Issue #6 | Add SqlServer support | Adarsh

sqlserver/sqlserver.go

@@ -0,0 +1,277 @@
+package sqlserver
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/italolelis/outboxer"
+	"github.com/italolelis/outboxer/lock"
+)
+
+const (
+	// DefaultEventStoreTable is the default table name
+	DefaultEventStoreTable = "event_store"
+)
+
+var (
+	// ErrLocked is used when we can't acquire an explicit lock
+	ErrLocked = errors.New("can't acquire lock")
+
+	// ErrNoDatabaseName is used when the database name is blank
+	ErrNoDatabaseName = errors.New("no database name")
+
+	// ErrNoSchema is used when the schema name is blank
+	ErrNoSchema = errors.New("no schema")
+)
+
+// SQLServer implementation of the data store
+type SQLServer struct {
+	conn     *sql.Conn
+	isLocked bool
+
+	SchemaName      string
+	DatabaseName    string
+	EventStoreTable string
+}
+
+// WithInstance creates a SQLServer data store with an existing db connection
+func WithInstance(ctx context.Context, db *sql.DB) (*SQLServer, error) {
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	s := SQLServer{conn: conn}
+
+	if err := conn.QueryRowContext(ctx, `SELECT DB_NAME()`).Scan(&s.DatabaseName); err != nil {
+		return nil, err
+	}
+
+	if len(s.DatabaseName) == 0 {
+		return nil, ErrNoDatabaseName
+	}
+
+	if err := conn.QueryRowContext(ctx, `SELECT SCHEMA_NAME()`).Scan(&s.SchemaName); err != nil {
+		return nil, err
+	}
+
+	if len(s.SchemaName) == 0 {
+		return nil, ErrNoSchema
+	}
+
+	if len(s.EventStoreTable) == 0 {
+		s.EventStoreTable = DefaultEventStoreTable
+	}
+
+	if err := s.ensureTable(ctx); err != nil {
+		return nil, err
+	}
+
+	return &s, nil
+}
+
+// Close closes the db connection
+func (s *SQLServer) Close() error {
+	if err := s.conn.Close(); err != nil {
+		return fmt.Errorf("failed to close connection: %w", err)
+	}
+	return nil
+}
+
+// Add the message to the data store
+func (s *SQLServer) Add(ctx context.Context, evt *outboxer.OutboxMessage) error {
+	query := fmt.Sprintf(`INSERT INTO [%s].[%s] (payload, options, headers) VALUES (@p1, @p2, @p3)`, s.SchemaName, s.EventStoreTable)
+	if _, err := s.conn.ExecContext(ctx, query, evt.Payload, checkBinaryParam(evt.Options), checkBinaryParam(evt.Headers)); err != nil {
+		return fmt.Errorf("failed to insert message into the data store: %w", err)
+	}
+
+	return nil
+}
+
+// AddWithinTx creates a transaction and then tries to execute anything within it
+func (s *SQLServer) AddWithinTx(ctx context.Context, evt *outboxer.OutboxMessage, fn func(outboxer.ExecerContext) error) error {
+	tx, err := s.conn.BeginTx(ctx, &sql.TxOptions{})
+	if err != nil {
+		return fmt.Errorf("transaction start failed: %w", err)
+	}
+
+	err = fn(tx)
+	if err != nil {
+		return err
+	}
+
+	query := fmt.Sprintf(`INSERT INTO [%s].[%s] (payload, options, headers) VALUES (@p1, @p2, @p3)`, s.SchemaName, s.EventStoreTable)
+
+	if _, err := tx.ExecContext(ctx, query, evt.Payload, checkBinaryParam(evt.Options), checkBinaryParam(evt.Headers)); err != nil {
+		tx.Rollback()
+		return fmt.Errorf("failed to insert message into the data store: %w", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("transaction commit failed: %w", err)
+	}
+
+	return nil
+}
+
+//checkBinaryParam is a fix for issue with mssql driver converting nil value in varbinary to nvarchar.
+//https://github.com/denisenkom/go-mssqldb/issues/530
+func checkBinaryParam(p outboxer.DynamicValues) outboxer.DynamicValues {
+	if p == nil {
+		return map[string]interface{}{}
+	}
+	return p
+}
+
+// SetAsDispatched sets one message as dispatched
+func (s *SQLServer) SetAsDispatched(ctx context.Context, id int64) error {
+	query := fmt.Sprintf(`
+UPDATE [%s].[%s]
+SET
+    dispatched = 1,
+    dispatched_at = GETDATE(),
+    options = null,
+	headers = null
+WHERE id = @p1;
+`, s.SchemaName, s.EventStoreTable)
+	if _, err := s.conn.ExecContext(ctx, query, id); err != nil {
