More efficient logging with log levels

conn.go

@@ -34,6 +34,7 @@ type ConnConfig struct {
 	UseFallbackTLS    bool        // Try FallbackTLSConfig if connecting with TLSConfig fails. Used for preferring TLS, but allowing unencrypted, or vice-versa
 	FallbackTLSConfig *tls.Config // config for fallback TLS connection (only used if UseFallBackTLS is true)-- nil disables TLS
 	Logger            Logger
+	LogLevel          int
 	Dial              DialFunc
 }
 
@@ -56,6 +57,7 @@ type Conn struct {
 	alive              bool
 	causeOfDeath       error
 	logger             Logger
+	logLevel           int
 	mr                 msgReader
 	fp                 *fastpath
 	pgsql_af_inet      byte
@@ -111,10 +113,16 @@ func Connect(config ConnConfig) (c *Conn, err error) {
 	c = new(Conn)
 
 	c.config = config
-	if c.config.Logger != nil {
-		c.logger = c.config.Logger
+
+	if c.config.LogLevel != 0 {
+		c.logLevel = c.config.LogLevel
 	} else {
-		c.logger = dlogger
+		// Preserve pre-LogLevel behavior by defaulting to LogLevelDebug
+		c.logLevel = LogLevelDebug
+	}
+	c.logger = c.config.Logger
+	if c.logger == nil {
+		c.logLevel = LogLevelNone
 	}
 
 	if c.config.User == "" {
@@ -123,12 +131,16 @@ func Connect(config ConnConfig) (c *Conn, err error) {
 			return nil, err
 		}
 		c.config.User = user.Username
-		c.logger.Debug("Using default connection config", "User", c.config.User)
+		if c.logLevel >= LogLevelDebug {
+			c.logger.Debug("Using default connection config", "User", c.config.User)
+		}
 	}
 
 	if c.config.Port == 0 {
 		c.config.Port = 5432
-		c.logger.Debug("Using default connection config", "Port", c.config.Port)
+		if c.logLevel >= LogLevelDebug {
+			c.logger.Debug("Using default connection config", "Port", c.config.Port)
+		}
 	}
 
 	network := "tcp"
@@ -159,17 +171,23 @@ func Connect(config ConnConfig) (c *Conn, err error) {
 }
 
 func (c *Conn) connect(config ConnConfig, network, address string, tlsConfig *tls.Config) (err error) {
-	c.logger.Info(fmt.Sprintf("Dialing PostgreSQL server at %s address: %s", network, address))
+	if c.logLevel >= LogLevelInfo {
+		c.logger.Info(fmt.Sprintf("Dialing PostgreSQL server at %s address: %s", network, address))
+	}
 	c.conn, err = c.config.Dial(network, address)
 	if err != nil {
-		c.logger.Error(fmt.Sprintf("Connection failed: %v", err))
+		if c.logLevel >= LogLevelError {
+			c.logger.Error(fmt.Sprintf("Connection failed: %v", err))
+		}
 		return err
 	}
 	defer func() {
 		if c != nil && err != nil {
 			c.conn.Close()
 			c.alive = false
-			c.logger.Error(err.Error())
+			if c.logLevel >= LogLevelError {
+				c.logger.Error(err.Error())
+			}
 		}
 	}()
 
@@ -179,9 +197,13 @@ func (c *Conn) connect(config ConnConfig, network, address string, tlsConfig *tl
 	c.lastActivityTime = time.Now()
 
 	if tlsConfig != nil {
-		c.logger.Debug("Starting TLS handshake")
+		if c.logLevel >= LogLevelDebug {
+			c.logger.Debug("Starting TLS handshake")
+		}
 		if err := c.startTLS(tlsConfig); err != nil {
-			c.logger.Error(fmt.Sprintf("TLS failed: %v", err))
+			if c.logLevel >= LogLevelError {
+				c.logger.Error(fmt.Sprintf("TLS failed: %v", err))
+			}
 			return err
 		}
 	}
@@ -215,7 +237,7 @@ func (c *Conn) connect(config ConnConfig, network, address string, tlsConfig *tl
 			}
 		case readyForQuery:
 			c.rxReadyForQuery(r)
-			if c.logger != dlogger {
+			if c.logLevel >= LogLevelInfo {
 				c.logger = &connLogger{logger: c.logger, pid: c.Pid}
 				c.logger.Info("Connection established")
 			}
@@ -292,7 +314,9 @@ func (c *Conn) Close() (err error) {
 	_, err = c.conn.Write(wbuf.buf)
 
 	c.die(errors.New("Closed"))
-	c.logger.Info("Closed connection")
+	if c.logLevel >= LogLevelInfo {
+		c.logger.Info("Closed connection")
+	}
 	return err
 }
 
@@ -460,11 +484,13 @@ func configSSL(sslmode string, cc *ConnConfig) error {
 // Prepare creates a prepared statement with name and sql. sql can contain placeholders
 // for bound parameters. These placeholders are referenced positional as $1, $2, etc.
 func (c *Conn) Prepare(name, sql string) (ps *PreparedStatement, err error) {
-	defer func() {
-		if err != nil {
-			c.logger.Error(fmt.Sprintf("Prepare `%s` as `%s` failed: %v", name, sql, err))
-		}
-	}()
+	if c.logLevel >= LogLevelError {
+		defer func() {
+			if err != nil {
+				c.logger.Error(fmt.Sprintf("Prepare `%s` as `%s` failed: %v", name, sql, err))
+			}
+		}()
+	}
 
