feature/logtail: pull logtail + netlog out to modular features

Removes 434 KB from the minimal Linux binary, or ~3%.

Primarily this comes from not linking in the zstd encoding code.

Fixes #17323

Change-Id: I0a90de307dfa1ad7422db7aa8b1b46c782bfaaf7
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

logtail/buffer.go

@@ -1,6 +1,8 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+//go:build !ts_omit_logtail
+
 package logtail
 
 import (

logtail/config.go

@@ -0,0 +1,65 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package logtail
+
+import (
+	"io"
+	"net/http"
+	"time"
+
+	"tailscale.com/tstime"
+	"tailscale.com/types/logid"
+)
+
+// DefaultHost is the default host name to upload logs to when
+// Config.BaseURL isn't provided.
+const DefaultHost = "log.tailscale.com"
+
+const defaultFlushDelay = 2 * time.Second
+
+const (
+	// CollectionNode is the name of a logtail Config.Collection
+	// for tailscaled (or equivalent: IPNExtension, Android app).
+	CollectionNode = "tailnode.log.tailscale.io"
+)
+
+type Config struct {
+	Collection     string          // collection name, a domain name
+	PrivateID      logid.PrivateID // private ID for the primary log stream
+	CopyPrivateID  logid.PrivateID // private ID for a log stream that is a superset of this log stream
+	BaseURL        string          // if empty defaults to "https://log.tailscale.com"
+	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
+	Clock          tstime.Clock    // if set, Clock.Now substitutes 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
+	CompressLogs   bool            // whether to compress the log uploads
+	MaxUploadSize  int             // maximum upload size; 0 means using the default
+
+	// 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
+
+	// FlushDelayFn, if non-nil is a func that returns how long to wait to
+	// accumulate logs before uploading them. 0 or negative means to upload
+	// immediately.
+	//
+	// If nil, a default value is used. (currently 2 seconds)
+	FlushDelayFn func() time.Duration
+
+	// IncludeProcID, if true, results in an ephemeral process identifier being
+	// included in logs. The ID is random and not guaranteed to be globally
+	// unique, but it can be used to distinguish between different instances
+	// running with same PrivateID.
+	IncludeProcID bool
+
+	// IncludeProcSequence, if true, results in an ephemeral sequence number
+	// being included in the logs. The sequence number is incremented for each
+	// log message sent, but is not persisted across process restarts.
+	IncludeProcSequence bool
+}

logtail/logtail.go

@@ -1,6 +1,8 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+//go:build !ts_omit_logtail
+
 // Package logtail sends logs to log.tailscale.com.
 package logtail
 
@@ -51,58 +53,6 @@ const lowMemRatio = 4
 // but not too large to be a notable waste of memory if retained forever.
 const bufferSize = 4 << 10
 
-// DefaultHost is the default host name to upload logs to when
-// Config.BaseURL isn't provided.
-const DefaultHost = "log.tailscale.com"
-
-const defaultFlushDelay = 2 * time.Second
-
-const (
-	// CollectionNode is the name of a logtail Config.Collection
-	// for tailscaled (or equivalent: IPNExtension, Android app).
-	CollectionNode = "tailnode.log.tailscale.io"
-)
-
-type Config struct {
-	Collection     string          // collection name, a domain name
-	PrivateID      logid.PrivateID // private ID for the primary log stream
-	CopyPrivateID  logid.PrivateID // private ID for a log stream that is a superset of this log stream
-	BaseURL        string          // if empty defaults to "https://log.tailscale.com"
-	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
-	Clock          tstime.Clock    // if set, Clock.Now substitutes 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
-	CompressLogs   bool            // whether to compress the log uploads
-	MaxUploadSize  int             // maximum upload size; 0 means using the default
-
-	// 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
-
-	// FlushDelayFn, if non-nil is a func that returns how long to wait to
-	// accumulate logs before uploading them. 0 or negative means to upload
-	// immediately.
-	//
-	// If nil, a default value is used. (currently 2 seconds)
-	FlushDelayFn func() time.Duration
-
-	// IncludeProcID, if true, results in an ephemeral process identifier being
-	// included in logs. The ID is random and not guaranteed to be globally
-	// unique, but it can be used to distinguish between different instances
-	// running with same PrivateID.
-	IncludeProcID bool
-
-	// IncludeProcSequence, if true, results in an ephemeral sequence number
-	// being included in the logs. The sequence number is incremented for each
-	// log message sent, but is not persisted across process restarts.
-	IncludeProcSequence bool
-}
-
 func NewLogger(cfg Config, logf tslogger.Logf) *Logger {
 	if cfg.BaseURL == "" {
 		cfg.BaseURL = "https://" + DefaultHost

logtail/logtail_omit.go

@@ -0,0 +1,44 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ts_omit_logtail
+
+package logtail
+
+import (
+	"context"
+
+	tslogger "tailscale.com/types/logger"
+	"tailscale.com/types/logid"
+)
+
+// Noop implementations of everything when ts_omit_logtail is set.
+
+type Logger struct{}
+
+type Buffer any
+
+func Disable() {}
+
+func NewLogger(cfg Config, logf tslogger.Logf) *Logger {
+	return &Logger{}
+}
+
+func (*Logger) Write(p []byte) (n int, err error) {
+	return len(p), nil
+}
+
+func (*Logger) Logf(format string, args ...any)    {}
+func (*Logger) Shutdown(ctx context.Context) error { return nil }
+func (*Logger) SetVerbosityLevel(level int)        {}
+
+func (l *Logger) SetSockstatsLabel(label any) {}
+
+func (l *Logger) PrivateID() logid.PrivateID { return logid.PrivateID{} }
+func (l *Logger) StartFlush()                {}
+
+func RegisterLogTap(dst chan<- string) (unregister func()) {
+	return func() {}
+}
+
+func (*Logger) SetNetMon(any) {}