From a63fe958aeae690dba4754cd9ecedd449f2770b9 Mon Sep 17 00:00:00 2001
From: Eugene Bujak <hmage@hmage.net>
Date: Sun, 7 Oct 2018 02:17:22 +0300
Subject: [PATCH] Querylog -- Read from querylog files when answering to
/querylog API, it now survives restarts.
---
coredns_plugin/querylog.go | 5 ++
coredns_plugin/querylog_file.go | 87 +++++++++++++++++++++++++++++++++
2 files changed, 92 insertions(+)
diff --git a/coredns_plugin/querylog.go b/coredns_plugin/querylog.go
index eb848fb8..381ac16a 100644
--- a/coredns_plugin/querylog.go
+++ b/coredns_plugin/querylog.go
@@ -88,6 +88,11 @@ func handleQueryLog(w http.ResponseWriter, r *http.Request) {
logBufferLock.RLock()
values := logBuffer
logBufferLock.RUnlock()
+
+ if len(values) < queryLogAPI {
+ values = appendFromLogFile(values, queryLogAPI, time.Hour*24)
+ }
+
var data = []map[string]interface{}{}
for _, entry := range values {
var q *dns.Msg
diff --git a/coredns_plugin/querylog_file.go b/coredns_plugin/querylog_file.go
index 1cfa93a7..412817ed 100644
--- a/coredns_plugin/querylog_file.go
+++ b/coredns_plugin/querylog_file.go
@@ -144,3 +144,90 @@ func periodicQueryLogRotate(t time.Duration) {
}
}
}
+
+func appendFromLogFile(values []logEntry, maxLen int, timeWindow time.Duration) []logEntry {
+ now := time.Now()
+ // read from querylog files, try newest file first
+ files := []string{
+ queryLogFileName + ".gz",
+ queryLogFileName + ".gz.1",
+ }
+
+ a := []logEntry{}
+
+ // read from all files
+ for _, file := range files {
+ if len(a) >= maxLen {
+ // previous file filled us with enough fresh entries
+ break
+ }
+ if _, err := os.Stat(file); os.IsNotExist(err) {
+ // do nothing, file doesn't exist
+ continue
+ }
+
+ trace("Opening file %s", file)
+ f, err := os.Open(file)
+ if err != nil {
+ log.Printf("Failed to open file \"%s\": %s", file, err)
+ // try next file
+ continue
+ }
+ defer f.Close()
+
+ trace("Creating gzip reader")
+ zr, err := gzip.NewReader(f)
+ if err != nil {
+ log.Printf("Failed to create gzip reader: %s", err)
+ continue
+ }
+
+ trace("Creating json decoder")
+ d := json.NewDecoder(zr)
+
+ i := 0
+ // entries on file are in oldest->newest order
+ // we want maxLen newest
+ for d.More() {
+ var entry logEntry
+ err := d.Decode(&entry)
+ if err != nil {
+ log.Printf("Failed to decode: %s", err)
+ // next entry can be fine, try more
+ continue
+ }
+
+ if now.Sub(entry.Time) > timeWindow {
+ trace("skipping entry")
+ continue
+ }
+
+ i++
+ a = append(a, entry)
+ if len(a) > maxLen {
+ toskip := len(a) - maxLen
+ a = a[toskip:]
+ }
+ }
+ err = zr.Close()
+ if err != nil {
+ log.Printf("Encountered error while closing gzip reader: %s", err)
+ }
+ log.Printf("file \"%s\": read %d entries", file, i)
+ }
+
+ // now that we've read all eligible entries, reverse the slice to make it go from newest->oldest
+ for left, right := 0, len(a)-1; left < right; left, right = left+1, right-1 {
+ a[left], a[right] = a[right], a[left]
+ }
+
+ // append it to values
+ values = append(values, a...)
+
+ // then cut off of it is bigger than maxLen
+ if len(values) > maxLen {
+ values = values[:maxLen]
+ }
+
+ return values
+}