readme

README.md

@@ -2,5 +2,5 @@
 
 Given source DB,
 
-   1. fully sync to local db
+   1. fully sync from src to dest db
-   1. continuously sync to local db
+   1. continuously sync from src to dest db

go.mod

@@ -1,3 +1,5 @@
 module replicator
 
 go 1.21.1
+
+require gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -0,0 +1,3 @@
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -2,16 +2,67 @@ package main
 
 import (
 	"context"
+	"flag"
+	"net/url"
+	"os"
 	"os/signal"
 	"replicator/replicator"
 	"syscall"
+	"time"
+
+	"gopkg.in/yaml.v3"
 )
 
 func main() {
 	ctx, can := signal.NotifyContext(context.Background(), syscall.SIGINT)
 	defer can()
 
-	if err := replicator.Main(ctx); err != nil && ctx.Err() == nil {
+	config, err := getConfig()
+	if err != nil {
+		panic(err)
+	}
+
+	if err := replicator.Main(ctx, config); err != nil && ctx.Err() == nil {
 		panic(err)
 	}
 }
+
+func getConfig() (replicator.Config, error) {
+	var config replicator.Config
+	if p := os.Getenv("CONFIG"); p != "" {
+		f, err := os.Open(p)
+		if err != nil {
+			return config, err
+		}
+		defer f.Close()
+		if err := yaml.NewDecoder(f).Decode(&config); err != nil {
+			return config, err
+		}
+	}
+
+	var srcDriver, destDriver, interval string
+	flag.StringVar(&srcDriver, "src", "map://", "source db")
+	flag.StringVar(&destDriver, "dest", "map://", "dest db")
+	flag.StringVar(&interval, "interval", "1s", "interval")
+	flag.Parse()
+
+	if srcDriver, err := url.Parse(srcDriver); err != nil {
+		return config, err
+	} else {
+		config.Src.Driver = *srcDriver
+	}
+
+	if destDriver, err := url.Parse(destDriver); err != nil {
+		return config, err
+	} else {
+		config.Dest.Driver = *destDriver
+	}
+
+	if interval, err := time.ParseDuration(interval); err != nil {
+		return config, err
+	} else {
+		config.Interval = replicator.Duration(interval)
+	}
+
+	return config, nil
+}

replicator/config.go

@@ -1,20 +1,53 @@
 package replicator
 
-import "net/url"
+import (
+	"encoding/json"
+	"net/url"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
 
 type (
 	Config struct {
-		Local  Storage
+		Src      Storage
-		Remote Storage
+		Dest     Storage
+		Interval Duration
 	}
 
 	Storage struct {
-		Driver      url.URL
+		Driver url.URL
-		Full        Stream
-		Incremental Stream
 	}
 
-	Stream struct {
+	Duration time.Duration
-		Disabled bool
-	}
 )
+
+func (d *Duration) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	d2, err := time.ParseDuration(s)
+	if err != nil {
+		return err
+	}
+	*d = Duration(d2)
+	return nil
+}
+
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal(time.Duration(d).String())
+}
+
+func (d *Duration) UnmarshalYAML(value *yaml.Node) error {
+	var s string
+	if err := value.Decode(&s); err != nil {
+		return err
+	}
+	b, _ := json.Marshal(s)
+	return d.UnmarshalJSON(b)
+}
+
+func (d Duration) MarshalYAML() (interface{}, error) {
+	return time.Duration(d).String(), nil
+}

replicator/config_test.go

@@ -0,0 +1,30 @@
+package replicator
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+func TestDuration(t *testing.T) {
+	d := Duration(3*time.Second + time.Minute)
+	var d2 Duration
+	if b, err := json.Marshal(d); err != nil {
+		t.Fatal(err)
+	} else if err := json.Unmarshal(b, &d2); err != nil {
+		t.Fatal(err)
+	} else if d != d2 {
+		t.Fatal(d, d2)
+	}
+
+	var d3 Duration
+	if b, err := yaml.Marshal(d); err != nil {
+		t.Fatal(err)
+	} else if err := yaml.Unmarshal(b, &d3); err != nil {
+		t.Fatal(err)
+	} else if d != d3 {
+		t.Fatal(d, d3)
+	}
+}

replicator/driver.go

@@ -1,6 +1,7 @@
 package replicator
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"net/url"
@@ -28,11 +29,11 @@ type (
 
