refactor(netx): merge archival, trace, and the savers (#772)

This diff creates a new package under netx called tracex that
contains everything we need to perform measurements using events
tracing and postprocessing (which is the technique with which
we implement most network experiments).

The general idea here is to (1) create a unique package out of
all of these packages; (2) clean up the code a bit (improve tests,
docs, apply more recent code patterns); (3) move the resulting
code as a toplevel package inside of internal.

Once this is done, netx can be further refactored to avoid
subpackages and we can search for more code to salvage/refactor.

See https://github.com/ooni/probe/issues/2121

internal/engine/netx/dialer/dialer.go

@@ -7,7 +7,7 @@ import (
 	"net/url"
 
 	"github.com/ooni/probe-cli/v3/internal/bytecounter"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/tracex"
 	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
@@ -35,7 +35,7 @@ type Config struct {
 
 	// DialSaver is the optional saver for dialing events. If not
 	// set, we will not save any dialing event.
-	DialSaver *trace.Saver
+	DialSaver *tracex.Saver
 
 	// Logger is the optional logger. If not set, there
 	// will be no logging from the new dialer.
@@ -45,7 +45,7 @@ type Config struct {
 	ProxyURL *url.URL
 
 	// ReadWriteSaver is like DialSaver but for I/O events.
-	ReadWriteSaver *trace.Saver
+	ReadWriteSaver *tracex.Saver
 }
 
 // New creates a new Dialer from the specified config and resolver.
@@ -57,13 +57,13 @@ func New(config *Config, resolver model.Resolver) model.Dialer {
 	modifiers := []netxlite.DialerWrapper{
 		func(dialer model.Dialer) model.Dialer {
 			if config.DialSaver != nil {
-				dialer = &saverDialer{Dialer: dialer, Saver: config.DialSaver}
+				dialer = &tracex.SaverDialer{Dialer: dialer, Saver: config.DialSaver}
 			}
 			return dialer
 		},
 		func(dialer model.Dialer) model.Dialer {
 			if config.ReadWriteSaver != nil {
-				dialer = &saverConnDialer{Dialer: dialer, Saver: config.ReadWriteSaver}
+				dialer = &tracex.SaverConnDialer{Dialer: dialer, Saver: config.ReadWriteSaver}
 			}
 			return dialer
 		},

internal/engine/netx/dialer/dialer_test.go

@@ -7,12 +7,12 @@ import (
 
 	"github.com/apex/log"
 	"github.com/ooni/probe-cli/v3/internal/bytecounter"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/tracex"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestNewCreatesTheExpectedChain(t *testing.T) {
-	saver := &trace.Saver{}
+	saver := &tracex.Saver{}
 	dlr := New(&Config{
 		ContextByteCounting: true,
 		DialSaver:           saver,

internal/engine/netx/dialer/saver.go

@@ -1,88 +0,0 @@
-package dialer
-
-import (
-	"context"
-	"net"
-	"time"
-
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
-	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-// saverDialer saves events occurring during the dial
-type saverDialer struct {
-	model.Dialer
-	Saver *trace.Saver
-}
-
-// DialContext implements Dialer.DialContext
-func (d *saverDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
-	start := time.Now()
-	conn, err := d.Dialer.DialContext(ctx, network, address)
-	stop := time.Now()
-	d.Saver.Write(trace.Event{
-		Address:  address,
-		Duration: stop.Sub(start),
-		Err:      err,
-		Name:     netxlite.ConnectOperation,
-		Proto:    network,
-		Time:     stop,
-	})
-	return conn, err
-}
-
-// saverConnDialer wraps the returned connection such that we
-// collect all the read/write events that occur.
-type saverConnDialer struct {
-	model.Dialer
-	Saver *trace.Saver
-}
-
-// DialContext implements Dialer.DialContext
-func (d *saverConnDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
-	conn, err := d.Dialer.DialContext(ctx, network, address)
-	if err != nil {
-		return nil, err
-	}
-	return &saverConn{saver: d.Saver, Conn: conn}, nil
-}
-
-type saverConn struct {
-	net.Conn
-	saver *trace.Saver
-}
-
-func (c *saverConn) Read(p []byte) (int, error) {
-	start := time.Now()
-	count, err := c.Conn.Read(p)
-	stop := time.Now()
-	c.saver.Write(trace.Event{
-		Data:     p[:count],
-		Duration: stop.Sub(start),
-		Err:      err,
-		NumBytes: count,
-		Name:     netxlite.ReadOperation,
-		Time:     stop,
-	})
-	return count, err
-}
-
-func (c *saverConn) Write(p []byte) (int, error) {
-	start := time.Now()
-	count, err := c.Conn.Write(p)
-	stop := time.Now()
-	c.saver.Write(trace.Event{
-		Data:     p[:count],
-		Duration: stop.Sub(start),
-		Err:      err,
-		NumBytes: count,
-		Name:     netxlite.WriteOperation,
-		Time:     stop,
-	})
-	return count, err
-}
-
-var _ model.Dialer = &saverDialer{}
-var _ model.Dialer = &saverConnDialer{}
-var _ net.Conn = &saverConn{}

