Add state provider

FerretDB · AlekSi · Oct 12, 2022 · Oct 10, 2022 · Oct 10, 2022 · Oct 11, 2022
commit 4ab5f84a69ecaa24ff59aa8119d51748164603fb
diff --git a/.gitignore b/.gitignore
@@ -22,6 +22,9 @@ node_modules/
 # test coverage results, generated files like commit.txt, etc.
 *.txt
 
+# runtime state
+state.json
+
 # for now
 testdata/fuzz/
 records/

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -32,6 +33,7 @@ import (
 	"github.com/FerretDB/FerretDB/internal/handlers/registry"
 	"github.com/FerretDB/FerretDB/internal/util/debug"
 	"github.com/FerretDB/FerretDB/internal/util/logging"
+	"github.com/FerretDB/FerretDB/internal/util/state"
 	"github.com/FerretDB/FerretDB/internal/util/version"
 )
 
@@ -42,9 +44,9 @@ var cli struct {
 	ProxyAddr  string `default:"127.0.0.1:37017"      help:"Proxy address."`
 	DebugAddr  string `default:"127.0.0.1:8088"       help:"Debug address."`
 	LogLevel   string `default:"${default_log_level}" help:"${help_log_level}"`
-	Mode       string `default:"${default_mode}"      help:"${help_mode}"      enum:"${enum_mode}"`
-
-	Handler string `default:"pg" help:"${help_handler}"`
+	StateDir   string `default:"."                    help:"Process state directory."`
+	Mode       string `default:"${default_mode}"      help:"${help_mode}"             enum:"${enum_mode}"`
+	Handler    string `default:"pg"                   help:"${help_handler}"`
 
 	PostgresURL string `default:"postgres://postgres@127.0.0.1:5432/ferretdb" help:"PostgreSQL URL for 'pg' handler."`
 
@@ -54,8 +56,8 @@ var cli struct {
 	Version bool `default:"false" help:"Print version to stdout and exit."`
 
 	Test struct {
-		ConnTimeout time.Duration `default:"0" help:"For testing: client connection timeout."`
-		RecordsDir  string        `default:""  help:"For testing: directory for record files."`
+		ConnTimeout time.Duration `default:"0" help:"Testing flag: client connection timeout."`
+		RecordsDir  string        `default:""  help:"Testing flag: directory for record files."`
 	} `embed:"" prefix:"test-"`
 }
 
@@ -116,13 +118,30 @@ func run() {
 		return
 	}
 
+	stateFile, err := filepath.Abs(filepath.Join(cli.StateDir, "state.json"))
+	if err != nil {
+		logger.Fatal("Failed to get path for state file", zap.Error(err))
+	}
+	logger.Debug("State file", zap.String("filename", stateFile))
+
+	p, err := state.NewProvider(stateFile)
+	if err != nil {
+		logger.Fatal("Failed to create state provider", zap.Error(err))
+	}
+
+	s, err := p.Get()
+	if err != nil {
+		logger.Fatal("Failed to get state", zap.Error(err))
+	}
+
 	startFields := []zap.Field{
 		zap.String("version", info.Version),
 		zap.String("commit", info.Commit),
 		zap.String("branch", info.Branch),
 		zap.Bool("dirty", info.Dirty),
 		zap.Bool("debug", info.Debug),
 		zap.Reflect("buildEnvironment", info.BuildEnvironment.Map()),
+		zap.String("uuid", s.UUID),
 	}
 	logger.Info("Starting FerretDB "+info.Version+"...", startFields...)
 

diff --git a/go.mod b/go.mod
@@ -5,6 +5,7 @@ go 1.19
 require (
 	github.com/AlekSi/pointer v1.2.0
 	github.com/alecthomas/kong v0.6.1
+	github.com/google/uuid v1.3.0
 	github.com/jackc/pgconn v1.13.0
 	github.com/jackc/pgerrcode v0.0.0-20220416144525-469b46aa5efa
 	github.com/jackc/pgx/v4 v4.17.2
@@ -33,7 +34,6 @@ require (
 	github.com/go-openapi/swag v0.21.1 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/google/gnostic v0.6.9 // indirect
-	github.com/google/uuid v1.3.0 // indirect
 	github.com/grpc-ecosystem/go-grpc-middleware v1.3.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.10.2 // indirect
 	github.com/jackc/chunkreader/v2 v2.0.1 // indirect

@@ -157,7 +157,7 @@ func (c *conn) run(ctx context.Context) (err error) {
 
 	// if test record path is set, split netConn reader to write to file and bufr
 	if c.testRecordsDir != "" {
-		if err := os.MkdirAll(c.testRecordsDir, 0o755); err != nil {
+		if err := os.MkdirAll(c.testRecordsDir, 0o777); err != nil {
 			return err
 		}
 