 	KeyVersion struct {
 		Key     Key
-		Version []byte
+		Version Version
 	}
 
 	ValueVersion struct {
-		Value   []byte
+		Value   Value
 		Version Version
 	}
 )
@@ -64,3 +65,15 @@ func TimeAsVersion(t time.Time) Version {
 	n := t.UnixNano()
 	return []byte(strconv.FormatInt(n, 10))
 }
+
+func (version Version) Equal(other Version) bool {
+	return bytes.Equal(version, other)
+}
+
+func (key Key) Equal(other Key) bool {
+	return key == other
+}
+
+func (value Value) Equal(other Value) bool {
+	return bytes.Equal(value, other)
+}

replicator/driver_test.go

@@ -10,6 +10,7 @@ import (
 func TestDriverInterface(t *testing.T) {
 	var _ Driver = FileTree("")
 	var _ Driver = Map{}
+	var _ Driver = Must{}
 }
 
 func testDriver(t *testing.T, d Driver) {

replicator/main.go

@@ -2,9 +2,19 @@ package replicator
 
 import (
 	"context"
-	"errors"
 )
 
-func Main(ctx context.Context) error {
+func Main(ctx context.Context, config Config) error {
-	return errors.New("not impl")
+	src, err := NewDriver(ctx, config.Src.Driver)
+	if err != nil {
+		return err
+	}
+
+	dest, err := NewDriver(ctx, config.Dest.Driver)
+	if err != nil {
+		return err
+	}
+
+	replicator := NewReplicator(dest, src)
+	return replicator.Stream(ctx)
 }

replicator/must.go

@@ -0,0 +1,40 @@
+package replicator
+
+import (
+	"context"
+	"time"
+)
+
+type Must struct {
+	driver Driver
+}
+
+func NewMust(driver Driver) Must {
+	return Must{driver: driver}
+}
+
+func (must Must) KeysSince(ctx context.Context, t time.Time) (chan KeyVersion, *error) {
+	return must.driver.KeysSince(ctx, t)
+}
+
+func (must Must) Get(ctx context.Context, k Key) (ValueVersion, error) {
+	got, err := must.driver.Get(ctx, k)
+	if err != nil {
+		panic(err)
+	}
+	return got, nil
+}
+
+func (must Must) Set(ctx context.Context, k Key, v Value, ver Version) error {
+	if err := must.driver.Set(ctx, k, v, ver); err != nil {
+		panic(err)
+	}
+	return nil
+}
+
+func (must Must) Del(ctx context.Context, k Key, ver Version) error {
+	if err := must.driver.Del(ctx, k, ver); err != nil {
+		panic(err)
+	}
+	return nil
+}

replicator/replicator.go

@@ -2,21 +2,88 @@ package replicator
 
 import (
 	"context"
-	"io"
+	"time"
 )
 
 type Replicator struct {
-	Src  Driver
+	Src      Driver
-	Dest Driver
+	Dest     Driver
+	Interval time.Duration
 }
 
-func NewReplicator(src, dest Driver) Replicator {
+func NewReplicator(dest, src Driver) Replicator {
 	return Replicator{
-		Src:  src,
+		Src:      src,
-		Dest: dest,
+		Dest:     dest,
+		Interval: time.Second,
 	}
 }
 
