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Merged
madelynnblue merged 1 commit into from
May 3, 2020
Merged

Add NotificationConnector and methods #966

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46 changes: 46 additions & 0 deletions notify.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ package pq
// This module contains support for Postgres LISTEN/NOTIFY.

import (
"context"
"database/sql/driver"
"errors"
"fmt"
Expand Down Expand Up @@ -40,6 +41,51 @@ func SetNotificationHandler(c driver.Conn, handler func(*Notification)) {
c.(*conn).notificationHandler = handler
}

// NotificationHandlerConnector wraps a regular connector and sets a notification handler
// on it.
type NotificationHandlerConnector struct {
driver.Connector
notificationHandler func(*Notification)
}

// Connect calls the underlying connector's connect method and then sets the
// notification handler.
func (n *NotificationHandlerConnector) Connect(ctx context.Context) (driver.Conn, error) {
c, err := n.Connector.Connect(ctx)
if err == nil {
SetNotificationHandler(c, n.notificationHandler)
}
return c, err
}

// ConnectorNotificationHandler returns the currently set notification handler, if any. If
// the given connector is not a result of ConnectorWithNotificationHandler, nil is
// returned.
func ConnectorNotificationHandler(c driver.Connector) func(*Notification) {
if c, ok := c.(*NotificationHandlerConnector); ok {
return c.notificationHandler
}
return nil
}

// ConnectorWithNotificationHandler creates or sets the given handler for the given
// connector. If the given connector is a result of calling this function
// previously, it is simply set on the given connector and returned. Otherwise,
// this returns a new connector wrapping the given one and setting the notification
// handler. A nil notification handler may be used to unset it.
//
// The returned connector is intended to be used with database/sql.OpenDB.
//
// Note: Notification handlers are executed synchronously by pq meaning commands
// won't continue to be processed until the handler returns.
func ConnectorWithNotificationHandler(c driver.Connector, handler func(*Notification)) *NotificationHandlerConnector {
if c, ok := c.(*NotificationHandlerConnector); ok {
c.notificationHandler = handler
return c
}
return &NotificationHandlerConnector{Connector: c, notificationHandler: handler}
}

const (
connStateIdle int32 = iota
connStateExpectResponse
Expand Down
42 changes: 42 additions & 0 deletions notify_test.go
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
package pq

import (
"database/sql"
"database/sql/driver"
"errors"
"fmt"
"io"
Expand Down Expand Up @@ -568,3 +570,43 @@ func TestListenerPing(t *testing.T) {
t.Fatalf("expected errListenerClosed; got %v", err)
}
}

func TestConnectorWithNotificationHandler_Simple(t *testing.T) {
b, err := NewConnector("")
if err != nil {
t.Fatal(err)
}
var notification *Notification
// Make connector w/ handler to set the local var
c := ConnectorWithNotificationHandler(b, func(n *Notification) { notification = n })
sendNotification(c, t, "Test notification #1")
if notification == nil || notification.Extra != "Test notification #1" {
t.Fatalf("Expected notification w/ message, got %v", notification)
}
// Unset the handler on the same connector
prevC := c
if c = ConnectorWithNotificationHandler(c, nil); c != prevC {
t.Fatalf("Expected to not create new connector but did")
}
sendNotification(c, t, "Test notification #2")
if notification == nil || notification.Extra != "Test notification #1" {
t.Fatalf("Expected notification to not change, got %v", notification)
}
// Set it back on the same connector
if c = ConnectorWithNotificationHandler(c, func(n *Notification) { notification = n }); c != prevC {
t.Fatal("Expected to not create new connector but did")
}
sendNotification(c, t, "Test notification #3")
if notification == nil || notification.Extra != "Test notification #3" {
t.Fatalf("Expected notification w/ message, got %v", notification)
}
}

func sendNotification(c driver.Connector, t *testing.T, escapedNotification string) {
db := sql.OpenDB(c)
defer db.Close()
sql := fmt.Sprintf("LISTEN foo; NOTIFY foo, '%s';", escapedNotification)
if _, err := db.Exec(sql); err != nil {
t.Fatal(err)
}
}