sort keys so output is deterministic

- separate buildRequest method
- increase timeout for cancel context test

internals/overlord/logstate/loki.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"sort"
 	"strconv"
 	"strings"
 
@@ -70,24 +71,9 @@ func (c *lokiClient) Flush(ctx context.Context) error {
 	if c.numEntries() == 0 {
 		return nil // no-op
 	}
-
 	defer c.emptyBuffer()
 
-	// Build request
-	req := lokiRequest{}
-	for service, entries := range c.entries {
-		if len(entries) == 0 {
-			continue
-		}
-		stream := lokiStream{
-			Labels: map[string]string{
-				"pebble_service": service,
-			},
-			Entries: entries,
-		}
-		req.Streams = append(req.Streams, stream)
-	}
-
+	req := c.buildRequest()
 	jsonReq, err := json.Marshal(req)
 	if err != nil {
 		return fmt.Errorf("encoding request to JSON: %v", err)
@@ -119,6 +105,31 @@ func (c *lokiClient) Flush(ctx context.Context) error {
 	return nil
 }
 
+func (c *lokiClient) buildRequest() (req lokiRequest) {
+	// Sort keys to guarantee deterministic output
+	var services []string
+	for svc, entries := range c.entries {
+		if len(entries) == 0 {
+			delete(c.entries, svc)
+			continue
+		}
+		services = append(services, svc)
+	}
+	sort.Strings(services)
+
+	for _, service := range services {
+		entries := c.entries[service]
+		stream := lokiStream{
+			Labels: map[string]string{
+				"pebble_service": service,
+			},
+			Entries: entries,
+		}
+		req.Streams = append(req.Streams, stream)
+	}
+	return
+}
+
 func (c *lokiClient) emptyBuffer() {
 	for svc := range c.entries {
 		c.entries[svc] = c.entries[svc][:0]

internals/overlord/logstate/loki_test.go

@@ -144,7 +144,7 @@ func (*lokiSuite) TestLokiFlushCancelContext(c *C) {
 	c.Assert(err, IsNil)
 
 	// Cancel the Flush context quickly
-	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Millisecond)
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Microsecond)
 	defer cancel()
 
 	flushReturned := make(chan struct{})
@@ -157,7 +157,7 @@ func (*lokiSuite) TestLokiFlushCancelContext(c *C) {
 	// Check Flush returns quickly after context timeout
 	select {
 	case <-flushReturned:
-	case <-time.After(2 * time.Millisecond):
+	case <-time.After(20 * time.Millisecond):
 		c.Fatal("lokiClient.Flush took too long to return after context timeout")
 	}
 }