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liteq.go
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liteq.go
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package liteq
import (
"database/sql"
"fmt"
"strings"
"sync"
"time"
"github.com/lateefj/gq"
// sqlite3 database package impoart
_ "github.com/mattn/go-sqlite3"
)
// TimeWithMsSqlite ... Special constant to get a time with milliseconds. This is helpful for checkout as the timeout might be sub second
const TimeWithMsSqlite = "STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW')"
var (
createSchema = `
CREATE TABLE IF NOT EXISTS %sq (
id INTEGER PRIMARY KEY AUTOINCREMENT,
timestamp TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
checkout TIMESTAMP,
payload BLOB
);
CREATE INDEX IF NOT EXISTS %sq_timestamp_idx ON %sq (checkout ASC, timestamp ASC);
`
dropScrema = `
DROP TABLE IF EXISTS %sq;
`
)
// Liteq Structure for sqlite
type Liteq struct {
DB *sql.DB
Prefix string
TTL time.Duration
exit bool
mutex *sync.RWMutex
}
// Create ... builds any required tables
func (l *Liteq) Create() error {
if l.mutex == nil {
l.mutex = &sync.RWMutex{}
}
s := fmt.Sprintf(createSchema, l.Prefix, l.Prefix, l.Prefix)
_, err := l.DB.Exec(s)
return err
}
// Destroy ... removes any tables
func (l *Liteq) Destroy() error {
s := fmt.Sprintf(dropScrema, l.Prefix)
_, err := l.DB.Exec(s)
return err
}
// StopConsumer ... Stop consuming messages
func (l *Liteq) StopConsumer() {
l.mutex.Lock()
l.exit = true
l.mutex.Unlock()
}
// Exit ...
func (l *Liteq) Exit() bool {
l.mutex.RLock()
defer l.mutex.RUnlock()
return l.exit
}
// Publish ... This pushes a list of messages into the DB
func (l *Liteq) Publish(messages []*gq.Message) error {
txn, err := l.DB.Begin()
defer txn.Commit()
if err != nil {
return err
}
q := fmt.Sprintf("INSERT INTO %sq (payload) VALUES(?);", l.Prefix)
stmt, err := txn.Prepare(q)
if err != nil {
return err
}
defer stmt.Close()
for _, m := range messages {
_, err := stmt.Exec(m.Payload)
if err != nil {
return err
}
}
return err
}
// Commit ... Removes any messages that bave been comsusumed by the b
func (l *Liteq) Commit(recipts []*gq.Receipt) error {
deleteQuery := fmt.Sprintf("DELETE FROM %sq WHERE id IN(?)", l.Prefix)
deleteStmt, err := l.DB.Prepare(deleteQuery)
if err != nil {
return err
}
defer deleteStmt.Close()
deleteIds := make([]int64, 0)
for _, r := range recipts {
if r.Success {
deleteIds = append(deleteIds, r.Id)
}
}
deleteClause := strings.Trim(strings.Replace(fmt.Sprint(deleteIds), " ", ",", -1), "[]")
_, err = deleteStmt.Exec(deleteClause)
return err
}
// ConsumeBatch ... This consumes a number of messages up to the limit
func (l *Liteq) ConsumeBatch(size int) ([]*gq.ConsumerMessage, error) {
ms := make([]*gq.ConsumerMessage, 0)
// Find
q := fmt.Sprintf("SELECT id, payload FROM %sq WHERE checkout IS null", l.Prefix)
// If there is a TTL then checkout messages that have expired
if l.TTL.Seconds() > 0.0 {
q = fmt.Sprintf("%s OR DATETIME(checkout, '%f second') < %s", q, l.TTL.Seconds(), TimeWithMsSqlite)
}
// Order and limit
q = fmt.Sprintf("%s ORDER BY checkout ASC, timestamp ASC LIMIT $1;", q)
txn, err := l.DB.Begin()
if err != nil {
return ms, err
}
defer txn.Commit()
stmt, err := l.DB.Prepare(q)
if err != nil {
return ms, err
}
defer stmt.Close()
var rows *sql.Rows
rows, err = stmt.Query(size)
if err != nil {
return ms, err
}
checkoutIds := make([]int64, 0)
defer rows.Close()
for rows.Next() {
var id int64
var payload []byte
rows.Scan(&id, &payload)
checkoutIds = append(checkoutIds, id)
ms = append(ms, &gq.ConsumerMessage{Message: gq.Message{Payload: payload}, Id: id})
}
// Query any messages that have not been checked out
uq := fmt.Sprintf("UPDATE %sq SET checkout = %s WHERE id IN (?);", l.Prefix, TimeWithMsSqlite)
update, err := l.DB.Prepare(uq)
if err != nil {
return ms, err
}
checkoutClause := strings.Trim(strings.Replace(fmt.Sprint(checkoutIds), " ", ",", -1), "[]")
_, err = update.Exec(checkoutClause)
if err != nil {
txn.Rollback()
return nil, err
}
defer stmt.Close()
return ms, nil
}
// Stream ... Creates a stream of consumption
func (l *Liteq) Stream(size int, messages chan []*gq.ConsumerMessage, pause time.Duration) {
defer close(messages)
for {
// Consume until there are no more messages or there is an error
// No messages there was an error or time to exit
for {
if l.Exit() {
return
}
ms, err := l.ConsumeBatch(size)
// If exit then
if len(ms) == 0 || err != nil {
break
}
messages <- ms
}
// Breather so not just infinate loop of queries
time.Sleep(pause)
}
}