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tailscale/logtail/logtail.go

615 lines
16 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package logtail sends logs to log.tailscale.io.
package logtail
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"strconv"
"sync/atomic"
"time"
"tailscale.com/logtail/backoff"
"tailscale.com/net/interfaces"
tslogger "tailscale.com/types/logger"
"tailscale.com/wgengine/monitor"
)
// DefaultHost is the default host name to upload logs to when
// Config.BaseURL isn't provided.
const DefaultHost = "log.tailscale.io"
const (
// CollectionNode is the name of a logtail Config.Collection
// for tailscaled (or equivalent: IPNExtension, Android app).
CollectionNode = "tailnode.log.tailscale.io"
)
type Encoder interface {
EncodeAll(src, dst []byte) []byte
Close() error
}
type Config struct {
Collection string // collection name, a domain name
PrivateID PrivateID // machine-specific private identifier
BaseURL string // if empty defaults to "https://log.tailscale.io"
HTTPC *http.Client // if empty defaults to http.DefaultClient
SkipClientTime bool // if true, client_time is not written to logs
LowMemory bool // if true, logtail minimizes memory use
TimeNow func() time.Time // if set, subsitutes uses of time.Now
Stderr io.Writer // if set, logs are sent here instead of os.Stderr
StderrLevel int // max verbosity level to write to stderr; 0 means the non-verbose messages only
Buffer Buffer // temp storage, if nil a MemoryBuffer
NewZstdEncoder func() Encoder // if set, used to compress logs for transmission
// MetricsDelta, if non-nil, is a func that returns an encoding
// delta in clientmetrics to upload alongside existing logs.
// It can return either an empty string (for nothing) or a string
// that's safe to embed in a JSON string literal without further escaping.
MetricsDelta func() string
// DrainLogs, if non-nil, disables automatic uploading of new logs,
// so that logs are only uploaded when a token is sent to DrainLogs.
DrainLogs <-chan struct{}
}
func NewLogger(cfg Config, logf tslogger.Logf) *Logger {
if cfg.BaseURL == "" {
cfg.BaseURL = "https://" + DefaultHost
}
if cfg.HTTPC == nil {
cfg.HTTPC = http.DefaultClient
}
if cfg.TimeNow == nil {
cfg.TimeNow = time.Now
}
if cfg.Stderr == nil {
cfg.Stderr = os.Stderr
}
if cfg.Buffer == nil {
pendingSize := 256
if cfg.LowMemory {
pendingSize = 64
}
cfg.Buffer = NewMemoryBuffer(pendingSize)
}
l := &Logger{
privateID: cfg.PrivateID,
stderr: cfg.Stderr,
stderrLevel: int64(cfg.StderrLevel),
httpc: cfg.HTTPC,
url: cfg.BaseURL + "/c/" + cfg.Collection + "/" + cfg.PrivateID.String(),
lowMem: cfg.LowMemory,
buffer: cfg.Buffer,
skipClientTime: cfg.SkipClientTime,
sent: make(chan struct{}, 1),
sentinel: make(chan int32, 16),
drainLogs: cfg.DrainLogs,
timeNow: cfg.TimeNow,
bo: backoff.NewBackoff("logtail", logf, 30*time.Second),
metricsDelta: cfg.MetricsDelta,
shutdownStart: make(chan struct{}),
shutdownDone: make(chan struct{}),
}
if cfg.NewZstdEncoder != nil {
l.zstdEncoder = cfg.NewZstdEncoder()
}
ctx, cancel := context.WithCancel(context.Background())
l.uploadCancel = cancel
go l.uploading(ctx)
l.Write([]byte("logtail started"))
return l
}
// Logger writes logs, splitting them as configured between local
// logging facilities and uploading to a log server.
type Logger struct {
stderr io.Writer
stderrLevel int64 // accessed atomically
httpc *http.Client
url string
lowMem bool
skipClientTime bool
linkMonitor *monitor.Mon
buffer Buffer
sent chan struct{} // signal to speed up drain
drainLogs <-chan struct{} // if non-nil, external signal to attempt a drain
sentinel chan int32
timeNow func() time.Time
bo *backoff.Backoff
zstdEncoder Encoder
uploadCancel func()
explainedRaw bool
metricsDelta func() string // or nil
privateID PrivateID
shutdownStart chan struct{} // closed when shutdown begins
shutdownDone chan struct{} // closed when shutdown complete
}
// SetVerbosityLevel controls the verbosity level that should be
// written to stderr. 0 is the default (not verbose). Levels 1 or higher
// are increasingly verbose.
func (l *Logger) SetVerbosityLevel(level int) {
atomic.StoreInt64(&l.stderrLevel, int64(level))
}
// SetLinkMonitor sets the optional the link monitor.
