes the store, call it after creating the store
Init() error
// CreateStream creates a stream
CreateStream(streamName string) error
// PutMessages puts messages into a stream
PutMessages(streamName string, messages []*Message) error
// FetchMessages fetches messages from a stream
FetchMessages(streamName string, offset Offset, limit int) ([]Message, Offset, error)
// MinMaxID returns the min, max offset of a stream
MinMaxID(streamName string) (int64, int64, error)
// GetStreamNames returns the names of all streams
GetStreamNames() ([]string, error)
// DB returns the underlying database
DB() *sql.DB
}
func OpenStore(dsn string) (Store, error) {
s := NewTiDBStore(dsn)
if err := s.Init(); err != nil {
return nil, err
}
return s, nil
}
type TiDBStore struct {
dsn string
db *sql.DB
}
func getStreamTblName(streamName string) string {
return fmt.Sprintf("tipubsub_stream_%s", streamName)
}
func (s *TiDBStore) getMetaTblName(streamName string) string {
return fmt.Sprintf("tipubsub_meta_%s", streamName)
}
func NewTiDBStore(dsn string) *TiDBStore {
return &TiDBStore{
dsn: dsn,
}
}
func (s *TiDBStore) GetStreamNames() ([]string, error) {
var names []string
rows, err := s.db.Query("SELECT stream_name FROM tipubsub_meta")
if err != nil {
return nil, err
}
defer rows.Close()
for rows.Next() {
var name string
err := rows.Scan(&name)
if err != nil {
return nil, err
}
names = append(names, name)
}
return names, nil
}
// CreateStream creates a stream, every stream is a table in the database
func (s *TiDBStore) CreateStream(streamName string) error {
// stream is a table in the database
stmt := fmt.Sprintf(`
CREATE TABLE IF NOT EXISTS %s (
id BIGINT AUTO_INCREMENT,
ts BIGINT,
create_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
data TEXT,
PRIMARY KEY (id),
KEY(ts)
);`, getStreamTblName(streamName))
_, err := s.db.Exec(stmt)
if err != nil {
return err
}
// insert the stream name into the meta table
stmt = fmt.Sprintf(`
REPLACE INTO tipubsub_meta (stream_name)
VALUES ('%s');`, streamName)
_, err = s.db.Exec(stmt)
if err != nil {
return err
}
return nil
}
func (s *TiDBStore) Init() error {
var err error
s.db, err = sql.Open("mysql", s.dsn)
if err != nil {
return err
}
// default connection timeout setting
// application could customize it
// by using the value return of DB()
s.db.SetConnMaxLifetime(time.Minute * 3)
s.db.SetMaxOpenConns(50)
s.db.SetMaxIdleConns(50)
// create stream meta table for all the streams
stmt := fmt.Sprintf(`
CREATE TABLE IF NOT EXISTS tipubsub_meta (
stream_name VARCHAR(255) NOT NULL UNIQUE KEY
);`)
_, err = s.db.Exec(stmt)
if err != nil {
return err
}
return nil
}
func (s *TiDBStore) PutMessages(streamName string, messages []*Message) error {
// a message is a row in the table, so we need to use a transaction
// because auto_increment is used, we don't need to set id
// use id as the offset
txn, err := s.db.Begin()
defer txn.Rollback()
if err != nil {
return err
}
for _, msg := range messages {
sql := fmt.Sprintf(`
INSERT INTO %s (
ts,
data
) VALUES (
?,
?
)`, getStreamTblName(streamName))
res, err := txn.Exec(sql, msg.Ts, msg.Data)
if err != nil {
return err
}
id, err := res.LastInsertId()
if err != nil {
return err
}
msg.ID = id
}
err = txn.Commit()
if err != nil {
return err
}
return nil
}
func (s *TiDBStore) FetchMessages(streamName string, idOffset Offset, limit int) ([]Message, Offset, error) {
if idOffset == LatestId {
_, maxOffset, err := s.MinMaxID(streamName)
if err != nil {
return nil, 0, err
}
idOffset = Offset(maxOffset)
}
stmt := fmt.Sprintf(`
SELECT
id,
ts,
data
FROM %s
WHERE id > ?
LIMIT %d`, getStreamTblName(streamName), limit)
rows, err := s.db.Query(stmt, idOffset)
if err != nil {
if err == sql.ErrNoRows {
return nil, 0, nil
}
return nil, 0, err
}
defer rows.Close()
var messages []Message
var maxId int64 = 0
for rows.Next() {
var id int64
var ts int64
var data string
err := rows.Scan(&id, &ts, &data)
if err != nil {
return nil, 0, err
}
messages = append(messages, Message{
ID: id,
Ts: ts,
Data: data,
})
if id > maxId {
maxId = id
}
}
return messages, Offset(maxId), nil
}
func (s *TiDBStore) MinMaxID(streamName string) (int64, int64, error) {
// using isnull make sure when there is no message in the stream, not return NULL
stmt := fmt.Sprintf(`
SELECT
IFNULL(MIN(id), 0),
IFNULL(MAX(id), 0)
FROM %s`, getStreamTblName(streamName))
var minId, maxId int64
err := s.db.QueryRow(stmt).Scan(&minId, &maxId)
if err != nil {
return -1, -1, err
}
return minId, maxId, nil
}
func (s *TiDBStore) DB() *sql.DB {
return s.db
}