GODT-1077 IMAP sync counting

internal/imap/msg_build_counts.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2021 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge 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 ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imap
+
+import (
+	"fmt"
+	"sync"
+)
+
+// msgBuildCountHistogram is used to analyse and log the number of repetitive
+// downloads of requested messages per one fetch. The number of builds per each
+// messageID is stored in persistent database. The msgBuildCountHistogram will
+// take this number for each message in ongoing fetch and create histogram of
+// repeats.
+//
+// Example: During `fetch 1:300` there were
+// - 100 messages were downloaded first time
+// - 100 messages were downloaded second time
+// - 99 messages were downloaded 10th times
+// - 1 messages were downloaded 100th times
+type msgBuildCountHistogram struct {
+	// Key represents how many times message was build.
+	// Value stores how many messages are build X times based on the key.
+	counts map[uint32]uint32
+	lock   sync.Locker
+}
+
+func newMsgBuildCountHistogram() *msgBuildCountHistogram {
+	return &msgBuildCountHistogram{
+		counts: map[uint32]uint32{},
+		lock:   &sync.Mutex{},
+	}
+}
+
+func (c *msgBuildCountHistogram) String() string {
+	res := ""
+	for nRebuild, counts := range c.counts {
+		if res != "" {
+			res += ", "
+		}
+		res += fmt.Sprintf("[%d]:%d", nRebuild, counts)
+	}
+	return res
+}
+
+func (c *msgBuildCountHistogram) add(nRebuild uint32) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.counts[nRebuild]++
+}