+ statistics: store in separate file

+ GET /control/stats handler

AGHTechDoc.md

@@ -37,6 +37,11 @@ Contents:
 * Services Filter
 	* API: Get blocked services list
 	* API: Set blocked services list
+* Statistics
+	* API: Get statistics data
+	* API: Clear statistics data
+	* API: Set statistics parameters
+	* API: Get statistics parameters
 
 
 ## First startup
@@ -863,3 +868,111 @@ Request:
 Response:
 
 	200 OK
+
+
+## Statistics
+
+Load (main thread):
+. Load data from the last bucket from DB for the current hour
+
+Runtime (DNS worker threads):
+. Update current unit
+
+Runtime (goroutine):
+. Periodically check that current unit should be flushed to file (when the current hour changes)
+ . If so, flush it, allocate a new empty unit
+
+Runtime (HTTP worker threads):
+. To respond to "Get statistics" API request we:
+ . load all units from file
+ . load current unit
+ . process data from all loaded units:
+  . sum up data for "total counters" output values
+  . add value into "per time unit counters" output arrays
+  . aggregate data for "top_" output arrays;  sort in descending order
+
+Unload (main thread):
+. Flush current unit to file
+
+
+### API: Get statistics data
+
+Request:
+
+	GET /control/stats
+
+Response:
+
+	200 OK
+
+	{
+		time_units: hours | days
+
+		// total counters:
+		num_dns_queries: 123
+		num_blocked_filtering: 123
+		num_replaced_safebrowsing: 123
+		num_replaced_safesearch: 123
+		num_replaced_parental: 123
+		avg_processing_time: 123.123
+
+		// per time unit counters
+		dns_queries: [123, ...]
+		blocked_filtering: [123, ...]
+		replaced_parental: [123, ...]
+		replaced_safebrowsing: [123, ...]
+
+		top_queried_domains: [
+			{host: 123},
+			...
+		]
+		top_blocked_domains: [
+			{host: 123},
+			...
+		]
+		top_clients: [
+			{IP: 123},
+			...
+		]
+	}
+
+
+### API: Clear statistics data
+
+Request:
+
+	POST /control/stats_reset
+
+Response:
+
+	200 OK
+
+
+### API: Set statistics parameters
+
+Request:
+
+	POST /control/stats_config
+
+	{
+		"interval": 1 | 7 | 30 | 90
+	}
+
+Response:
+
+	200 OK
+
+
+### API: Get statistics parameters
+
+Request:
+
+	GET /control/stats_info
+
+Response:
+
+	200 OK
+
+	{
+		"interval": 1 | 7 | 30 | 90
+	}

dnsforward/dnsforward.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/dnsfilter"
+	"github.com/AdguardTeam/AdGuardHome/stats"
 	"github.com/AdguardTeam/dnsproxy/proxy"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/log"
@@ -40,6 +41,7 @@ type Server struct {
 	dnsProxy  *proxy.Proxy         // DNS proxy instance
 	dnsFilter *dnsfilter.Dnsfilter // DNS filter instance
 	queryLog  *queryLog            // Query log instance
+	stats     stats.Stats
 
 	AllowedClients         map[string]bool // IP addresses of whitelist clients
 	DisallowedClients      map[string]bool // IP addresses of clients that should be blocked
@@ -54,10 +56,11 @@ type Server struct {
 // NewServer creates a new instance of the dnsforward.Server
 // baseDir is the base directory for query logs
 // Note: this function must be called only once
-func NewServer(baseDir string) *Server {
+func NewServer(baseDir string, stats stats.Stats) *Server {
 	s := &Server{
 		queryLog: newQueryLog(baseDir),
 	}
+	s.stats = stats
 
 	log.Printf("Start DNS server periodic jobs")
 	go s.queryLog.periodicQueryLogRotate()
@@ -465,8 +468,8 @@ func (s *Server) handleDNSRequest(p *proxy.Proxy, d *proxy.DNSContext) error {
 		shouldLog = false
 	}
 
+	elapsed := time.Since(start)
 	if s.conf.QueryLogEnabled && shouldLog {
-		elapsed := time.Since(start)
 		upstreamAddr := ""
 		if d.Upstream != nil {
 			upstreamAddr = d.Upstream.Address()
@@ -474,9 +477,52 @@ func (s *Server) handleDNSRequest(p *proxy.Proxy, d *proxy.DNSContext) error {
 		_ = s.queryLog.logRequest(msg, d.Res, res, elapsed, d.Addr, upstreamAddr)
 	}
 
