feat (ldap): add worker pool for LDAP token group lookups

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 Canonical reference for changes, improvements, and bugfixes for cap.
 
+## Next
+
+* LDAP
+  * Add worker pool for LDAP token group lookups ([**PR**](https://github.com/hashicorp/cap/pull/98))
+
 ## 0.3.4
 
 ### Bug fixes

ldap/client.go

@@ -15,6 +15,7 @@ import (
 	"net"
 	"net/url"
 	"strings"
+	"sync"
 	"text/template"
 	"time"
 
@@ -458,35 +459,63 @@ func (c *Client) tokenGroupsSearch(userDN string) ([]*ldap.Entry, []Warning, err
 
 	userEntry := result.Entries[0]
 	groupAttrValues := userEntry.GetRawAttributeValues("tokenGroups")
-
 	groupEntries := make([]*ldap.Entry, 0, len(groupAttrValues))
-	for _, sidBytes := range groupAttrValues {
-		sidString, err := sidBytesToString(sidBytes)
-		if err != nil {
-			warnings = append(warnings, fmtWarning("%s: unable to read sid: %s", op, err.Error()))
-			continue
-		}
 
-		groupResult, err := c.conn.Search(&ldap.SearchRequest{
-			BaseDN:       fmt.Sprintf("<SID=%s>", sidString),
-			Scope:        ldap.ScopeBaseObject,
-			DerefAliases: derefAliasMap[c.conf.DerefAliases],
-			Filter:       "(objectClass=*)",
-			Attributes: []string{
-				"1.1", // RFC no attributes
-			},
-			SizeLimit: 1,
-		})
-		if err != nil {
-			warnings = append(warnings, fmtWarning("%s: unable to read the group sid (baseDN: %q / filter: %q): %s", op, fmt.Sprintf("<SID=%s>", sidString), "(objectClass=*)", sidString))
-			continue
+	{
+		// we're using worker pool to make looking up token groups more
+		// performant.  token groups have to be looked up individually, so if a
+		// user is a member of MANY groups it can be helpful to do these lookups
+		// concurrently vs serially. This is based on benchmarks and a
+		// subsequent implementation within vault's codebase for looking up token
+		// groups. See: https://github.com/hashicorp/vault/pull/22659
+		const maxWorkers = 10
+		var wg sync.WaitGroup
+		var lock sync.Mutex
+		taskChan := make(chan string) // intentionally an unbuffered chan so we can iterate (range) over it before it's closed.
+		for i := 0; i < maxWorkers; i++ {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				for sidString := range taskChan {
+					groupResult, err := c.conn.Search(&ldap.SearchRequest{
+						BaseDN:       fmt.Sprintf("<SID=%s>", sidString),
+						Scope:        ldap.ScopeBaseObject,
+						DerefAliases: derefAliasMap[c.conf.DerefAliases],
+						Filter:       "(objectClass=*)",
+						Attributes: []string{
+							"1.1", // RFC no attributes
+						},
+						SizeLimit: 1,
+					})
+					if err != nil {
+						warnings = append(warnings, fmtWarning("%s: unable to read the group sid (baseDN: %q / filter: %q): %s", op, fmt.Sprintf("<SID=%s>", sidString), "(objectClass=*)", sidString))
+						continue
+					}
+					if len(groupResult.Entries) == 0 {
+						warnings = append(warnings, fmtWarning("%s: unable to find the group sid (baseDN: %q / filter: %q): %s", op, fmt.Sprintf("<SID=%s>", sidString), "(objectClass=*)", sidString))
+						continue
+					}
+					lock.Lock()
+					groupEntries = append(groupEntries, groupResult.Entries[0])
+					lock.Unlock()
+				}
+			}()
 		}
-		if len(groupResult.Entries) == 0 {
-			warnings = append(warnings, fmtWarning("%s: unable to find the group sid (baseDN: %q / filter: %q): %s", op, fmt.Sprintf("<SID=%s>", sidString), "(objectClass=*)", sidString))
-			continue
+		for _, sidBytes := range groupAttrValues {
+			sidString, err := sidBytesToString(sidBytes)
+			if err != nil {
+				warnings = append(warnings, fmtWarning("%s: unable to read sid: %s", op, err.Error()))
+				continue
+			}
+			taskChan <- sidString
 		}
+		// closing the taskChan will allow the workers to start iterating
+		// (range) - this unblocks them
+		close(taskChan)
 
-		groupEntries = append(groupEntries, groupResult.Entries[0])
+		// wait for all the workers to finish up the token group lookups and
+		// adding all the groups to the slice of group entries
+		wg.Wait()
 	}
 
 	return groupEntries, warnings, nil