 func (r Replicator) Stream(ctx context.Context) error {
-	return io.EOF
+	last, err := r.getContinuation(ctx)
+	if err != nil {
+		return err
+	}
+	if last == nil {
+		if err := r.fullStream(ctx); err != nil {
+			return err
+		}
+	}
+	return r.deltaStream(ctx)
+}
+
+func (r Replicator) getContinuation(ctx context.Context) (Version, error) {
+	return nil, nil // TODO
+}
+
+func (r Replicator) setContinuation(ctx context.Context, continuation Version) error {
+	return nil // TODO
+}
+
+func (r Replicator) deltaStream(ctx context.Context) error {
+	continuation, err := r.getContinuation(ctx)
+	if err != nil {
+		return err
+	}
+	for ctx.Err() == nil {
+		if err := r._deltaStream(ctx, continuation); err != nil {
+			return err
+		}
+		select {
+		case <-ctx.Done():
+		case <-time.After(r.Interval):
+		}
+	}
+	return ctx.Err()
+}
+
+func (r Replicator) _deltaStream(ctx context.Context, continuation Version) error {
+	last, err := continuation.AsTime()
+	if err != nil {
+		return err
+	}
+	keys, after := r.Src.KeysSince(ctx, last)
+	for keyVersion := range keys {
+		if t, err := keyVersion.Version.AsTime(); err != nil {
+			return err
+		} else if t.After(last) {
+			last = t
+		}
+
+		valueVersion, err := r.Src.Get(ctx, keyVersion.Key)
+		if err != nil {
+			return err
+		}
+
+		if err := r.Dest.Set(ctx, keyVersion.Key, valueVersion.Value, valueVersion.Version); err != nil {
+			return err
+		}
+
+		r.setContinuation(ctx, TimeAsVersion(last))
+	}
+	return *after
+}
+
+func (r Replicator) fullStream(ctx context.Context) error {
+	return r._deltaStream(ctx, nil)
 }

replicator/replicator_test.go

@@ -0,0 +1,93 @@
+package replicator
+
+import (
+	"context"
+	"errors"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestReplicatorStream(t *testing.T) {
+	t.Parallel()
+
+	key := Key{Namespace: "x/y", Key: "z"}
+	value := Value("hello world")
+	oldVersion := TimeAsVersion(time.Now().Add(-1 * time.Hour))
+	version := TimeAsVersion(time.Now())
+
+	cases := map[string]struct {
+		before func(*testing.T, Replicator)
+		during func(*testing.T, Replicator)
+		after  func(*testing.T, Replicator)
+	}{
+		"noop": {},
+		"one prior op moves": {
+			before: func(t *testing.T, r Replicator) {
+				r.Src.Set(nil, key, value, version)
+			},
+			after: func(t *testing.T, r Replicator) {
+				if got, _ := r.Dest.Get(nil, key); !got.Version.Equal(version) || !got.Value.Equal(value) {
+					t.Error(got)
+				}
+			},
+		},
+		"one during op moves": {
+			during: func(t *testing.T, r Replicator) {
+				r.Src.Set(nil, key, value, version)
+			},
+			after: func(t *testing.T, r Replicator) {
+				if got, _ := r.Dest.Get(nil, key); !got.Version.Equal(version) || !got.Value.Equal(value) {
+					t.Error(got)
+				}
+			},
+		},
+		"dont overwrite newer received later": {
+			before: func(t *testing.T, r Replicator) {
+				r.Dest.Set(nil, key, value, version)
+			},
+			during: func(t *testing.T, r Replicator) {
+				r.Src.Set(nil, key, value, oldVersion)
+			},
+			after: func(t *testing.T, r Replicator) {
+				if got, _ := r.Dest.Get(nil, key); !got.Version.Equal(version) || !got.Value.Equal(value) {
+					t.Error(got)
+				}
+			},
+		},
+	}
+
+	for name, d := range cases {
+		c := d
+		t.Run(name, func(t *testing.T) {
+			replicator := NewReplicator(NewMust(NewMap()), NewMust(NewMap()))
+			replicator.Interval = time.Millisecond * 10
+			ctx, can := context.WithTimeout(context.Background(), time.Second*10)
+			defer can()
+
+			if c.before != nil {
+				c.before(t, replicator)
+			}
+
+			wg := &sync.WaitGroup{}
+			wg.Add(1)
+			go func(t *testing.T) {
+				defer wg.Done()
+				if err := replicator.Stream(ctx); err != nil && !errors.Is(err, ctx.Err()) {
+					t.Error(err)
+				}
+			}(t)
+			time.Sleep(time.Millisecond * 150)
+			if c.during != nil {
+				c.during(t, replicator)
+			}
+			time.Sleep(time.Millisecond * 150)
+
+			can()
+			wg.Wait()
+			if c.after != nil {
+				c.after(t, replicator)
+			}
+		})
+	}
+}