+	s.updateStats(d, elapsed, *res)
+
 	return nil
 }
 
+func (s *Server) updateStats(d *proxy.DNSContext, elapsed time.Duration, res dnsfilter.Result) {
+	if s.stats == nil {
+		return
+	}
+
+	e := stats.Entry{}
+	e.Domain = strings.ToLower(d.Req.Question[0].Name)
+	e.Domain = e.Domain[:len(e.Domain)-1] // remove last "."
+	switch addr := d.Addr.(type) {
+	case *net.UDPAddr:
+		e.Client = addr.IP
+	case *net.TCPAddr:
+		e.Client = addr.IP
+	}
+	e.Time = uint(elapsed / 1000)
+	switch res.Reason {
+
+	case dnsfilter.NotFilteredNotFound:
+		fallthrough
+	case dnsfilter.NotFilteredWhiteList:
+		fallthrough
+	case dnsfilter.NotFilteredError:
+		e.Result = stats.RNotFiltered
+
+	case dnsfilter.FilteredSafeBrowsing:
+		e.Result = stats.RSafeBrowsing
+	case dnsfilter.FilteredParental:
+		e.Result = stats.RParental
+	case dnsfilter.FilteredSafeSearch:
+		e.Result = stats.RSafeSearch
+
+	case dnsfilter.FilteredBlackList:
+		fallthrough
+	case dnsfilter.FilteredInvalid:
+		fallthrough
+	case dnsfilter.FilteredBlockedService:
+		e.Result = stats.RFiltered
+	}
+	s.stats.Update(e)
+}
+
 // filterDNSRequest applies the dnsFilter and sets d.Res if the request was filtered
 func (s *Server) filterDNSRequest(d *proxy.DNSContext) (*dnsfilter.Result, error) {
 	var res dnsfilter.Result

dnsforward/dnsforward_test.go

@@ -422,7 +422,7 @@ func TestBlockedBySafeBrowsing(t *testing.T) {
 }
 
 func createTestServer(t *testing.T) *Server {
-	s := NewServer(createDataDir(t))
+	s := NewServer(createDataDir(t), nil)
 	s.conf.UDPListenAddr = &net.UDPAddr{Port: 0}
 	s.conf.TCPListenAddr = &net.TCPAddr{Port: 0}
 

go.mod

@@ -7,7 +7,9 @@ require (
 	github.com/AdguardTeam/golibs v0.2.1
 	github.com/AdguardTeam/urlfilter v0.5.0
 	github.com/NYTimes/gziphandler v1.1.1
+	github.com/asaskevich/govalidator v0.0.0-20180720115003-f9ffefc3facf
 	github.com/bluele/gcache v0.0.0-20190518031135-bc40bd653833
+	github.com/etcd-io/bbolt v1.3.3
 	github.com/go-test/deep v1.0.1
 	github.com/gobuffalo/packr v1.19.0
 	github.com/joomcode/errorx v0.8.0
@@ -17,8 +19,8 @@ require (
 	github.com/miekg/dns v1.1.8
 	github.com/sparrc/go-ping v0.0.0-20181106165434-ef3ab45e41b0
 	github.com/stretchr/testify v1.4.0
+	go.etcd.io/bbolt v1.3.3 // indirect
 	golang.org/x/net v0.0.0-20190620200207-3b0461eec859
 	golang.org/x/sys v0.0.0-20190624142023-c5567b49c5d0
-	gopkg.in/asaskevich/govalidator.v4 v4.0.0-20160518190739-766470278477
 	gopkg.in/yaml.v2 v2.2.2
 )

go.sum

@@ -28,6 +28,7 @@ github.com/bluele/gcache v0.0.0-20190518031135-bc40bd653833/go.mod h1:8c4/i2Vlov
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/etcd-io/bbolt v1.3.3/go.mod h1:ZF2nL25h33cCyBtcyWeZ2/I3HQOfTP+0PIEvHjkjCrw=
 github.com/go-ole/go-ole v1.2.4 h1:nNBDSCOigTSiarFpYE9J/KtEA1IOW4CNeqT9TQDqCxI=
 github.com/go-ole/go-ole v1.2.4/go.mod h1:XCwSNxSkXRo4vlyPy93sltvi/qJq0jqQhjqQNIwKuxM=
 github.com/go-test/deep v1.0.1 h1:UQhStjbkDClarlmv0am7OXXO4/GaPdCGiUiMTvi28sg=
@@ -80,6 +81,7 @@ github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9 h1:mKdxBk7AujPs8kU4m80U72y/zjbZ3UcXC7dClwKbUI0=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=
@@ -112,8 +114,6 @@ golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-gopkg.in/asaskevich/govalidator.v4 v4.0.0-20160518190739-766470278477 h1:5xUJw+lg4zao9W4HIDzlFbMYgSgtvNVHh00MEHvbGpQ=
-gopkg.in/asaskevich/govalidator.v4 v4.0.0-20160518190739-766470278477/go.mod h1:QDV1vrFSrowdoOba0UM8VJPUZONT7dnfdLsM+GG53Z8=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

home/config.go

@@ -12,6 +12,7 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/dhcpd"
 	"github.com/AdguardTeam/AdGuardHome/dnsfilter"
 	"github.com/AdguardTeam/AdGuardHome/dnsforward"
+	"github.com/AdguardTeam/AdGuardHome/stats"
 	"github.com/AdguardTeam/golibs/file"
 	"github.com/AdguardTeam/golibs/log"
 	yaml "gopkg.in/yaml.v2"
@@ -68,6 +69,7 @@ type configuration struct {
 	controlLock      sync.Mutex
 	transport        *http.Transport
 	client           *http.Client
+	stats            stats.Stats
 
