ordering

Documentation

Overview

Package ordering is a clientv3 wrapper that caches response header revisions to detect ordering violations from stale responses. Users may define a policy on how to handle the ordering violation, but typically the client should connect to another endpoint and reissue the request.

The most common situation where an ordering violation happens is a client reconnects to a partitioned member and issues a serializable read. Since the partitioned member is likely behind the last member, it may return a Get response based on a store revision older than the store revision used to service a prior Get on the former endpoint.

First, create a client:

cli, err := clientv3.New(clientv3.Config{Endpoints: []string{"localhost:2379"}})
if err != nil {
	// handle error!
}

Next, override the client interface with the ordering wrapper:

vf := func(op clientv3.Op, resp clientv3.OpResponse, prevRev int64) error {
	return fmt.Errorf("ordering: issued %+v, got %+v, expected rev=%v", op, resp, prevRev)
}
cli.KV = ordering.NewKV(cli.KV, vf)

Now calls using 'cli' will reject order violations with an error.

Index

• Variables
• func NewKV(kv clientv3.KV, orderViolationFunc OrderViolationFunc) *kvOrdering
• type OrderViolationFunc
  • func NewOrderViolationSwitchEndpointClosure(c clientv3.Client) OrderViolationFunc

Variables

var ErrNoGreaterRev = errors.New("etcdclient: no cluster members have a revision higher than the previously received revision")

Functions

func NewKV

func NewKV(kv clientv3.KV, orderViolationFunc OrderViolationFunc) *kvOrdering

Types

type OrderViolationFunc

type OrderViolationFunc func(op clientv3.Op, resp clientv3.OpResponse, prevRev int64) error

func NewOrderViolationSwitchEndpointClosure

func NewOrderViolationSwitchEndpointClosure(c clientv3.Client) OrderViolationFunc