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tailscale/log/sockstatlog/logger.go

190 lines
5.3 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package sockstatlog provides a logger for capturing and storing network socket stats.
package sockstatlog
import (
"context"
"crypto/sha256"
"encoding/json"
"io"
"net/http"
"os"
"path/filepath"
"time"
"tailscale.com/logpolicy"
"tailscale.com/logtail"
"tailscale.com/logtail/filch"
"tailscale.com/net/sockstats"
"tailscale.com/smallzstd"
"tailscale.com/types/logger"
"tailscale.com/types/logid"
"tailscale.com/util/mak"
)
// pollPeriod specifies how often to poll for socket stats.
const pollPeriod = time.Second / 10
// Logger logs statistics about network sockets.
type Logger struct {
ctx context.Context
cancelFn context.CancelFunc
ticker *time.Ticker
logf logger.Logf
logger *logtail.Logger
}
// deltaStat represents the bytes transferred during a time period.
// The first element is transmitted bytes, the second element is received bytes.
type deltaStat [2]uint64
// event represents the socket stats on a specific interface during a time period.
type event struct {
// Time is when the event started as a Unix timestamp in milliseconds.
Time int64 `json:"t"`
// Duration is the duration of this event in milliseconds.
Duration int64 `json:"d"`
// IsCellularInterface is set to 1 if the traffic was sent over a cellular interface.
IsCellularInterface int `json:"c,omitempty"`
// Stats records the stats for each Label during the time period.
Stats map[sockstats.Label]deltaStat `json:"s"`
}
// SockstatLogID reproducibly derives a new logid.PrivateID for sockstat logging from a node's public backend log ID.
// The returned PrivateID is the sha256 sum of logID + "sockstat".
// If a node's public log ID becomes known, it is trivial to spoof sockstat logs for that node.
// Given the this is just for debugging, we're not too concerned about that.
func SockstatLogID(logID logid.PublicID) logid.PrivateID {
return logid.PrivateID(sha256.Sum256([]byte(logID.String() + "sockstat")))
}
// NewLogger returns a new Logger that will store stats in logdir.
// On platforms that do not support sockstat logging, a nil Logger will be returned.
// The returned Logger must be shut down with Shutdown when it is no longer needed.
func NewLogger(logdir string, logf logger.Logf, logID logid.PublicID) (*Logger, error) {
if !sockstats.IsAvailable {
return nil, nil
}
if err := os.MkdirAll(logdir, 0755); err != nil && !os.IsExist(err) {
return nil, err
}
filchPrefix := filepath.Join(logdir, "sockstats")
filch, err := filch.New(filchPrefix, filch.Options{ReplaceStderr: false})
if err != nil {
return nil, err
}
ctx, cancel := context.WithCancel(context.Background())
logger := &Logger{
ctx: ctx,
cancelFn: cancel,
ticker: time.NewTicker(pollPeriod),
logf: logf,
}
logger.logger = logtail.NewLogger(logtail.Config{
BaseURL: logpolicy.LogURL(),
PrivateID: SockstatLogID(logID),
Collection: "sockstats.log.tailscale.io",
Buffer: filch,
NewZstdEncoder: func() logtail.Encoder {
w, err := smallzstd.NewEncoder(nil)
if err != nil {
panic(err)
}
return w
},
FlushDelayFn: func() time.Duration {
// set flush delay to 100 years so it never flushes automatically
return 100 * 365 * 24 * time.Hour
},
Stderr: io.Discard, // don't log to stderr
HTTPC: &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost)},
}, logf)
go logger.poll()
return logger, nil
}
// poll fetches the current socket stats at the configured time interval,
// calculates the delta since the last poll, and logs any non-zero values.
// This method does not return.
func (l *Logger) poll() {
// last is the last set of socket stats we saw.
var lastStats *sockstats.SockStats
var lastTime time.Time
enc := json.NewEncoder(l.logger)
for {
select {
case <-l.ctx.Done():
return
case t := <-l.ticker.C:
stats := sockstats.Get()
if lastStats != nil {
diffstats := delta(lastStats, stats)
if len(diffstats) > 0 {
e := event{
Time: lastTime.UnixMilli(),
Duration: t.Sub(lastTime).Milliseconds(),
Stats: diffstats,
}
if stats.CurrentInterfaceCellular {
e.IsCellularInterface = 1
}
if err := enc.Encode(e); err != nil {
l.logf("sockstatlog: error encoding log: %v", err)
}
}
}
lastTime = t
lastStats = stats
}
}
}
func (l *Logger) LogID() string {
if l.logger == nil {
return ""
}
return l.logger.PrivateID().Public().String()
}
// Flush sends pending logs to the log server and flushes them from the local buffer.
func (l *Logger) Flush() {
l.logger.StartFlush()
}
func (l *Logger) Shutdown() {
l.ticker.Stop()
l.logger.Shutdown(context.Background())
l.cancelFn()
}
// delta calculates the delta stats between two SockStats snapshots.
// b is assumed to have occurred after a.
// Zero values are omitted from the returned map, and an empty map is returned if no bytes were transferred.
func delta(a, b *sockstats.SockStats) (stats map[sockstats.Label]deltaStat) {
if a == nil || b == nil {
return nil
}
for label, bs := range b.Stats {
as := a.Stats[label]
if as.TxBytes == bs.TxBytes && as.RxBytes == bs.RxBytes {
// fast path for unchanged stats
continue
}
mak.Set(&stats, label, deltaStat{bs.TxBytes - as.TxBytes, bs.RxBytes - as.RxBytes})
}
return stats
}