 	// cached version.json to avoid hammering github.io for each page reload
 	versionCheckJSON     []byte

home/control_stats.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"net/http"
 
+	"github.com/AdguardTeam/AdGuardHome/stats"
 	"github.com/AdguardTeam/golibs/log"
 )
 
@@ -11,9 +12,8 @@ type statsConfig struct {
 	Interval uint `json:"interval"`
 }
 
+// Get stats configuration
 func handleStatsInfo(w http.ResponseWriter, r *http.Request) {
-	log.Tracef("%s %v", r.Method, r.URL)
-
 	resp := statsConfig{}
 	resp.Interval = config.DNS.StatsInterval
 
@@ -29,9 +29,8 @@ func handleStatsInfo(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// Set stats configuration
 func handleStatsConfig(w http.ResponseWriter, r *http.Request) {
-	log.Tracef("%s %v", r.Method, r.URL)
-
 	reqData := statsConfig{}
 	err := json.NewDecoder(r.Body).Decode(&reqData)
 	if err != nil {
@@ -45,8 +44,47 @@ func handleStatsConfig(w http.ResponseWriter, r *http.Request) {
 	}
 
 	config.DNS.StatsInterval = reqData.Interval
+	config.stats.Configure(int(config.DNS.StatsInterval))
 
-	httpUpdateConfigReloadDNSReturnOK(w, r)
+	returnOK(w)
+}
+
+// handleStats returns aggregated stats data
+func handleStats(w http.ResponseWriter, r *http.Request) {
+	units := stats.Hours
+	if config.DNS.StatsInterval > 7 {
+		units = stats.Days
+	}
+	counter := log.StartTimer()
+	d := config.stats.GetData(units)
+	counter.LogElapsed("Stats: prepared data")
+
+	if d == nil {
+		httpError(w, http.StatusInternalServerError, "Couldn't get statistics data")
+		return
+	}
+
+	data, err := json.Marshal(d)
+	if err != nil {
+		httpError(w, http.StatusInternalServerError, "json encode: %s", err)
+		return
+	}
+
+	w.Write(data)
+}
+
+// handleStatsReset resets the stats
+func handleStatsReset(w http.ResponseWriter, r *http.Request) {
+	config.stats.Clear()
+	returnOK(w)
+}
+
+// RegisterStatsHandlers - register handlers
+func RegisterStatsHandlers() {
+	httpRegister(http.MethodGet, "/control/stats", handleStats)
+	httpRegister(http.MethodPost, "/control/stats_reset", handleStatsReset)
+	httpRegister(http.MethodPost, "/control/stats_config", handleStatsConfig)
+	httpRegister(http.MethodGet, "/control/stats_info", handleStatsInfo)
 }
 
 func checkStatsInterval(i uint) bool {

home/dns.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/AdguardTeam/AdGuardHome/dnsfilter"
 	"github.com/AdguardTeam/AdGuardHome/dnsforward"
+	"github.com/AdguardTeam/AdGuardHome/stats"
 	"github.com/AdguardTeam/dnsproxy/proxy"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/log"
@@ -33,7 +34,11 @@ func initDNSServer(baseDir string) {
 		log.Fatalf("Cannot create DNS data dir at %s: %s", baseDir, err)
 	}
 
-	config.dnsServer = dnsforward.NewServer(baseDir)
+	config.stats = stats.New("./data/stats.db", int(config.DNS.StatsInterval), nil)
+	if config.stats == nil {
+		log.Fatal("config.stats == nil")
+	}
+	config.dnsServer = dnsforward.NewServer(baseDir, config.stats)
 
 	initRDNS()
 }
@@ -178,5 +183,7 @@ func stopDNSServer() error {
 		return errorx.Decorate(err, "Couldn't stop forwarding DNS server")
 	}
 
