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datasource.go
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datasource.go
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package sqlds
import (
"context"
"database/sql"
"encoding/json"
"errors"
"fmt"
"net/http"
"sync"
"time"
"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"
)
const defaultKeySuffix = "default"
var (
ErrorMissingMultipleConnectionsConfig = errors.New("received connection arguments but the feature is not enabled")
ErrorMissingDBConnection = errors.New("unable to get default db connection")
// Deprecated: ErrorMissingMultipleConnectionsConfig should be used instead
MissingMultipleConnectionsConfig = ErrorMissingMultipleConnectionsConfig
// Deprecated: ErrorMissingDBConnection should be used instead
MissingDBConnection = ErrorMissingDBConnection
)
func defaultKey(datasourceUID string) string {
return fmt.Sprintf("%s-%s", datasourceUID, defaultKeySuffix)
}
func keyWithConnectionArgs(datasourceUID string, connArgs json.RawMessage) string {
return fmt.Sprintf("%s-%s", datasourceUID, string(connArgs))
}
type dbConnection struct {
db *sql.DB
settings backend.DataSourceInstanceSettings
}
type SQLDatasource struct {
Completable
dbConnections sync.Map
c Driver
driverSettings DriverSettings
backend.CallResourceHandler
CustomRoutes map[string]func(http.ResponseWriter, *http.Request)
// Enabling multiple connections may cause that concurrent connection limits
// are hit. The datasource enabling this should make sure connections are cached
// if necessary.
EnableMultipleConnections bool
}
func (ds *SQLDatasource) getDBConnection(key string) (dbConnection, bool) {
conn, ok := ds.dbConnections.Load(key)
if !ok {
return dbConnection{}, false
}
return conn.(dbConnection), true
}
func (ds *SQLDatasource) storeDBConnection(key string, dbConn dbConnection) {
ds.dbConnections.Store(key, dbConn)
}
func getDatasourceUID(settings backend.DataSourceInstanceSettings) string {
datasourceUID := settings.UID
// Grafana < 8.0 won't include the UID yet
if datasourceUID == "" {
datasourceUID = fmt.Sprintf("%d", settings.ID)
}
return datasourceUID
}
// NewDatasource creates a new `SQLDatasource`.
// It uses the provided settings argument to call the ds.Driver to connect to the SQL server
func (ds *SQLDatasource) NewDatasource(settings backend.DataSourceInstanceSettings) (instancemgmt.Instance, error) {
db, err := ds.c.Connect(settings, nil)
if err != nil {
return nil, err
}
key := defaultKey(getDatasourceUID(settings))
ds.storeDBConnection(key, dbConnection{db, settings})
mux := http.NewServeMux()
err = ds.registerRoutes(mux)
if err != nil {
return nil, err
}
ds.CallResourceHandler = httpadapter.New(mux)
ds.driverSettings = ds.c.Settings(settings)
return ds, nil
}
// NewDatasource initializes the Datasource wrapper and instance manager
func NewDatasource(c Driver) *SQLDatasource {
return &SQLDatasource{
c: c,
}
}
// Dispose cleans up datasource instance resources.
// Note: Called when testing and saving a datasource
func (ds *SQLDatasource) Dispose() {
}
// QueryData creates the Responses list and executes each query
func (ds *SQLDatasource) QueryData(ctx context.Context, req *backend.QueryDataRequest) (*backend.QueryDataResponse, error) {
var (
response = NewResponse(backend.NewQueryDataResponse())
wg = sync.WaitGroup{}
)
wg.Add(len(req.Queries))
// Execute each query and store the results by query RefID
for _, q := range req.Queries {
go func(query backend.DataQuery) {
frames, err := ds.handleQuery(ctx, query, getDatasourceUID(*req.PluginContext.DataSourceInstanceSettings))
response.Set(query.RefID, backend.DataResponse{
Frames: frames,
Error: err,
})
wg.Done()
}(q)
}
wg.Wait()
return response.Response(), nil
}
func (ds *SQLDatasource) GetDBFromQuery(q *Query, datasourceUID string) (*sql.DB, error) {
_, dbConn, err := ds.getDBConnectionFromQuery(q, datasourceUID)
return dbConn.db, err
}
func (ds *SQLDatasource) getDBConnectionFromQuery(q *Query, datasourceUID string) (string, dbConnection, error) {
if !ds.EnableMultipleConnections && len(q.ConnectionArgs) > 0 {
return "", dbConnection{}, MissingMultipleConnectionsConfig
}
// The database connection may vary depending on query arguments
// The raw arguments are used as key to store the db connection in memory so they can be reused
key := defaultKey(datasourceUID)
dbConn, ok := ds.getDBConnection(key)
if !ok {
