Fix deadlock

README.md

@@ -41,14 +41,15 @@ with `sudo dpkg -i` and `sudo rpm -i` respectively.
 #### Current status
 
 - 🚧 Under development, expect bugs, errors, and unexpected crashes.
-- 🐞 Bug and error reports are very appreciated.
+- 🐞 Bug and error report very well appreciated.
 - 📣 I highly recommend to check for periodic updates.
 
 ##### Known Issues
 
 - ❗️Critically low amount of tests.
-- ❗️If you query a single connection a lot, it will result in an `Error 1040: To many connections`
-  error. [Working on a fix](https://github.com/KenanBek/dbui/tree/fix-deadlock).
+- ⚠️Having multiple connections and many queries triggers a high CPU load. Now
+  when [this PR](https://github.com/KenanBek/dbui/pull/28) merged, as a next step, I will work on profiling the
+  application.
 
 ## Demo
 

internal/dbui.go

@@ -1,5 +1,7 @@
 package internal
 
+import "log"
+
 //go:generate mockgen -source=dbui.go -destination=./controller/config_mock_test.go -package=controller -mock_names=AppConfig=MockAppConfig
 
 type (
@@ -54,4 +56,30 @@ type (
 		// Current returns currently selected data source.
 		Current() DataSource
 	}
+
+	// Closable is the interface that wraps Close method.
+	Closable interface {
+		Close() error
+	}
+
+	// Committable is the interface that wraps Commit method.
+	Committable interface {
+		Commit() error
+	}
 )
+
+// CloseOrLog tries to close and logs if it fails.
+func CloseOrLog(c Closable) {
+	err := c.Close()
+	if err != nil {
+		log.Printf("failed to close: %v\n", err)
+	}
+}
+
+// CommitOrLog tries to commit and logs if it fails.
+func CommitOrLog(c Committable) {
+	err := c.Commit()
+	if err != nil {
+		log.Printf("failed to commit: %v\n", err)
+	}
+}

internal/mysql/mysql.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	_ "github.com/go-sql-driver/mysql" // import mysql driver.
+	"github.com/kenanbek/dbui/internal"
 )
 
 // DataSource implements internal.DataSource interface for MySQL storage.
@@ -15,16 +16,19 @@ type DataSource struct {
 
 func (d *DataSource) query(schema, query string) (data [][]*string, err error) {
 	tx, err := d.db.Begin()
+	defer internal.CommitOrLog(tx)
 	if err != nil {
 		return
 	}
 
-	_, err = tx.Query(fmt.Sprintf("USE %s", schema))
+	res, err := tx.Query(fmt.Sprintf("USE %s", schema))
+	defer internal.CloseOrLog(res)
 	if err != nil {
 		return
 	}
 
 	rows, err := tx.Query(query)
+	defer internal.CloseOrLog(rows)
 	if err != nil {
 		return
 	}
@@ -83,6 +87,7 @@ func (d *DataSource) Ping() error {
 // ListSchemas exported.
 func (d *DataSource) ListSchemas() (schemas []string, err error) {
 	res, err := d.db.Query("SHOW DATABASES")
+	defer internal.CloseOrLog(res)
 	if err != nil {
 		return
 	}
@@ -102,24 +107,27 @@ func (d *DataSource) ListSchemas() (schemas []string, err error) {
 // ListTables exported.
 func (d *DataSource) ListTables(schema string) (tables []string, err error) {
 	tx, err := d.db.Begin()
+	defer internal.CommitOrLog(tx)
 	if err != nil {
 		return
 	}
 
-	_, err = tx.Query(fmt.Sprintf("USE %s", schema))
+	useRes, err := tx.Query(fmt.Sprintf("USE %s", schema))
+	defer internal.CloseOrLog(useRes)
 	if err != nil {
 		return
 	}
 
-	res, err := tx.Query("SHOW TABLES")
+	resShow, err := tx.Query("SHOW TABLES")
+	defer internal.CloseOrLog(resShow)
 	if err != nil {
 		return
 	}
 
 	tables = []string{}
-	for res.Next() {
+	for resShow.Next() {
 		var tableName string
-		err = res.Scan(&tableName)
+		err = resShow.Scan(&tableName)
 		if err == nil {
 			tables = append(tables, tableName)
 		}

internal/postgresql/postgresql.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/kenanbek/dbui/internal"
 	_ "github.com/lib/pq" // import pq driver for PostgreSQL.
 )
 
@@ -15,6 +16,7 @@ type DataSource struct {
 
 func (d *DataSource) query(query string) (data [][]*string, err error) {
 	rows, err := d.db.Query(query)
+	defer internal.CloseOrLog(rows)
 	if err != nil {
 		return
 	}
@@ -73,6 +75,7 @@ func (d *DataSource) Ping() error {
 // ListSchemas exported.
 func (d *DataSource) ListSchemas() (schemas []string, err error) {
 	res, err := d.db.Query("SELECT datname FROM pg_database WHERE datistemplate = false")
+	defer internal.CloseOrLog(res)
 	if err != nil {
 		return
 	}
@@ -93,6 +96,7 @@ func (d *DataSource) ListSchemas() (schemas []string, err error) {
 func (d *DataSource) ListTables(schema string) (tables []string, err error) {
 	queryStr := fmt.Sprintf("SELECT table_name FROM information_schema.tables t WHERE t.table_schema='public' AND t.table_type='BASE TABLE' AND t.table_catalog='%s' ORDER BY table_name;", schema)
 	res, err := d.db.Query(queryStr)
+	defer internal.CloseOrLog(res)
 	if err != nil {
 		return
 	}