+	config.stats.Close()
+
 	return nil
 }

stats/stats.go

@@ -0,0 +1,68 @@
+// Module for managing statistics for DNS filtering server
+
+package stats
+
+import (
+	"net"
+)
+
+type unitIDCallback func() int
+
+// New - create object
+// filename: DB file name
+// limit: time limit (in days)
+// unitID: user function to get the current unit ID.  If nil, the current time hour is used.
+func New(filename string, limit int, unitID unitIDCallback) Stats {
+	return createObject(filename, limit, unitID)
+}
+
+// Stats - main interface
+type Stats interface {
+	// Close object.
+	// This function is not thread safe
+	//  (can't be called in parallel with any other function of this interface).
+	Close()
+
+	// Set new configuration at runtime.
+	// limit: time limit (in days)
+	Configure(limit int)
+
+	// Reset counters and clear database
+	Clear()
+
+	// Update counters
+	Update(e Entry)
+
+	// Get data
+	GetData(timeUnit TimeUnit) map[string]interface{}
+}
+
+// TimeUnit - time unit
+type TimeUnit int
+
+// Supported time units
+const (
+	Hours TimeUnit = iota
+	Days
+)
+
+// Result of DNS request processing
+type Result int
+
+// Supported result values
+const (
+	RNotFiltered Result = iota + 1
+	RFiltered
+	RSafeBrowsing
+	RSafeSearch
+	RParental
+	rLast
+)
+
+// Entry - data to add
+type Entry struct {
+	Domain string
+	Client net.IP
+	Result Result
+	Time   uint // processing time (msec)
+}

stats/stats_test.go

@@ -0,0 +1,115 @@
+package stats
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func UIntArrayEquals(a []uint, b []uint) bool {
+	if len(a) != len(b) {
+		return false
+	}
+
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+func TestStats(t *testing.T) {
+	s := New("./stats.db", 1, nil)
+
+	e := Entry{}
+
+	e.Domain = "domain"
+	e.Client = net.ParseIP("127.0.0.1")
+	e.Result = RFiltered
+	e.Time = 123456
+	s.Update(e)
+
+	e.Domain = "domain"
+	e.Client = net.ParseIP("127.0.0.1")
+	e.Result = RNotFiltered
+	e.Time = 123456
+	s.Update(e)
+
+	d := s.GetData(Hours)
+	a := []uint{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2}
+	assert.True(t, UIntArrayEquals(d["dns_queries"].([]uint), a))
+
+	a = []uint{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
+	assert.True(t, UIntArrayEquals(d["blocked_filtering"].([]uint), a))
+
+	a = []uint{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	assert.True(t, UIntArrayEquals(d["replaced_safebrowsing"].([]uint), a))
+
+	a = []uint{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	assert.True(t, UIntArrayEquals(d["replaced_parental"].([]uint), a))
+
+	m := d["top_queried_domains"].([]map[string]uint)
+	assert.True(t, m[0]["domain"] == 1)
+
+	m = d["top_blocked_domains"].([]map[string]uint)
+	assert.True(t, m[0]["domain"] == 1)
+
+	m = d["top_clients"].([]map[string]uint)
+	assert.True(t, m[0]["127.0.0.1"] == 2)
+
+	assert.True(t, d["num_dns_queries"].(uint) == 2)
+	assert.True(t, d["num_blocked_filtering"].(uint) == 1)
+	assert.True(t, d["num_replaced_safebrowsing"].(uint) == 0)
+	assert.True(t, d["num_replaced_safesearch"].(uint) == 0)
+	assert.True(t, d["num_replaced_parental"].(uint) == 0)
+	assert.True(t, d["avg_processing_time"].(float64) == 0.123456)
+
+	s.Clear()
+	s.Close()
+	os.Remove("./stats.db")
+}
+
+func TestLargeNumbers(t *testing.T) {
+	var hour int32
+	hour = 1
+	newID := func() int {
+		// use "atomic" to make Go race detector happy
+		return int(atomic.LoadInt32(&hour))
+	}
+
+	// log.SetLevel(log.DEBUG)
+	fn := "./stats.db"
+	os.Remove(fn)
+	s := New(fn, 1, newID)
+	e := Entry{}
+
+	n := 1000 // number of distinct clients and domains every hour
+	for h := 0; h != 12; h++ {
+		if h != 0 {
+			atomic.AddInt32(&hour, 1)
+			time.Sleep(1500 * time.Millisecond)
+		}
+		for i := 0; i != n; i++ {
+			e.Domain = fmt.Sprintf("domain%d", i)
+			e.Client = net.ParseIP("127.0.0.1")
+			e.Client[2] = byte((i & 0xff00) >> 8)
+			e.Client[3] = byte(i & 0xff)
+			e.Result = RNotFiltered
+			e.Time = 123456
+			s.Update(e)
+		}
+	}
+
+	d := s.GetData(Hours)
+	assert.True(t, d["num_dns_queries"].(uint) == uint(int(hour)*n))
+
+	s.Close()
+	os.Remove(fn)
+}

