Merge pull request #32 from grafana/use-context

Bug fixes / context refactor

Author: kminehart

completion.go

@@ -3,13 +3,16 @@ package sqlds
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
-	"github.com/pkg/errors"
 )
 
+// ErrorNotImplemented is returned if the function is not implemented by the provided Driver (the Completable pointer is nil)
+var ErrorNotImplemented = errors.New("not implemented")
+
 // Completable will be used to autocomplete Tables Schemas and Columns for SQL languages
 type Completable interface {
 	Schemas(ctx context.Context) ([]string, error)
@@ -43,7 +46,7 @@ type columnRequest struct {
 
 func (ds *sqldatasource) getSchemas(rw http.ResponseWriter, req *http.Request) {
 	if ds.Completable == nil {
-		handleError(rw, errors.New("not implemented"))
+		handleError(rw, ErrorNotImplemented)
 		return
 	}
 
@@ -58,7 +61,7 @@ func (ds *sqldatasource) getSchemas(rw http.ResponseWriter, req *http.Request) {
 
 func (ds *sqldatasource) getTables(rw http.ResponseWriter, req *http.Request) {
 	if ds.Completable == nil {
-		handleError(rw, errors.New("not implemented"))
+		handleError(rw, ErrorNotImplemented)
 		return
 	}
 
@@ -78,7 +81,7 @@ func (ds *sqldatasource) getTables(rw http.ResponseWriter, req *http.Request) {
 
 func (ds *sqldatasource) getColumns(rw http.ResponseWriter, req *http.Request) {
 	if ds.Completable == nil {
-		handleError(rw, errors.New("not implemented"))
+		handleError(rw, ErrorNotImplemented)
 		return
 	}
 

datasource.go

@@ -3,23 +3,27 @@ package sqlds
 import (
 	"context"
 	"database/sql"
+	"errors"
+	"fmt"
 	"net/http"
 	"sync"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/backend/instancemgmt"
 	"github.com/grafana/grafana-plugin-sdk-go/backend/resource/httpadapter"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
-	"github.com/pkg/errors"
 )
 
 type sqldatasource struct {
-	db       *sql.DB
-	c        Driver
-	settings backend.DataSourceInstanceSettings
+	Completable
+
+	db *sql.DB
+	c  Driver
+
+	driverSettings DriverSettings
+	settings       backend.DataSourceInstanceSettings
 
 	backend.CallResourceHandler
-	Completable
 	CustomRoutes map[string]func(http.ResponseWriter, *http.Request)
 }
 
@@ -37,7 +41,9 @@ func (ds *sqldatasource) NewDatasource(settings backend.DataSourceInstanceSettin
 	if err != nil {
 		return nil, err
 	}
+
 	ds.CallResourceHandler = httpadapter.New(mux)
+	ds.driverSettings = ds.c.Settings(settings)
 
 	return ds, nil
 }
@@ -66,7 +72,7 @@ func (ds *sqldatasource) QueryData(ctx context.Context, req *backend.QueryDataRe
 	// Execute each query and store the results by query RefID
 	for _, q := range req.Queries {
 		go func(query backend.DataQuery) {
-			frames, err := ds.handleQuery(query)
+			frames, err := ds.handleQuery(ctx, query)
 
 			response.Set(query.RefID, backend.DataResponse{
 				Frames: frames,
@@ -83,7 +89,7 @@ func (ds *sqldatasource) QueryData(ctx context.Context, req *backend.QueryDataRe
 }
 
 // handleQuery will call query, and attempt to reconnect if the query failed
-func (ds *sqldatasource) handleQuery(req backend.DataQuery) (data.Frames, error) {
+func (ds *sqldatasource) handleQuery(ctx context.Context, req backend.DataQuery) (data.Frames, error) {
 	// Convert the backend.DataQuery into a Query object
 	q, err := GetQuery(req)
 	if err != nil {
@@ -93,30 +99,42 @@ func (ds *sqldatasource) handleQuery(req backend.DataQuery) (data.Frames, error)
 	// Apply supported macros to the query
 	q.RawSQL, err = interpolate(ds.c, q)
 	if err != nil {
-		return nil, errors.WithMessage(err, "Could not apply macros")
+		return nil, fmt.Errorf("%s: %w", "Could not apply macros", err)
 	}
 