+		return fmt.Errorf("failed to set message as dispatched: %w", err)
+	}
+
+	return nil
+}
+
+// Remove removes old messages from the data store
+func (s *SQLServer) Remove(ctx context.Context, dispatchedBefore time.Time, batchSize int32) error {
+	tx, err := s.conn.BeginTx(ctx, &sql.TxOptions{})
+	if err != nil {
+		return fmt.Errorf("transaction start failed: %w", err)
+	}
+
+	q := `
+DELETE FROM [%[1]s].[%[2]s]
+WHERE id IN
+(
+    SELECT TOP %d id
+    FROM %[%[1]s].[%[2]s]
+    WHERE
+        "dispatched" = true AND
+        "dispatched_at" < @p1
+)
+`
+
+	query := fmt.Sprintf(q, s.SchemaName, s.EventStoreTable, batchSize)
+	if _, err := tx.ExecContext(ctx, query, dispatchedBefore); err != nil {
+		tx.Rollback()
+		return fmt.Errorf("failed to remove messages from the data store: %w", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("transaction commit failed: %w", err)
+	}
+
+	return nil
+}
+
+// GetEvents retrieves all the relevant events
+func (s *SQLServer) GetEvents(ctx context.Context, batchSize int32) ([]*outboxer.OutboxMessage, error) {
+	var events []*outboxer.OutboxMessage
+
+	rows, err := s.conn.QueryContext(ctx, fmt.Sprintf("SELECT TOP %d * FROM [%s].[%s] WHERE dispatched = 0", batchSize, s.SchemaName, s.EventStoreTable))
+	if err != nil {
+		return events, fmt.Errorf("failed to get messages from the store: %w", err)
+	}
+
+	for rows.Next() {
+		var e outboxer.OutboxMessage
+		err = rows.Scan(&e.ID, &e.Dispatched, &e.DispatchedAt, &e.Payload, &e.Options, &e.Headers)
+		if err != nil {
+			return events, fmt.Errorf("failed to scan message: %w", err)
+		}
+		events = append(events, &e)
+	}
+
+	return events, nil
+}
+
+// Lock implements explicit locking
+func (s *SQLServer) lock(ctx context.Context) error {
+	if s.isLocked {
+		return ErrLocked
+	}
+
+	aid, err := lock.Generate(s.DatabaseName, s.SchemaName)
+	if err != nil {
+		return err
+	}
+
+	query := `EXEC sp_getapplock 
+	@Resource = @p1,
+	@LockOwner='Session',
+	@LockMode = 'Exclusive';`
+
+	if _, err := s.conn.ExecContext(ctx, query, aid); err != nil {
+		return fmt.Errorf("try lock failed: %w", err)
+	}
+
+	s.isLocked = true
+	return nil
+}
+
+// Unlock is the implementation of the unlock for explicit locking
+func (s *SQLServer) unlock(ctx context.Context) error {
+	if !s.isLocked {
+		return nil
+	}
+
+	aid, err := lock.Generate(s.DatabaseName, s.SchemaName)
+	if err != nil {
+		return err
+	}
+
+	query := `EXEC sp_releaseapplock  
+	@Resource = @p1, 
+	@LockOwner='Session';`
+
+	if _, err := s.conn.ExecContext(ctx, query, aid); err != nil {
+		return err
+	}
+	s.isLocked = false
+	return nil
+}
+
+func (s *SQLServer) ensureTable(ctx context.Context) (err error) {
+	if err = s.lock(ctx); err != nil {
+		return err
+	}
+
+	defer func() {
+		if e := s.unlock(ctx); e != nil {
+			if err == nil {
+				err = e
+			} else {
+				err = fmt.Errorf("failed to unlock table: %w", err)
+			}
+		}
+	}()
+
+	query := fmt.Sprintf(
+		`IF NOT EXISTS (SELECT * FROM sysobjects WHERE name='%[2]s' and xtype='U') CREATE TABLE %[1]s.%[2]s (
+	id int IDENTITY(1,1) NOT NULL PRIMARY KEY,
+	dispatched BIT NOT NULL DEFAULT 0,
+	dispatched_at DATETIME,
+	payload VARBINARY(MAX)  NOT NULL,
+	options VARBINARY(MAX),
+	headers VARBINARY(MAX)
+);
+`, s.SchemaName, s.EventStoreTable)
+
+	if _, err = s.conn.ExecContext(ctx, query); err != nil {
+		return err
+	}
+
+	return nil
+}

sqlserver/sqlserver_example_test.go

@@ -0,0 +1,28 @@
+package sqlserver_test
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"os"
+
+	"github.com/italolelis/outboxer/sqlserver"
+)
+
+func ExampleSQLServer() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	db, err := sql.Open("sqlserver", os.Getenv("DS_DSN"))
+	if err != nil {
+		fmt.Printf("failed to connect to SQLServer: %s", err)
+		return
+	}
+
+	ds, err := sqlserver.WithInstance(ctx, db)
+	if err != nil {
+		fmt.Printf("failed to setup the data store: %s", err)
+		return
+	}
+	defer ds.Close()
+}