stats/stats_unit.go

@@ -0,0 +1,672 @@
+package stats
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/gob"
+	"fmt"
+	"os"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/AdguardTeam/golibs/log"
+	bolt "github.com/etcd-io/bbolt"
+)
+
+const (
+	maxDomains = 100 // max number of top domains to store in file or return via Get()
+	maxClients = 100 // max number of top clients to store in file or return via Get()
+)
+
+// statsCtx - global context
+type statsCtx struct {
+	limit    int            // maximum time we need to keep data for (in hours)
+	filename string         // database file name
+	unitID   unitIDCallback // user function which returns the current unit ID
+	db       *bolt.DB
+
+	unit     *unit      // the current unit
+	unitLock sync.Mutex // protect 'unit'
+}
+
+// data for 1 time unit
+type unit struct {
+	id int // unit ID.  Default: absolute hour since Jan 1, 1970
+
+	nTotal  int   // total requests
+	nResult []int // number of requests per one result
+	timeSum int   // sum of processing time of all requests (usec)
+
+	// top:
+	domains        map[string]int // number of requests per domain
+	blockedDomains map[string]int // number of blocked requests per domain
+	clients        map[string]int // number of requests per client
+}
+
+// name-count pair
+type countPair struct {
+	Name  string
+	Count uint
+}
+
+// structure for storing data in file
+type unitDB struct {
+	NTotal  uint
+	NResult []uint
+
+	Domains        []countPair
+	BlockedDomains []countPair
+	Clients        []countPair
+
+	TimeAvg uint // usec
+}
+
+func createObject(filename string, limitDays int, unitID unitIDCallback) *statsCtx {
+	s := statsCtx{}
+	s.limit = limitDays * 24
+	s.filename = filename
+	s.unitID = newUnitID
+	if unitID != nil {
+		s.unitID = unitID
+	}
+
+	if !s.dbOpen() {
+		return nil
+	}
+
+	id := s.unitID()
+	tx := s.beginTxn(true)
+	var udb *unitDB
+	if tx != nil {
+		log.Tracef("Deleting old units...")
+		firstID := id - s.limit - 1
+		unitDel := 0
+		forEachBkt := func(name []byte, b *bolt.Bucket) error {
+			id := btoi(name)
+			if id < firstID {
+				err := tx.DeleteBucket(name)
+				if err != nil {
+					log.Debug("tx.DeleteBucket: %s", err)
+				}
+				log.Debug("Stats: deleted unit %d", id)
+				unitDel++
+				return nil
+			}
+			return fmt.Errorf("")
+		}
+		_ = tx.ForEach(forEachBkt)
+
+		udb = s.loadUnitFromDB(tx, id)
+
+		if unitDel != 0 {
+			s.commitTxn(tx)
+		} else {
+			_ = tx.Rollback()
+		}
+	}
+
+	u := unit{}
+	s.initUnit(&u, id)
+	if udb != nil {
+		deserialize(&u, udb)
+	}
+	s.unit = &u
+
+	go s.periodicFlush()
+
+	log.Debug("Stats: initialized")
+	return &s
+}
+
+func (s *statsCtx) dbOpen() bool {
+	var err error
+	log.Tracef("db.Open...")
+	s.db, err = bolt.Open(s.filename, 0644, nil)
+	if err != nil {
+		log.Error("Stats: open DB: %s: %s", s.filename, err)
+		return false
+	}
+	log.Tracef("db.Open")
+	return true
+}
+
+// Atomically swap the currently active unit with a new value
+// Return old value
+func (s *statsCtx) swapUnit(new *unit) *unit {
+	s.unitLock.Lock()
+	u := s.unit
+	s.unit = new
+	s.unitLock.Unlock()
+	return u
+}
+
+// Get unit ID for the current hour
+func newUnitID() int {
+	return int(time.Now().Unix() / (60 * 60))
+}
+
+// Initialize a unit
+func (s *statsCtx) initUnit(u *unit, id int) {
+	u.id = id
+	u.nResult = make([]int, rLast)
+	u.domains = make(map[string]int)
+	u.blockedDomains = make(map[string]int)
+	u.clients = make(map[string]int)
+}
+
+// Open a DB transaction
+func (s *statsCtx) beginTxn(wr bool) *bolt.Tx {
+	db := s.db
+	if db == nil {
+		return nil
+	}
+
+	log.Tracef("db.Begin...")
+	tx, err := db.Begin(wr)
+	if err != nil {
+		log.Error("db.Begin: %s", err)