 	// Apply the default FillMode, overwritting it if the query specifies it
-	fillMode := ds.c.FillMode()
+	fillMode := ds.driverSettings.FillMode
 	if q.FillMissing != nil {
 		fillMode = q.FillMissing
 	}
 
+	if ds.driverSettings.Timeout != 0 {
+		tctx, cancel := context.WithTimeout(ctx, ds.driverSettings.Timeout)
+		defer cancel()
+
+		ctx = tctx
+	}
+
 	// FIXES:
 	//  * Some datasources (snowflake) expire connections or have an authentication token that expires if not used in 1 or 4 hours.
 	//    Because the datasource driver does not include an option for permanent connections, we retry the connection
 	//    if the query fails. NOTE: this does not include some errors like "ErrNoRows"
-	res, err := query(ds.db, ds.c.Converters(), fillMode, q)
+	res, err := query(ctx, ds.db, ds.c.Converters(), fillMode, q)
 	if err == nil {
 		return res, nil
 	}
 
-	if errors.Cause(err) == ErrorQuery {
+	if errors.Is(err, ErrorNoResults) {
+		return res, nil
+	}
+
+	if errors.Is(err, ErrorQuery) {
 		ds.db, err = ds.c.Connect(ds.settings)
 		if err != nil {
 			return nil, err
 		}
-		return query(ds.db, ds.c.Converters(), fillMode, q)
+
+		return query(ctx, ds.db, ds.c.Converters(), fillMode, q)
 	}
 
 	return nil, err

driver.go

@@ -2,18 +2,25 @@ package sqlds
 
 import (
 	"database/sql"
+	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana-plugin-sdk-go/data/sqlutil"
 )
 
+type DriverSettings struct {
+	Timeout  time.Duration
+	FillMode *data.FillMissing
+}
+
 // Driver is a simple interface that defines how to connect to a backend SQL datasource
 // Plugin creators will need to implement this in order to create a managed datasource
 type Driver interface {
 	// Connect connects to the database. It does not need to call `db.Ping()`
 	Connect(backend.DataSourceInstanceSettings) (*sql.DB, error)
-	FillMode() *data.FillMissing
+	// Settings are read whenever the plugin is initialized, or after the data source settings are updated
+	Settings(backend.DataSourceInstanceSettings) DriverSettings
 	Macros() Macros
 	Converters() []sqlutil.Converter
 }

errors.go

@@ -1,12 +1,16 @@
 package sqlds
 
-import "github.com/pkg/errors"
+import "errors"
 
 var (
-	// ErrorBadDatasource ...
+	// ErrorBadDatasource is returned if the data source could not be asserted to the correct type (this should basically never happen?)
 	ErrorBadDatasource = errors.New("type assertion to datasource failed")
 	// ErrorJSON is returned when json.Unmarshal fails
 	ErrorJSON = errors.New("error unmarshaling query JSON the Query Model")
 	// ErrorQuery is returned when the query could not complete / execute
 	ErrorQuery = errors.New("error querying the database")
+	// ErrorTimeout is returned if the query has timed out
+	ErrorTimeout = errors.New("query timeout exceeded")
+	// ErrorNoResults is returned if there were no results returned
+	ErrorNoResults = errors.New("no results returned from query")
 )

go.mod

@@ -4,6 +4,5 @@ go 1.15
 
 require (
 	github.com/grafana/grafana-plugin-sdk-go v0.94.0
-	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.7.0
 )

go.sum

@@ -251,7 +251,6 @@ github.com/pierrec/lz4 v1.0.2-0.20190131084431-473cd7ce01a1/go.mod h1:3/3N9NVKO0
 github.com/pierrec/lz4 v2.0.5+incompatible/go.mod h1:pdkljMzZIN41W+lC3N2tnIh5sFi+IEE17M5jbnwPHcY=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/profile v1.2.1/go.mod h1:hJw3o1OdXxsrSjjVksARp5W95eeEaEfptyVZyv6JUPA=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