//
// It should not be changed concurrently with log writes and should
// only be set once.
func (l *Logger) SetLinkMonitor(lm *monitor.Mon) {
l.linkMonitor = lm
}
// PrivateID returns the logger's private log ID.
//
// It exists for internal use only.
func (l *Logger) PrivateID() PrivateID { return l.privateID }
// Shutdown gracefully shuts down the logger while completing any
// remaining uploads.
//
// It will block, continuing to try and upload unless the passed
// context object interrupts it by being done.
// If the shutdown is interrupted, an error is returned.
func (l *Logger) Shutdown(ctx context.Context) error {
done := make(chan struct{})
go func() {
select {
case <-ctx.Done():
l.uploadCancel()
<-l.shutdownDone
case <-l.shutdownDone:
}
close(done)
}()
close(l.shutdownStart)
io.WriteString(l, "logger closing down\n")
<-done
if l.zstdEncoder != nil {
return l.zstdEncoder.Close()
}
return nil
}
// Close shuts down this logger object, the background log uploader
// process, and any associated goroutines.
//
// Deprecated: use Shutdown
func (l *Logger) Close() {
l.Shutdown(context.Background())
}
// drainBlock is called by drainPending when there are no logs to drain.
//
// In typical operation, every call to the Write method unblocks and triggers
// a buffer.TryReadline, so logs are written with very low latency.
//
// If the caller provides a DrainLogs channel, then unblock-drain-on-Write
// is disabled, and it is up to the caller to trigger unblock the drain.
func (l *Logger) drainBlock() (shuttingDown bool) {
if l.drainLogs == nil {
select {
case <-l.shutdownStart:
return true
case <-l.sent:
}
} else {
select {
case <-l.shutdownStart:
return true
case <-l.drainLogs:
}
}
return false
}
// drainPending drains and encodes a batch of logs from the buffer for upload.
// It uses scratch as its initial buffer.
// If no logs are available, drainPending blocks until logs are available.
func (l *Logger) drainPending(scratch []byte) (res []byte) {
buf := bytes.NewBuffer(scratch[:0])
buf.WriteByte('[')
entries := 0
var batchDone bool
const maxLen = 256 << 10
for buf.Len() < maxLen && !batchDone {
b, err := l.buffer.TryReadLine()
if err == io.EOF {
break
} else if err != nil {
b = []byte(fmt.Sprintf("reading ringbuffer: %v", err))
batchDone = true
} else if b == nil {
if entries > 0 {
break
}
batchDone = l.drainBlock()
continue
}
if len(b) == 0 {
continue
}
if b[0] != '{' || !json.Valid(b) {
// This is probably a log added to stderr by filch
// outside of the logtail logger. Encode it.
// Do not add a client time, as it could have been
// been written a long time ago.
if !l.explainedRaw {
fmt.Fprintf(l.stderr, "RAW-STDERR: ***\n")
fmt.Fprintf(l.stderr, "RAW-STDERR: *** Lines prefixed with RAW-STDERR below bypassed logtail and probably come from a previous run of the program\n")
fmt.Fprintf(l.stderr, "RAW-STDERR: ***\n")
fmt.Fprintf(l.stderr, "RAW-STDERR:\n")
l.explainedRaw = true
}
fmt.Fprintf(l.stderr, "RAW-STDERR: %s", b)
b = l.encodeText(b, true, 0)
}
if entries > 0 {
buf.WriteByte(',')
}
buf.Write(b)
entries++
}
buf.WriteByte(']')
if buf.Len() <= len("[]") {
return nil
}
return buf.Bytes()
}
// This is the goroutine that repeatedly uploads logs in the background.
func (l *Logger) uploading(ctx context.Context) {
defer close(l.shutdownDone)
scratch := make([]byte, 4096) // reusable buffer to write into
for {
body := l.drainPending(scratch)
origlen := -1 // sentinel value: uncompressed
// Don't attempt to compress tiny bodies; not worth the CPU cycles.
if l.zstdEncoder != nil && len(body) > 256 {
zbody := l.zstdEncoder.EncodeAll(body, nil)
// Only send it compressed if the bandwidth savings are sufficient.