+		return nil
+	}
+	log.Tracef("db.Begin")
+	return tx
+}
+
+func (s *statsCtx) commitTxn(tx *bolt.Tx) {
+	err := tx.Commit()
+	if err != nil {
+		log.Debug("tx.Commit: %s", err)
+		return
+	}
+	log.Tracef("tx.Commit")
+}
+
+// Get unit name
+func unitName(id int) []byte {
+	return itob(id)
+}
+
+// Convert integer to 8-byte array (big endian)
+func itob(v int) []byte {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, uint64(v))
+	return b
+}
+
+// Convert 8-byte array (big endian) to integer
+func btoi(b []byte) int {
+	return int(binary.BigEndian.Uint64(b))
+}
+
+// Flush the current unit to DB and delete an old unit when a new hour is started
+func (s *statsCtx) periodicFlush() {
+	for {
+		s.unitLock.Lock()
+		ptr := s.unit
+		s.unitLock.Unlock()
+		if ptr == nil {
+			break
+		}
+
+		id := s.unitID()
+		if ptr.id == id {
+			time.Sleep(time.Second)
+			continue
+		}
+
+		nu := unit{}
+		s.initUnit(&nu, id)
+		u := s.swapUnit(&nu)
+		udb := serialize(u)
+
+		tx := s.beginTxn(true)
+		if tx == nil {
+			continue
+		}
+		ok1 := s.flushUnitToDB(tx, u.id, udb)
+		ok2 := s.deleteUnit(tx, id-s.limit)
+		if ok1 || ok2 {
+			s.commitTxn(tx)
+		} else {
+			_ = tx.Rollback()
+		}
+	}
+	log.Tracef("periodicFlush() exited")
+}
+
+// Delete unit's data from file
+func (s *statsCtx) deleteUnit(tx *bolt.Tx, id int) bool {
+	err := tx.DeleteBucket(unitName(id))
+	if err != nil {
+		log.Tracef("bolt DeleteBucket: %s", err)
+		return false
+	}
+	log.Debug("Stats: deleted unit %d", id)
+	return true
+}
+
+func convertMapToArray(m map[string]int, max int) []countPair {
+	a := []countPair{}
+	for k, v := range m {
+		pair := countPair{}
+		pair.Name = k
+		pair.Count = uint(v)
+		a = append(a, pair)
+	}
+	less := func(i, j int) bool {
+		if a[i].Count >= a[j].Count {
+			return true
+		}
+		return false
+	}
+	sort.Slice(a, less)
+	if max > len(a) {
+		max = len(a)
+	}
+	return a[:max]
+}
+
+func convertArrayToMap(a []countPair) map[string]int {
+	m := map[string]int{}
+	for _, it := range a {
+		m[it.Name] = int(it.Count)
+	}
+	return m
+}
+
+func serialize(u *unit) *unitDB {
+	udb := unitDB{}
+	udb.NTotal = uint(u.nTotal)
+	for _, it := range u.nResult {
+		udb.NResult = append(udb.NResult, uint(it))
+	}
+	if u.nTotal != 0 {
+		udb.TimeAvg = uint(u.timeSum / u.nTotal)
+	}
+	udb.Domains = convertMapToArray(u.domains, maxDomains)
+	udb.BlockedDomains = convertMapToArray(u.blockedDomains, maxDomains)
+	udb.Clients = convertMapToArray(u.clients, maxClients)
+	return &udb
+}
+
+func deserialize(u *unit, udb *unitDB) {
+	u.nTotal = int(udb.NTotal)
+	for _, it := range udb.NResult {
+		u.nResult = append(u.nResult, int(it))
+	}
+	u.domains = convertArrayToMap(udb.Domains)
+	u.blockedDomains = convertArrayToMap(udb.BlockedDomains)
+	u.clients = convertArrayToMap(udb.Clients)
+	u.timeSum = int(udb.TimeAvg) * u.nTotal
+}
+
+func (s *statsCtx) flushUnitToDB(tx *bolt.Tx, id int, udb *unitDB) bool {
+	log.Tracef("Flushing unit %d", id)
+
+	bkt, err := tx.CreateBucketIfNotExists(unitName(id))
+	if err != nil {
+		log.Error("tx.CreateBucketIfNotExists: %s", err)
+		return false
+	}
+
+	var buf bytes.Buffer
+	enc := gob.NewEncoder(&buf)
+	err = enc.Encode(udb)
+	if err != nil {
+		log.Error("gob.Encode: %s", err)
+		return false
+	}
+
+	err = bkt.Put([]byte{0}, buf.Bytes())
+	if err != nil {
+		log.Error("bkt.Put: %s", err)
+		return false
+	}
+
+	return true
+}
+
+func (s *statsCtx) loadUnitFromDB(tx *bolt.Tx, id int) *unitDB {
+	bkt := tx.Bucket(unitName(id))
+	if bkt == nil {
+		return nil
+	}
+
+	log.Tracef("Loading unit %d", id)
+
+	var buf bytes.Buffer
+	buf.Write(bkt.Get([]byte{0}))
+	dec := gob.NewDecoder(&buf)
