Fix race condition

2 files changed, 26 insertions, 0 deletions

diff --git a/sql/sql.go b/sql/sql.go
index 76f8417..45d969b 100644
--- a/sql/sql.go
+++ b/sql/sql.go
@@ -79,6 +79,8 @@ func New(filename string) (*Client, error) {
 
 // ReadLog reads the n most recent entries from the log.
 func (c *Client) ReadLog(n int) ([]LogEntry, error) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
 	query := `
 SELECT time,
        type,
diff --git a/sql/sql_test.go b/sql/sql_test.go
index a6e4fb3..f7a7432 100644
--- a/sql/sql_test.go
+++ b/sql/sql_test.go
@@ -2,6 +2,7 @@ package sql
 
 import (
 	"reflect"
+	"sync"
 	"testing"
 	"time"
 )
@@ -117,3 +118,26 @@ func TestDeleteLogBefore(t *testing.T) {
 		t.Errorf("got %d rows for answer %q, want %d", got, question, want)
 	}
 }
+
+func TestInterleavedRW(t *testing.T) {
+	c := testClient()
+	var wg sync.WaitGroup
+	wg.Add(1)
+	ch := make(chan bool, 10)
+	var err error
+	go func() {
+		defer wg.Done()
+		for range ch {
+			err = c.WriteLog(time.Now(), 1, "example.com.", "192.0.2.1")
+		}
+	}()
+	ch <- true
+	close(ch)
+	if _, err := c.ReadLog(1); err != nil {
+		t.Fatal(err)
+	}
+	wg.Wait()
+	if err != nil {
+		t.Fatal(err)
+	}
+}