clientv3util

Documentation

Overview

Package clientv3util contains utility functions derived from clientv3.

Index

• func KeyExists(key string) clientv3.Cmp
• func KeyMissing(key string) clientv3.Cmp

Examples

• KeyExists
• KeyMissing

Functions

func KeyExists

func KeyExists(key string) clientv3.Cmp

KeyExists returns a comparison operation that evaluates to true iff the given key exists. It does this by checking if the key `Version` is greater than 0. It is a useful guard in transaction delete operations.

Example

cli, err := clientv3.New(clientv3.Config{
	Endpoints: []string{"127.0.0.1:2379"},
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()
kvc := clientv3.NewKV(cli)

// perform a delete only if key already exists
_, err = kvc.Txn(context.Background()).
	If(clientv3util.KeyExists("purpleidea")).
	Then(clientv3.OpDelete("purpleidea")).
	Commit()
if err != nil {
	log.Fatal(err)
}

func KeyMissing

func KeyMissing(key string) clientv3.Cmp

KeyMissing returns a comparison operation that evaluates to true iff the given key does not exist.

Example

cli, err := clientv3.New(clientv3.Config{
	Endpoints: []string{"127.0.0.1:2379"},
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()
kvc := clientv3.NewKV(cli)

// perform a put only if key is missing
// It is useful to do the check atomically to avoid overwriting
// the existing key which would generate potentially unwanted events,
// unless of course you wanted to do an overwrite no matter what.
_, err = kvc.Txn(context.Background()).
	If(clientv3util.KeyMissing("purpleidea")).
	Then(clientv3.OpPut("purpleidea", "hello world")).
	Commit()
if err != nil {
	log.Fatal(err)
}