+	udb := unitDB{}
+	err := dec.Decode(&udb)
+	if err != nil {
+		log.Error("gob Decode: %s", err)
+		return nil
+	}
+
+	return &udb
+}
+
+func convertTopArray(a []countPair) []map[string]uint {
+	m := []map[string]uint{}
+	for _, it := range a {
+		ent := map[string]uint{}
+		ent[it.Name] = it.Count
+		m = append(m, ent)
+	}
+	return m
+}
+
+func (s *statsCtx) Configure(limit int) {
+	if limit < 0 {
+		return
+	}
+	s.limit = limit * 24
+	log.Debug("Stats: set limit: %d", limit)
+}
+
+func (s *statsCtx) Close() {
+	u := s.swapUnit(nil)
+	udb := serialize(u)
+	tx := s.beginTxn(true)
+	if tx != nil {
+		if s.flushUnitToDB(tx, u.id, udb) {
+			s.commitTxn(tx)
+		} else {
+			_ = tx.Rollback()
+		}
+	}
+
+	if s.db != nil {
+		log.Tracef("db.Close...")
+		_ = s.db.Close()
+		log.Tracef("db.Close")
+	}
+
+	log.Debug("Stats: closed")
+}
+
+func (s *statsCtx) Clear() {
+	tx := s.beginTxn(true)
+	if tx != nil {
+		db := s.db
+		s.db = nil
+		_ = tx.Rollback()
+		// the active transactions can continue using database,
+		//  but no new transactions will be opened
+		_ = db.Close()
+		log.Tracef("db.Close")
+		// all active transactions are now closed
+	}
+
+	u := unit{}
+	s.initUnit(&u, s.unitID())
+	_ = s.swapUnit(&u)
+
+	err := os.Remove(s.filename)
+	if err != nil {
+		log.Error("os.Remove: %s", err)
+	}
+
+	_ = s.dbOpen()
+
+	log.Debug("Stats: cleared")
+}
+
+func (s *statsCtx) Update(e Entry) {
+	if e.Result == 0 ||
+		len(e.Domain) == 0 ||
+		!(len(e.Client) == 4 || len(e.Client) == 16) {
+		return
+	}
+	client := e.Client.String()
+
+	s.unitLock.Lock()
+	u := s.unit
+
+	u.nResult[e.Result]++
+
+	if e.Result == RNotFiltered {
+		u.domains[e.Domain]++
+	} else {
+		u.blockedDomains[e.Domain]++
+	}
+
+	u.clients[client]++
+	u.timeSum += int(e.Time)
+	u.nTotal++
+	s.unitLock.Unlock()
+}
+
+/* Algorithm:
+. Prepare array of N units, where N is the value of "limit" configuration setting
+ . Load data for the most recent units from file
+   If a unit with required ID doesn't exist, just add an empty unit
+ . Get data for the current unit
+. Process data from the units and prepare an output map object:
+ * per time unit counters:
+  * DNS-queries/time-unit
+  * blocked/time-unit
+  * safebrowsing-blocked/time-unit
+  * parental-blocked/time-unit
+  If time-unit is an hour, just add values from each unit to an array.
+  If time-unit is a day, aggregate per-hour data into days.
+ * top counters:
+  * queries/domain
+  * queries/blocked-domain
+  * queries/client
+  To get these values we first sum up data for all units into a single map.
+  Then we get the pairs with the highest numbers (the values are sorted in descending order)
+ * total counters:
+  * DNS-queries
+  * blocked
+  * safebrowsing-blocked
+  * safesearch-blocked
+  * parental-blocked
+  These values are just the sum of data for all units.
+*/
+// nolint (gocyclo)
+func (s *statsCtx) GetData(timeUnit TimeUnit) map[string]interface{} {
+	d := map[string]interface{}{}
+
+	tx := s.beginTxn(false)
+	if tx == nil {
+		return nil
+	}
+
+	units := []*unitDB{} //per-hour units
+	lastID := s.unitID()
+	firstID := lastID - s.limit + 1
+	for i := firstID; i != lastID; i++ {
+		u := s.loadUnitFromDB(tx, i)
+		if u == nil {
+			u = &unitDB{}
+			u.NResult = make([]uint, rLast)
+		}
+		units = append(units, u)
+	}
+
+	_ = tx.Rollback()
+
+	s.unitLock.Lock()
+	cu := serialize(s.unit)
+	cuID := s.unit.id
+	s.unitLock.Unlock()
+	if cuID != lastID {
+		units = units[1:]
+	}
+	units = append(units, cu)
+
+	if len(units) != s.limit {
+		log.Fatalf("len(units) != s.limit: %d %d", len(units), s.limit)
+	}
+
+	// per time unit counters:
+
+	// 720 hours may span 31 days, so we skip data for the first day in this case
