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client.go
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client.go
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/*
* Copyright 2019 The Vitess Authors.
* 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.
*/
// client.go is a sample for using the Vitess Go SQL driver.
//
// Before running this, start up a local example cluster as described in the
// README.md file.
//
// Then run:
// vitess$ . dev.env
// vitess$ cd examples/local
// vitess/examples/local$ go run client.go -server=localhost:15991
package main
import (
"flag"
"fmt"
"math/rand"
"os"
"time"
"vitess.io/vitess/go/vt/vitessdriver"
)
var (
server = flag.String("server", "", "vtgate server to connect to")
)
func main() {
flag.Parse()
rand.Seed(time.Now().UnixNano())
// Connect to vtgate.
db, err := vitessdriver.Open(*server, "@master")
if err != nil {
fmt.Printf("client error: %v\n", err)
os.Exit(1)
}
defer db.Close()
// Insert some messages on random pages.
fmt.Println("Inserting into master...")
for i := 0; i < 3; i++ {
tx, err := db.Begin()
if err != nil {
fmt.Printf("begin failed: %v\n", err)
os.Exit(1)
}
page := rand.Intn(100) + 1
timeCreated := time.Now().UnixNano()
if _, err := tx.Exec("INSERT INTO messages (page,time_created_ns,message) VALUES (?,?,?)",
page, timeCreated, "V is for speed"); err != nil {
fmt.Printf("exec failed: %v\n", err)
os.Exit(1)
}
if err := tx.Commit(); err != nil {
fmt.Printf("commit failed: %v\n", err)
os.Exit(1)
}
}
// Read it back from the master.
fmt.Println("Reading from master...")
rows, err := db.Query("SELECT page, time_created_ns, message FROM messages")
if err != nil {
fmt.Printf("query failed: %v\n", err)
os.Exit(1)
}
for rows.Next() {
var page, timeCreated uint64
var msg string
if err := rows.Scan(&page, &timeCreated, &msg); err != nil {
fmt.Printf("scan failed: %v\n", err)
os.Exit(1)
}
fmt.Printf("(%v, %v, %q)\n", page, timeCreated, msg)
}
if err := rows.Err(); err != nil {
fmt.Printf("row iteration failed: %v\n", err)
os.Exit(1)
}
// Read from a replica.
// Note that this may be behind master due to replication lag.
fmt.Println("Reading from replica...")
dbr, err := vitessdriver.Open(*server, "@replica")
if err != nil {
fmt.Printf("client error: %v\n", err)
os.Exit(1)
}
defer dbr.Close()
rows, err = dbr.Query("SELECT page, time_created_ns, message FROM messages")
if err != nil {
fmt.Printf("query failed: %v\n", err)
os.Exit(1)
}
for rows.Next() {
var page, timeCreated uint64
var msg string
if err := rows.Scan(&page, &timeCreated, &msg); err != nil {
fmt.Printf("scan failed: %v\n", err)
os.Exit(1)
}
fmt.Printf("(%v, %v, %q)\n", page, timeCreated, msg)
}
if err := rows.Err(); err != nil {
fmt.Printf("row iteration failed: %v\n", err)
os.Exit(1)
}
}