feat(logfwd): support forwarding logs to Loki

internals/overlord/logstate/loki/export_test.go

@@ -0,0 +1,25 @@
+// Copyright (c) 2023 Canonical Ltd
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 3 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package loki
+
+type LokiEntryWithService = lokiEntryWithService
+
+func GetBuffer(c *Client) []LokiEntryWithService {
+	return c.buffer
+}
+
+func GetMessage(e LokiEntryWithService) string {
+	return e.entry[1]
+}

internals/overlord/logstate/loki/loki_test.go

@@ -191,6 +191,65 @@ func (*suite) TestServerTimeout(c *C) {
 	c.Assert(err, ErrorMatches, ".*context deadline exceeded.*")
 }
 
+func (*suite) TestBufferFull(c *C) {
+	client := loki.NewClientWithOptions(
+		&plan.LogTarget{
+			Name:     "tgt1",
+			Location: "fake",
+		},
+		&loki.ClientOptions{
+			MaxRequestEntries: 3,
+		},
+	)
+
+	checkBuffer := func(expected []any) {
+		checkBuffer(c, client, expected)
+	}
+	addEntry := func(s string) {
+		err := client.Add(servicelog.Entry{Message: s})
+		c.Assert(err, IsNil)
+	}
+
+	checkBuffer([]any{nil, nil, nil, nil, nil, nil})
+	addEntry("1")
+	checkBuffer([]any{"1", nil, nil, nil, nil, nil})
+	addEntry("2")
+	checkBuffer([]any{"1", "2", nil, nil, nil, nil})
+	addEntry("3")
+	checkBuffer([]any{"1", "2", "3", nil, nil, nil})
+	addEntry("4")
+	checkBuffer([]any{nil, "2", "3", "4", nil, nil})
+	addEntry("5")
+	checkBuffer([]any{nil, nil, "3", "4", "5", nil})
+	addEntry("6")
+	checkBuffer([]any{nil, nil, nil, "4", "5", "6"})
+	addEntry("7")
+	checkBuffer([]any{"5", "6", "7", nil, nil, nil})
+}
+
+// Check if the client's buffer is as expected
+func checkBuffer(c *C, client *loki.Client, expected []any) {
+	buffer := loki.GetBuffer(client)
+	if len(buffer) != len(expected) {
+		c.Fatalf("buffer length is %v, expected %v", len(buffer), len(expected))
+	}
+
+	for i := range expected {
+		// 'nil' means c.buffer[i] should be zero
+		if expected[i] == nil {
+			c.Assert(buffer[i], DeepEquals, loki.LokiEntryWithService{},
+				Commentf("buffer[%d] should be zero, obtained %v", i, buffer[i]))
+
+		} else if msg, ok := expected[i].(string); ok {
+			// Check buffer message matches
+			c.Assert(loki.GetMessage(buffer[i]), Equals, msg)
+
+		} else {
+			c.Fatalf("invalid value expected[%d] = %v %T", i, expected[i], expected[i])
+		}
+	}
+}
+
 // Strips all extraneous whitespace from JSON
 func compactJSON(s string) []byte {
 	var buf bytes.Buffer