gee-rpc/day7 use d.index to mode n to ensure safety

geektutu · Oct 6, 2020 · b5646b6 · b5646b6
1 parent 57e2881
commit b5646b6
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Showing 2 changed files with 7 additions and 4 deletions.
diff --git a/gee-rpc/day7-registry/registry/registry.go b/gee-rpc/day7-registry/registry/registry.go
@@ -3,6 +3,7 @@ package registy
 import (
  "log"
  "net/http"
+ "sort"
  "strings"
  "sync"
  "time"
@@ -54,6 +55,7 @@ func (r *Registry) aliveServers() []string {
  delete(r.servers, addr)
  }
  }
+ sort.Strings(alive)
  return alive
 }
 

diff --git a/gee-rpc/day7-registry/xclient/discovery.go b/gee-rpc/day7-registry/xclient/discovery.go
@@ -49,15 +49,16 @@ func (d *MultiServersDiscovery) Update(servers []string) error {
 func (d *MultiServersDiscovery) Get(mode SelectMode) (string, error) {
  d.mu.Lock()
  defer d.mu.Unlock()
- if len(d.servers) == 0 {
+ n := len(d.servers)
+ if n == 0 {
  return "", errors.New("rpc discovery: no available servers")
  }
  switch mode {
  case RandomSelect:
- return d.servers[d.r.Intn(len(d.servers))], nil
+ return d.servers[d.r.Intn(n)], nil
  case RoundRobinSelect:
- s := d.servers[d.index]
- d.index = (d.index + 1) % len(d.servers)
+ s := d.servers[d.index%n] // servers could be updated, so mode n to ensure safety
+ d.index = (d.index + 1) % n
  return s, nil
  default:
  return "", errors.New("rpc discovery: not supported select mode")