internal/engine/netx/dialer/saver_test.go

@@ -1,139 +0,0 @@
-package dialer
-
-import (
-	"context"
-	"errors"
-	"io"
-	"net"
-	"testing"
-	"time"
-
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
-	"github.com/ooni/probe-cli/v3/internal/model/mocks"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-func TestSaverDialerFailure(t *testing.T) {
-	expected := errors.New("mocked error")
-	saver := &trace.Saver{}
-	dlr := &saverDialer{
-		Dialer: &mocks.Dialer{
-			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
-				return nil, expected
-			},
-		},
-		Saver: saver,
-	}
-	conn, err := dlr.DialContext(context.Background(), "tcp", "www.google.com:443")
-	if !errors.Is(err, expected) {
-		t.Fatal("expected another error here")
-	}
-	if conn != nil {
-		t.Fatal("expected nil conn here")
-	}
-	ev := saver.Read()
-	if len(ev) != 1 {
-		t.Fatal("expected a single event here")
-	}
-	if ev[0].Address != "www.google.com:443" {
-		t.Fatal("unexpected Address")
-	}
-	if ev[0].Duration <= 0 {
-		t.Fatal("unexpected Duration")
-	}
-	if !errors.Is(ev[0].Err, expected) {
-		t.Fatal("unexpected Err")
-	}
-	if ev[0].Name != netxlite.ConnectOperation {
-		t.Fatal("unexpected Name")
-	}
-	if ev[0].Proto != "tcp" {
-		t.Fatal("unexpected Proto")
-	}
-	if !ev[0].Time.Before(time.Now()) {
-		t.Fatal("unexpected Time")
-	}
-}
-
-func TestSaverConnDialerFailure(t *testing.T) {
-	expected := errors.New("mocked error")
-	saver := &trace.Saver{}
-	dlr := &saverConnDialer{
-		Dialer: &mocks.Dialer{
-			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
-				return nil, expected
-			},
-		},
-		Saver: saver,
-	}
-	conn, err := dlr.DialContext(context.Background(), "tcp", "www.google.com:443")
-	if !errors.Is(err, expected) {
-		t.Fatal("not the error we expected")
-	}
-	if conn != nil {
-		t.Fatal("expected nil conn here")
-	}
-}
-
-func TestSaverConnDialerSuccess(t *testing.T) {
-	saver := &trace.Saver{}
-	dlr := &saverConnDialer{
-		Dialer: &saverDialer{
-			Dialer: &mocks.Dialer{
-				MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
-					return &mocks.Conn{
-						MockRead: func(b []byte) (int, error) {
-							return 0, io.EOF
-						},
-						MockWrite: func(b []byte) (int, error) {
-							return 0, io.EOF
-						},
-						MockClose: func() error {
-							return io.EOF
-						},
-						MockLocalAddr: func() net.Addr {
-							return &net.TCPAddr{Port: 12345}
-						},
-					}, nil
-				},
-			},
-			Saver: saver,
-		},
-		Saver: saver,
-	}
-	conn, err := dlr.DialContext(context.Background(), "tcp", "www.google.com:443")
-	if err != nil {
-		t.Fatal("not the error we expected", err)
-	}
-	conn.Read(nil)
-	conn.Write(nil)
-	conn.Close()
-	events := saver.Read()
-	if len(events) != 3 {
-		t.Fatal("unexpected number of events saved", len(events))
-	}
-	if events[0].Name != "connect" {
-		t.Fatal("expected a connect event")
-	}
-	saverCheckConnectEvent(t, &events[0])
-	if events[1].Name != "read" {
-		t.Fatal("expected a read event")
-	}
-	saverCheckReadEvent(t, &events[1])
-	if events[2].Name != "write" {
-		t.Fatal("expected a write event")
-	}
-	saverCheckWriteEvent(t, &events[2])
-}
-
-func saverCheckConnectEvent(t *testing.T, ev *trace.Event) {
-	// TODO(bassosimone): implement
-}
-
-func saverCheckReadEvent(t *testing.T, ev *trace.Event) {
-	// TODO(bassosimone): implement
-}
-
-func saverCheckWriteEvent(t *testing.T, ev *trace.Event) {
-	// TODO(bassosimone): implement
-}