 	// parse
 	wbuf := newWriteBuf(c, 'P')
@@ -853,7 +879,7 @@ func (c *Conn) Exec(sql string, arguments ...interface{}) (commandTag CommandTag
 	startTime := time.Now()
 	c.lastActivityTime = startTime
 
-	if c.logger != dlogger {
+	if c.logLevel >= LogLevelError {
 		defer func() {
 			if err == nil {
 				endTime := time.Now()
@@ -929,7 +955,7 @@ func (c *Conn) rxMsg() (t byte, r *msgReader, err error) {
 
 	c.lastActivityTime = time.Now()
 
-	if c.logger != dlogger {
+	if c.logLevel >= LogLevelTrace {
 		c.logger.Debug("rxMsg", "Type", string(t), "Size", c.mr.msgBytesRemaining)
 	}
 

conn_pool.go

@@ -19,6 +19,7 @@ type ConnPool struct {
 	maxConnections       int
 	afterConnect         func(*Conn) error
 	logger               Logger
+	logLevel             int
 	closed               bool
 }
 
@@ -42,10 +43,16 @@ func NewConnPool(config ConnPoolConfig) (p *ConnPool, err error) {
 	}
 
 	p.afterConnect = config.AfterConnect
-	if config.Logger != nil {
-		p.logger = config.Logger
+
+	if config.LogLevel != 0 {
+		p.logLevel = config.LogLevel
 	} else {
-		p.logger = &discardLogger{}
+		// Preserve pre-LogLevel behavior by defaulting to LogLevelDebug
+		p.logLevel = LogLevelDebug
+	}
+	p.logger = config.Logger
+	if p.logger == nil {
+		p.logLevel = LogLevelNone
 	}
 
 	p.allConnections = make([]*Conn, 0, p.maxConnections)
@@ -92,7 +99,9 @@ func (p *ConnPool) Acquire() (c *Conn, err error) {
 
 	// All connections are in use and we cannot create more
 	if len(p.availableConnections) == 0 {
-		p.logger.Warn("All connections in pool are busy - waiting...")
+		if p.logLevel >= LogLevelWarn {
+			p.logger.Warn("All connections in pool are busy - waiting...")
+		}
 		for len(p.availableConnections) == 0 {
 			p.cond.Wait()
 		}

logger.go

@@ -5,6 +5,18 @@ import (
 	"fmt"
 )
 
+// The values for log levels are chosen such that the zero value means that no
+// log level was specified and we can default to LogLevelDebug to preserve
+// the behavior that existed prior to log level introduction.
+const (
+	LogLevelTrace = 6
+	LogLevelDebug = 5
+	LogLevelInfo  = 4
+	LogLevelWarn  = 3
+	LogLevelError = 2
+	LogLevelNone  = 1
+)
+
 // Logger is the interface used to get logging from pgx internals.
 // https://github.com/inconshreveable/log15 is the recommended logging package.
 // This logging interface was extracted from there. However, it should be simple
@@ -17,16 +29,6 @@ type Logger interface {
 	Error(msg string, ctx ...interface{})
 }
 
-type discardLogger struct{}
-
-// default discardLogger instance
-var dlogger = &discardLogger{}
-
-func (l *discardLogger) Debug(msg string, ctx ...interface{}) {}
-func (l *discardLogger) Info(msg string, ctx ...interface{})  {}
-func (l *discardLogger) Warn(msg string, ctx ...interface{})  {}
-func (l *discardLogger) Error(msg string, ctx ...interface{}) {}
-
 type connLogger struct {
 	logger Logger
 	pid    int32

query.go

@@ -52,6 +52,7 @@ type Rows struct {
 	sql       string
 	args      []interface{}
 	logger    Logger
+	logLevel  int
 }
 
 func (rows *Rows) FieldDescriptions() []FieldDescription {
@@ -70,14 +71,12 @@ func (rows *Rows) close() {
 
 	rows.closed = true
 
-	if rows.logger == dlogger {
-		return
-	}
-
 	if rows.err == nil {
-		endTime := time.Now()
-		rows.logger.Info("Query", "sql", rows.sql, "args", logQueryArgs(rows.args), "time", endTime.Sub(rows.startTime), "rowCount", rows.rowCount)
-	} else {
+		if rows.logLevel >= LogLevelInfo {
+			endTime := time.Now()
+			rows.logger.Info("Query", "sql", rows.sql, "args", logQueryArgs(rows.args), "time", endTime.Sub(rows.startTime), "rowCount", rows.rowCount)
+		}
+	} else if rows.logLevel >= LogLevelError {
 		rows.logger.Error("Query", "sql", rows.sql, "args", logQueryArgs(rows.args))
 	}
 }
@@ -420,7 +419,7 @@ func (rows *Rows) Values() ([]interface{}, error) {
 // from Query and handle it in *Rows.
 func (c *Conn) Query(sql string, args ...interface{}) (*Rows, error) {
 	c.lastActivityTime = time.Now()
-	rows := &Rows{conn: c, startTime: c.lastActivityTime, sql: sql, args: args, logger: c.logger}
+	rows := &Rows{conn: c, startTime: c.lastActivityTime, sql: sql, args: args, logger: c.logger, logLevel: c.logLevel}
 
 	ps, ok := c.preparedStatements[sql]
 	if !ok {