@@ -0,0 +1,103 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package state stores FerretDB process state.
+package state
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/google/uuid"
+
+	"github.com/FerretDB/FerretDB/internal/util/must"
+)
+
+// State represents FerretDB process state.
+type State struct {
+	UUID string `json:"uuid"`
+}
+
+// Provider provides access to FerretDB process state.
+type Provider struct {
+	filename string
+
+	rw sync.RWMutex
+	s  State
+}
+
+// NewProvider creates a new Provider that stores state in the given file.
+func NewProvider(filename string) (*Provider, error) {
+	p := &Provider{
+		filename: filename,
+	}
+
+	if _, err := p.Get(); err != nil {
+		return nil, err
+	}
+
+	return p, nil
+}
+
+// Get returns the current process state.
+//
+// It is okay to call this function often.
+// The caller should not cache result; Provider does everything needed itself.
+func (p *Provider) Get() (*State, error) {
+	// return different copies to each caller
+	p.rw.RLock()
+	s := p.s
+	p.rw.RUnlock()
+
+	if s.UUID != "" {
+		return &s, nil
+	}
+
+	// happy path: try to read UUID, ignore all errors
+
+	b, _ := os.ReadFile(p.filename)
+	_ = json.Unmarshal(b, &s)
+
+	if s.UUID != "" {
+		// store a copy
+		p.rw.Lock()
+		p.s = s
+		p.rw.Unlock()
+
+		return &s, nil
+	}
+
+	// regenerate and save UUID if any error occurred
+
+	s.UUID = must.NotFail(uuid.NewRandom()).String()
+	b = must.NotFail(json.Marshal(s))
+
+	if err := os.MkdirAll(filepath.Dir(p.filename), 0o777); err != nil && !os.IsExist(err) {
+		return nil, fmt.Errorf("failed to create state directory: %w", err)
+	}
+
+	if err := os.WriteFile(p.filename, b, 0o666); err != nil {
+		return nil, fmt.Errorf("failed to write state file: %w", err)
+	}
+
+	// store a copy
+	p.rw.Lock()
+	p.s = s
+	p.rw.Unlock()
+
+	return &s, nil
+}
@@ -0,0 +1,61 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package state
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestState(t *testing.T) {
+	filename := filepath.Join(t.TempDir(), "state.json")
+	p1, err := NewProvider(filename)
+	require.NoError(t, err)
+
+	s1, err := p1.Get()
+	require.NoError(t, err)
+	assert.NotEmpty(t, s1.UUID)
+
+	s2, err := p1.Get()
+	require.NoError(t, err)
+	assert.Equal(t, s1, s2)
+	assert.NotSame(t, s1, s2)
+
+	s3, err := p1.Get()
+	require.NoError(t, err)
+	assert.Equal(t, s1, s3)
+	assert.NotSame(t, s1, s3)
+
+	p2, err := NewProvider(filename)
+	require.NoError(t, err)
+
+	s4, err := p2.Get()
+	require.NoError(t, err)
+	assert.Equal(t, s1, s4)
+	assert.NotSame(t, s1, s4)
+
+	require.NoError(t, os.Remove(filename))
+
+	p3, err := NewProvider(filename)
+	require.NoError(t, err)
+
+	s5, err := p3.Get()
+	require.NoError(t, err)
+	assert.NotEqual(t, s1, s5)
+}
diff --git a/internal/util/version/generate.go b/internal/util/version/generate.go
@@ -50,7 +50,7 @@ func main() {
 		defer wg.Done()
 
 		b := runGit("describe", "--tags", "--dirty")
-		must.NoError(os.WriteFile(filepath.Join("gen", "version.txt"), b, 0o644))
+		must.NoError(os.WriteFile(filepath.Join("gen", "version.txt"), b, 0o666))
 	}()
 
 	// git rev-parse HEAD > gen/commit.txt
@@ -59,7 +59,7 @@ func main() {
 		defer wg.Done()
 
 		b := runGit("rev-parse", "HEAD")
-		must.NoError(os.WriteFile(filepath.Join("gen", "commit.txt"), b, 0o644))
+		must.NoError(os.WriteFile(filepath.Join("gen", "commit.txt"), b, 0o666))
 	}()
 
 	// git branch --show-current > gen/branch.txt
@@ -68,7 +68,7 @@ func main() {
 		defer wg.Done()
 
 		b := runGit("branch", "--show-current")
-		must.NoError(os.WriteFile(filepath.Join("gen", "branch.txt"), b, 0o644))
+		must.NoError(os.WriteFile(filepath.Join("gen", "branch.txt"), b, 0o666))
 	}()
 
 	wg.Wait()