return "", dbConnection{}, MissingDBConnection
}
if !ds.EnableMultipleConnections || len(q.ConnectionArgs) == 0 {
return key, dbConn, nil
}
key = keyWithConnectionArgs(datasourceUID, q.ConnectionArgs)
if cachedConn, ok := ds.getDBConnection(key); ok {
return key, cachedConn, nil
}
var err error
db, err := ds.c.Connect(dbConn.settings, q.ConnectionArgs)
if err != nil {
return "", dbConnection{}, err
}
// Assign this connection in the cache
dbConn = dbConnection{db, dbConn.settings}
ds.storeDBConnection(key, dbConn)
return key, dbConn, nil
}
// handleQuery will call query, and attempt to reconnect if the query failed
func (ds *SQLDatasource) handleQuery(ctx context.Context, req backend.DataQuery, datasourceUID string) (data.Frames, error) {
// Convert the backend.DataQuery into a Query object
q, err := GetQuery(req)
if err != nil {
return nil, err
}
// Apply supported macros to the query
q.RawSQL, err = Interpolate(ds.c, q)
if err != nil {
return getErrorFrameFromQuery(q), fmt.Errorf("%s: %w", "Could not apply macros", err)
}
// Apply the default FillMode, overwritting it if the query specifies it
fillMode := ds.driverSettings.FillMode
if q.FillMissing != nil {
fillMode = q.FillMissing
}
// Retrieve the database connection
cacheKey, dbConn, err := ds.getDBConnectionFromQuery(q, datasourceUID)
if err != nil {
return getErrorFrameFromQuery(q), err
}
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 := QueryDB(ctx, dbConn.db, ds.c.Converters(), fillMode, q)
if err == nil {
return res, nil
}
if errors.Is(err, ErrorNoResults) {
return res, nil
}
// If there's a query error that didn't exceed the
// context deadline retry the query
if errors.Is(err, ErrorQuery) && !errors.Is(err, context.DeadlineExceeded) {
for i := 0; i < ds.driverSettings.Retries; i++ {
backend.Logger.Warn(fmt.Sprintf("query failed. retrying %d times", i))
db, err := ds.dbReconnect(dbConn, q, cacheKey)
if err != nil {
return nil, err
}
if ds.driverSettings.Pause > 0 {
time.Sleep(time.Duration(ds.driverSettings.Pause * int(time.Second)))
}
res, err = QueryDB(ctx, db, ds.c.Converters(), fillMode, q)
if err == nil {
return res, err
}
}
}
// allow retries on timeouts
if errors.Is(err, context.DeadlineExceeded) {
for i := 0; i < ds.driverSettings.Retries; i++ {
backend.Logger.Warn(fmt.Sprintf("connection timed out. retrying %d times", i))
db, err := ds.dbReconnect(dbConn, q, cacheKey)
if err != nil {
continue
}
res, err = QueryDB(ctx, db, ds.c.Converters(), fillMode, q)
if err == nil {
return res, err
}
}
}
return nil, err
}
func (ds *SQLDatasource) dbReconnect(dbConn dbConnection, q *Query, cacheKey string) (*sql.DB, error) {
if err := dbConn.db.Close(); err != nil {
backend.Logger.Warn(fmt.Sprintf("closing existing connection failed: %s", err.Error()))
}
db, err := ds.c.Connect(dbConn.settings, q.ConnectionArgs)
if err != nil {
return nil, err
}
ds.storeDBConnection(cacheKey, dbConnection{db, dbConn.settings})
return db, nil
}
// CheckHealth pings the connected SQL database
func (ds *SQLDatasource) CheckHealth(ctx context.Context, req *backend.CheckHealthRequest) (*backend.CheckHealthResult, error) {
key := defaultKey(getDatasourceUID(*req.PluginContext.DataSourceInstanceSettings))
dbConn, ok := ds.getDBConnection(key)
if !ok {
return nil, MissingDBConnection
}
if ds.driverSettings.Retries == 0 {
return ds.check(dbConn)
}
return ds.checkWithRetries(dbConn)
}
func (ds *SQLDatasource) DriverSettings() DriverSettings {
return ds.driverSettings
}
func (ds *SQLDatasource) checkWithRetries(conn dbConnection) (*backend.CheckHealthResult, error) {
var result *backend.CheckHealthResult
var err error
for i := 0; i < ds.driverSettings.Retries; i++ {
result, err = ds.check(conn)
if err == nil {
return result, err
}
}
// TODO: failed health checks don't return an error
return result, nil
}
func (ds *SQLDatasource) check(conn dbConnection) (*backend.CheckHealthResult, error) {
if err := ds.ping(conn); err != nil {
return &backend.CheckHealthResult{
Status: backend.HealthStatusError,
Message: err.Error(),
}, err
}
return &backend.CheckHealthResult{
Status: backend.HealthStatusOk,
Message: "Data source is working",
}, nil
}
func (ds *SQLDatasource) ping(conn dbConnection) error {
if ds.driverSettings.Timeout == 0 {
return conn.db.Ping()
}
ctx, cancel := context.WithTimeout(context.Background(), ds.driverSettings.Timeout)
defer cancel()
return conn.db.PingContext(ctx)
}