// Just the extra headers associated with enabling compression
// are 50 bytes by themselves.
if len(body)-len(zbody) > 64 {
origlen = len(body)
body = zbody
}
}
for len(body) > 0 {
select {
case <-ctx.Done():
return
default:
}
uploaded, err := l.upload(ctx, body, origlen)
if err != nil {
if !l.internetUp() {
fmt.Fprintf(l.stderr, "logtail: internet down; waiting\n")
l.awaitInternetUp(ctx)
continue
}
fmt.Fprintf(l.stderr, "logtail: upload: %v\n", err)
}
l.bo.BackOff(ctx, err)
if uploaded {
break
}
}
select {
case <-l.shutdownStart:
return
default:
}
}
}
func (l *Logger) internetUp() bool {
if l.linkMonitor == nil {
// No way to tell, so assume it is.
return true
}
return l.linkMonitor.InterfaceState().AnyInterfaceUp()
}
func (l *Logger) awaitInternetUp(ctx context.Context) {
upc := make(chan bool, 1)
defer l.linkMonitor.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
if st.AnyInterfaceUp() {
select {
case upc <- true:
default:
}
}
})()
if l.internetUp() {
return
}
select {
case <-upc:
fmt.Fprintf(l.stderr, "logtail: internet back up\n")
case <-ctx.Done():
}
}
// upload uploads body to the log server.
// origlen indicates the pre-compression body length.
// origlen of -1 indicates that the body is not compressed.
func (l *Logger) upload(ctx context.Context, body []byte, origlen int) (uploaded bool, err error) {
req, err := http.NewRequest("POST", l.url, bytes.NewReader(body))
if err != nil {
// I know of no conditions under which this could fail.
// Report it very loudly.
// TODO record logs to disk
panic("logtail: cannot build http request: " + err.Error())
}
if origlen != -1 {
req.Header.Add("Content-Encoding", "zstd")
req.Header.Add("Orig-Content-Length", strconv.Itoa(origlen))
}
req.Header["User-Agent"] = nil // not worth writing one; save some bytes
maxUploadTime := 45 * time.Second
ctx, cancel := context.WithTimeout(ctx, maxUploadTime)
defer cancel()
req = req.WithContext(ctx)
compressedNote := "not-compressed"
if origlen != -1 {
compressedNote = "compressed"
}
resp, err := l.httpc.Do(req)
if err != nil {
return false, fmt.Errorf("log upload of %d bytes %s failed: %v", len(body), compressedNote, err)
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
uploaded = resp.StatusCode == 400 // the server saved the logs anyway
b, _ := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
return uploaded, fmt.Errorf("log upload of %d bytes %s failed %d: %q", len(body), compressedNote, resp.StatusCode, b)
}
// Try to read to EOF, in case server's response is
// chunked. We want to reuse the TCP connection if it's
// HTTP/1. On success, we expect 0 bytes.
// TODO(bradfitz): can remove a few days after 2020-04-04 once
// server is fixed.
if resp.ContentLength == -1 {
resp.Body.Read(make([]byte, 1))
}
return true, nil
}
// Flush uploads all logs to the server.
// It blocks until complete or there is an unrecoverable error.
func (l *Logger) Flush() error {
return nil
}
func (l *Logger) send(jsonBlob []byte) (int, error) {
n, err := l.buffer.Write(jsonBlob)
if l.drainLogs == nil {
select {
case l.sent <- struct{}{}:
default:
}
}
return n, err
}
// TODO: instead of allocating, this should probably just append
// directly into the output log buffer.
func (l *Logger) encodeText(buf []byte, skipClientTime bool, level int) []byte {
now := l.timeNow()
// Factor in JSON encoding overhead to try to only do one alloc
// in the make below (so appends don't resize the buffer).
overhead := 13
if !skipClientTime {
overhead += 67
}
// TODO: do a pass over buf and count how many backslashes will be needed?
// For now just factor in a dozen.
overhead += 12
// Put a sanity cap on buf's size.
max := 16 << 10
if l.lowMem {
max = 255
}
var nTruncated int
if len(buf) > max {
nTruncated = len(buf) - max
// TODO: this can break a UTF-8 character
// mid-encoding. We don't tend to log
// non-ASCII stuff ourselves, but e.g. client
// names might be.
buf = buf[:max]
}
b := make([]byte, 0, len(buf)+overhead)
b = append(b, '{')
if !skipClientTime {
b = append(b, `"logtail": {"client_time": "`...)
b = now.AppendFormat(b, time.RFC3339Nano)
b = append(b, "\"}, "...)
