137 lines
3.0 KiB
Go
137 lines
3.0 KiB
Go
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package discovery
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import (
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"errors"
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"fmt"
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"path"
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"sort"
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"strconv"
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"strings"
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"github.com/coreos/etcd/client"
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"github.com/coreos/etcd/etcdserver/etcdhttp"
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)
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var (
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ErrInvalidURL = errors.New("discovery: invalid URL")
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ErrBadCluster = errors.New("discovery: bad key/value inside cluster")
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ErrSizeNotFound = errors.New("discovery: size key not found")
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ErrTokenNotFound = errors.New("discovery: token not found")
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ErrDuplicateID = errors.New("discovery: found duplicate id")
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ErrFullCluster = errors.New("discovery: cluster is full")
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)
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type discovery struct {
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cluster string
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id int64
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ctx []byte
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c client.Client
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}
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func (d *discovery) discover() (*etcdhttp.Peers, error) {
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if err := d.createSelf(); err != nil {
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return nil, err
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}
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nodes, size, err := d.checkCluster()
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if err != nil {
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return nil, err
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}
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all, err := d.waitNodes(nodes, size)
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if err != nil {
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return nil, err
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}
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return nodesToPeers(all)
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}
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func (d *discovery) createSelf() error {
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self := path.Join("/", d.cluster, fmt.Sprintf("%d", d.id))
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// create self key
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resp, err := d.c.Create(self, string(d.ctx), 0)
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if err != nil {
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return err
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}
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// ensure self appears on the server we connected to
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w := d.c.Watch(self, resp.Node.CreatedIndex)
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if _, err = w.Next(); err != nil {
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return err
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}
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return nil
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}
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func (d *discovery) checkCluster() (client.Nodes, int, error) {
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self := path.Join("/", d.cluster, fmt.Sprintf("%d", d.id))
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resp, err := d.c.Get(d.cluster)
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if err != nil {
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return nil, 0, err
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}
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nodes := resp.Node.Nodes
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snodes := SortableNodes{nodes}
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sort.Sort(snodes)
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// find cluster size
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if nodes[0].Key != path.Join("/", d.cluster, "size") {
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return nil, 0, ErrSizeNotFound
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}
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size, err := strconv.Atoi(nodes[0].Value)
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if err != nil {
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return nil, 0, ErrBadCluster
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}
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// remove size key from nodes
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nodes = nodes[1:]
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// find self position
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for i := range nodes {
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if nodes[i].Key == self {
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break
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}
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if i >= size-1 {
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return nil, size, ErrFullCluster
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}
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}
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return nodes, size, nil
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}
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func (d *discovery) waitNodes(nodes client.Nodes, size int) (client.Nodes, error) {
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if len(nodes) > size {
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nodes = nodes[:size]
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}
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w := d.c.RecursiveWatch(d.cluster, nodes[len(nodes)-1].ModifiedIndex)
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all := make(client.Nodes, len(nodes))
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copy(all, nodes)
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// wait for others
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for len(all) < size {
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resp, err := w.Next()
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if err != nil {
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return nil, err
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}
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all = append(all, resp.Node)
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}
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return all, nil
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}
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func nodesToPeers(ns client.Nodes) (*etcdhttp.Peers, error) {
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s := make([]string, len(ns))
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for i, n := range ns {
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s[i] = n.Value
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}
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var peers etcdhttp.Peers
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if err := peers.Set(strings.Join(s, "&")); err != nil {
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return nil, err
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}
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return &peers, nil
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}
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type SortableNodes struct{ client.Nodes }
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func (ns SortableNodes) Len() int { return len(ns.Nodes) }
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func (ns SortableNodes) Less(i, j int) bool {
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return ns.Nodes[i].CreatedIndex < ns.Nodes[j].CreatedIndex
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}
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func (ns SortableNodes) Swap(i, j int) { ns.Nodes[i], ns.Nodes[j] = ns.Nodes[j], ns.Nodes[i] }
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