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Simplify GetToken synchronization #21162

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merged 1 commit into from
Jul 13, 2023
Merged

Simplify GetToken synchronization #21162

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36 changes: 9 additions & 27 deletions sdk/azidentity/syncer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,16 +23,15 @@ type authFn func(context.Context, policy.TokenRequestOptions) (azcore.AccessToke
// syncer synchronizes authentication calls so that goroutines can share a credential instance
type syncer struct {
addlTenants []string
authing bool
cond *sync.Cond
mu *sync.Mutex
reqToken, silent authFn
name, tenant string
}

func newSyncer(name, tenant string, additionalTenants []string, reqToken, silentAuth authFn) *syncer {
return &syncer{
addlTenants: resolveAdditionalTenants(additionalTenants),
cond: &sync.Cond{L: &sync.Mutex{}},
mu: &sync.Mutex{},
name: name,
reqToken: reqToken,
silent: silentAuth,
Expand All @@ -42,40 +41,23 @@ func newSyncer(name, tenant string, additionalTenants []string, reqToken, silent

// GetToken ensures that only one goroutine authenticates at a time
func (s *syncer) GetToken(ctx context.Context, opts policy.TokenRequestOptions) (azcore.AccessToken, error) {
var at azcore.AccessToken
var err error
s.mu.Lock()
defer s.mu.Unlock()
if len(opts.Scopes) == 0 {
return at, errors.New(s.name + ".GetToken() requires at least one scope")
return azcore.AccessToken{}, errors.New(s.name + ".GetToken() requires at least one scope")
}
// we don't resolve the tenant for managed identities because they can acquire tokens only from their home tenants
if s.name != credNameManagedIdentity {
tenant, err := s.resolveTenant(opts.TenantID)
if err != nil {
return at, err
return azcore.AccessToken{}, err
}
opts.TenantID = tenant
}
auth := false
s.cond.L.Lock()
defer s.cond.L.Unlock()
for {
at, err = s.silent(ctx, opts)
if err == nil {
// got a token
break
}
if !s.authing {
// this goroutine will request a token
s.authing, auth = true, true
break
}
// another goroutine is acquiring a token; wait for it to finish, then try silent auth again
s.cond.Wait()
}
if auth {
s.authing = false
at, err := s.silent(ctx, opts)
if err != nil {
// cache miss; request a new token
at, err = s.reqToken(ctx, opts)
s.cond.Broadcast()
}
if err != nil {
// Return credentialUnavailableError directly because that type affects the behavior of credential chains.
Expand Down