}
if l.metricsDelta != nil {
if d := l.metricsDelta(); d != "" {
b = append(b, `"metrics": "`...)
b = append(b, d...)
b = append(b, `",`...)
}
}
// Add the log level, if non-zero. Note that we only use log
// levels 1 and 2 currently. It's unlikely we'll ever make it
// past 9.
if level > 0 && level < 10 {
b = append(b, `"v":`...)
b = append(b, '0'+byte(level))
b = append(b, ',')
}
b = append(b, "\"text\": \""...)
for _, c := range buf {
switch c {
case '\b':
b = append(b, '\\', 'b')
case '\f':
b = append(b, '\\', 'f')
case '\n':
b = append(b, '\\', 'n')
case '\r':
b = append(b, '\\', 'r')
case '\t':
b = append(b, '\\', 't')
case '"':
b = append(b, '\\', '"')
case '\\':
b = append(b, '\\', '\\')
default:
// TODO: what about binary gibberish or non UTF-8?
b = append(b, c)
}
}
if nTruncated > 0 {
b = append(b, "…+"...)
b = strconv.AppendInt(b, int64(nTruncated), 10)
}
b = append(b, "\"}\n"...)
return b
}
func (l *Logger) encode(buf []byte, level int) []byte {
if buf[0] != '{' {
return l.encodeText(buf, l.skipClientTime, level) // text fast-path
}
now := l.timeNow()
obj := make(map[string]any)
if err := json.Unmarshal(buf, &obj); err != nil {
for k := range obj {
delete(obj, k)
}
obj["text"] = string(buf)
}
if txt, isStr := obj["text"].(string); l.lowMem && isStr && len(txt) > 254 {
// TODO(crawshaw): trim to unicode code point
obj["text"] = txt[:254] + "…"
}
hasLogtail := obj["logtail"] != nil
if hasLogtail {
obj["error_has_logtail"] = obj["logtail"]
obj["logtail"] = nil
}
if !l.skipClientTime {
obj["logtail"] = map[string]string{
"client_time": now.Format(time.RFC3339Nano),
}
}
if level > 0 {
obj["v"] = level
}
b, err := json.Marshal(obj)
if err != nil {
fmt.Fprintf(l.stderr, "logtail: re-encoding JSON failed: %v\n", err)
// I know of no conditions under which this could fail.
// Report it very loudly.
panic("logtail: re-encoding JSON failed: " + err.Error())
}
b = append(b, '\n')
return b
}
// Logf logs to l using the provided fmt-style format and optional arguments.
func (l *Logger) Logf(format string, args ...any) {
fmt.Fprintf(l, format, args...)
}
// Write logs an encoded JSON blob.
//
// If the []byte passed to Write is not an encoded JSON blob,
// then contents is fit into a JSON blob and written.
//
// This is intended as an interface for the stdlib "log" package.
func (l *Logger) Write(buf []byte) (int, error) {
if len(buf) == 0 {
return 0, nil
}
level, buf := parseAndRemoveLogLevel(buf)
if l.stderr != nil && l.stderr != ioutil.Discard && int64(level) <= atomic.LoadInt64(&l.stderrLevel) {
if buf[len(buf)-1] == '\n' {
l.stderr.Write(buf)
} else {
// The log package always line-terminates logs,
// so this is an uncommon path.
withNL := append(buf[:len(buf):len(buf)], '\n')
l.stderr.Write(withNL)
}
}
b := l.encode(buf, level)
_, err := l.send(b)
return len(buf), err
}
var (
openBracketV = []byte("[v")
v1 = []byte("[v1] ")
v2 = []byte("[v2] ")
vJSON = []byte("[v\x00JSON]") // precedes log level '0'-'9' byte, then JSON value
)
// level 0 is normal (or unknown) level; 1+ are increasingly verbose
func parseAndRemoveLogLevel(buf []byte) (level int, cleanBuf []byte) {
if len(buf) == 0 || buf[0] == '{' || !bytes.Contains(buf, openBracketV) {
return 0, buf
}
if bytes.Contains(buf, v1) {
return 1, bytes.ReplaceAll(buf, v1, nil)
}
if bytes.Contains(buf, v2) {
return 2, bytes.ReplaceAll(buf, v2, nil)
}
if i := bytes.Index(buf, vJSON); i != -1 {
rest := buf[i+len(vJSON):]
if len(rest) >= 2 {
v := rest[0]
if v >= '0' && v <= '9' {
return int(v - '0'), rest[1:]
}
}
}
return 0, buf
}