macros.go

@@ -1,11 +1,10 @@
 package sqlds
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"strings"
-
-	"github.com/pkg/errors"
 )
 
 var (

macros_test.go

@@ -4,9 +4,9 @@ import (
 	"database/sql"
 	"fmt"
 	"testing"
+	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
-	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana-plugin-sdk-go/data/sqlutil"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -17,12 +17,15 @@ type MockDB struct{}
 func (h *MockDB) Connect(backend.DataSourceInstanceSettings) (db *sql.DB, err error) {
 	return
 }
-func (h *MockDB) FillMode() (mode *data.FillMissing) {
+
+func (h *MockDB) Settings(backend.DataSourceInstanceSettings) (settings DriverSettings) {
 	return
 }
+
 func (h *MockDB) Converters() (sc []sqlutil.Converter) {
 	return
 }
+
 func (h *MockDB) Macros() (macros Macros) {
 	return map[string]MacroFunc{
 		"foo": func(query *Query, args []string) (out string, err error) {
@@ -37,6 +40,10 @@ func (h *MockDB) Macros() (macros Macros) {
 	}
 }
 
+func (h *MockDB) Timeout(backend.DataSourceInstanceSettings) time.Duration {
+	return time.Minute
+}
+
 func TestInterpolate(t *testing.T) {
 	type test struct {
 		name   string

query.go

@@ -1,14 +1,15 @@
 package sqlds
 
 import (
+	"context"
 	"database/sql"
 	"encoding/json"
+	"fmt"
 	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana-plugin-sdk-go/data/sqlutil"
-	"github.com/pkg/errors"
 )
 
 // FormatQueryOption defines how the user has chosen to represent the data
@@ -91,21 +92,21 @@ func getErrorFrameFromQuery(query *Query) data.Frames {
 }
 
 // query sends the query to the sql.DB and converts the rows to a dataframe.
-func query(db *sql.DB, converters []sqlutil.Converter, fillMode *data.FillMissing, query *Query) (data.Frames, error) {
+func query(ctx context.Context, db *sql.DB, converters []sqlutil.Converter, fillMode *data.FillMissing, query *Query) (data.Frames, error) {
 	// Query the rows from the database
-	rows, err := db.Query(query.RawSQL)
+	rows, err := db.QueryContext(ctx, query.RawSQL)
 	if err != nil {
-		return getErrorFrameFromQuery(query), errors.Wrap(ErrorQuery, err.Error())
+		return getErrorFrameFromQuery(query), fmt.Errorf("%w: %s", ErrorQuery, err.Error())
 	}
 
 	// Check for an error response
 	if err := rows.Err(); err != nil {
 		if err == sql.ErrNoRows {
 			// Should we even response with an error here?
 			// The panel will simply show "no data"
-			return getErrorFrameFromQuery(query), errors.WithMessage(err, "No results from query")
+			return getErrorFrameFromQuery(query), fmt.Errorf("%s: %w", "No results from query", err)
 		}
-		return getErrorFrameFromQuery(query), errors.WithMessage(err, "Error response from database")
+		return getErrorFrameFromQuery(query), fmt.Errorf("%s: %w", "Error response from database", err)
 	}
 
 	defer func() {
@@ -117,7 +118,7 @@ func query(db *sql.DB, converters []sqlutil.Converter, fillMode *data.FillMissin
 	// Convert the response to frames
 	res, err := getFrames(rows, -1, converters, fillMode, query)
 	if err != nil {
-		return nil, errors.WithMessage(err, "Could not process SQL results")
+		return getErrorFrameFromQuery(query), fmt.Errorf("%w: %s", err, "Could not process SQL results")
 	}
 
 	return res, nil
@@ -139,6 +140,16 @@ func getFrames(rows *sql.Rows, limit int64, converters []sqlutil.Converter, fill
 		return data.Frames{frame}, nil
 	}
 
+	count, err := frame.RowLen()
+
+	if err != nil {
+		return nil, err
+	}
+
+	if count == 0 {
+		return nil, ErrorNoResults
+	}
+
 	if frame.TimeSeriesSchema().Type == data.TimeSeriesTypeLong {
 		frame, err := data.LongToWide(frame, fillMode)
 		if err != nil {