+	firstDayID := (firstID + 24 - 1) / 24 * 24 // align_ceil(24)
+
+	a := []uint{}
+	if timeUnit == Hours {
+		for _, u := range units {
+			a = append(a, u.NTotal)
+		}
+	} else {
+		var sum uint
+		id := firstDayID
+		nextDayID := firstDayID + 24
+		for i := firstDayID - firstID; i != len(units); i++ {
+			sum += units[i].NTotal
+			if id == nextDayID {
+				a = append(a, sum)
+				sum = 0
+				nextDayID += 24
+			}
+			id++
+		}
+		if id < nextDayID {
+			a = append(a, sum)
+		}
+		if len(a) != s.limit/24 {
+			log.Fatalf("len(a) != s.limit: %d %d", len(a), s.limit)
+		}
+	}
+	d["dns_queries"] = a
+
+	a = []uint{}
+	if timeUnit == Hours {
+		for _, u := range units {
+			a = append(a, u.NResult[RFiltered])
+		}
+	} else {
+		var sum uint
+		id := firstDayID
+		nextDayID := firstDayID + 24
+		for i := firstDayID - firstID; i != len(units); i++ {
+			sum += units[i].NResult[RFiltered]
+			if id == nextDayID {
+				a = append(a, sum)
+				sum = 0
+				nextDayID += 24
+			}
+			id++
+		}
+		if id < nextDayID {
+			a = append(a, sum)
+		}
+	}
+	d["blocked_filtering"] = a
+
+	a = []uint{}
+	if timeUnit == Hours {
+		for _, u := range units {
+			a = append(a, u.NResult[RSafeBrowsing])
+		}
+	} else {
+		var sum uint
+		id := firstDayID
+		nextDayID := firstDayID + 24
+		for i := firstDayID - firstID; i != len(units); i++ {
+			sum += units[i].NResult[RSafeBrowsing]
+			if id == nextDayID {
+				a = append(a, sum)
+				sum = 0
+				nextDayID += 24
+			}
+			id++
+		}
+		if id < nextDayID {
+			a = append(a, sum)
+		}
+	}
+	d["replaced_safebrowsing"] = a
+
+	a = []uint{}
+	if timeUnit == Hours {
+		for _, u := range units {
+			a = append(a, u.NResult[RParental])
+		}
+	} else {
+		var sum uint
+		id := firstDayID
+		nextDayID := firstDayID + 24
+		for i := firstDayID - firstID; i != len(units); i++ {
+			sum += units[i].NResult[RParental]
+			if id == nextDayID {
+				a = append(a, sum)
+				sum = 0
+				nextDayID += 24
+			}
+			id++
+		}
+		if id < nextDayID {
+			a = append(a, sum)
+		}
+	}
+	d["replaced_parental"] = a
+
+	// top counters:
+
+	m := map[string]int{}
+	for _, u := range units {
+		for _, it := range u.Domains {
+			m[it.Name] += int(it.Count)
+		}
+	}
+	a2 := convertMapToArray(m, maxDomains)
+	d["top_queried_domains"] = convertTopArray(a2)
+
+	m = map[string]int{}
+	for _, u := range units {
+		for _, it := range u.BlockedDomains {
+			m[it.Name] += int(it.Count)
+		}
+	}
+	a2 = convertMapToArray(m, maxDomains)
+	d["top_blocked_domains"] = convertTopArray(a2)
+
+	m = map[string]int{}
+	for _, u := range units {
+		for _, it := range u.Clients {
+			m[it.Name] += int(it.Count)
+		}
+	}
+	a2 = convertMapToArray(m, maxClients)
+	d["top_clients"] = convertTopArray(a2)
+
+	// total counters:
+
+	sum := unitDB{}
+	timeN := 0
+	sum.NResult = make([]uint, rLast)
+	for _, u := range units {
+		sum.NTotal += u.NTotal
+		sum.TimeAvg += u.TimeAvg
+		if u.TimeAvg != 0 {
+			timeN++
+		}
+		sum.NResult[RFiltered] += u.NResult[RFiltered]
+		sum.NResult[RSafeBrowsing] += u.NResult[RSafeBrowsing]
+		sum.NResult[RSafeSearch] += u.NResult[RSafeSearch]
+		sum.NResult[RParental] += u.NResult[RParental]
+	}
+
+	d["num_dns_queries"] = sum.NTotal
+	d["num_blocked_filtering"] = sum.NResult[RFiltered]
+	d["num_replaced_safebrowsing"] = sum.NResult[RSafeBrowsing]
+	d["num_replaced_safesearch"] = sum.NResult[RSafeSearch]
+	d["num_replaced_parental"] = sum.NResult[RParental]
+
+	avgTime := float64(0)
+	if timeN != 0 {
+		avgTime = float64(sum.TimeAvg/uint(timeN)) / 1000000
+	}
+	d["avg_processing_time"] = avgTime
+
+	d["time_units"] = "hours"
+	if timeUnit == Days {
+		d["time_units"] = "days"
+	}
+
+	return d
+}