maillog: Introduce a special-purpose mail logging package

The default INFO logs are more oriented towards debugging and can be
a bit too verbose when looking for high-level information.

This patch introduces a new "maillog" package, used to log messages of
particular relevance to mail transmission at a higher level.

internal/config/config.go

@@ -70,6 +70,10 @@ func Load(path string) (*Config, error) {
 		c.DropCharacters = "."
 	}
 
+	if c.MailLogPath == "" {
+		c.MailLogPath = "<syslog>"
+	}
+
 	return c, nil
 }
 
@@ -84,4 +88,5 @@ func LogConfig(c *Config) {
 	glog.Infof("  Data directory: %s", c.DataDir)
 	glog.Infof("  Suffix separators: %s", c.SuffixSeparators)
 	glog.Infof("  Drop characters: %s", c.DropCharacters)
+	glog.Infof("  Mail log: %s", c.MailLogPath)
 }

internal/config/config.pb.go

@@ -68,13 +68,19 @@ type Config struct {
 	// Suffix separator, to perform suffix removal of local users.
 	// For example, if you set this to "-+", email to local user
 	// "user-blah" and "user+blah" will be delivered to "user".
-	// Default: none.
+	// Including "+" is strongly encouraged, as it is assumed for email
+	// forwarding.
+	// Default: "+".
 	SuffixSeparators string `protobuf:"bytes,9,opt,name=suffix_separators,json=suffixSeparators" json:"suffix_separators,omitempty"`
 	// Characters to drop from the user part on local emails.
 	// For example, if you set this to "._", email to local user
 	// "u.se_r" will be delivered to "user".
-	// Default: none.
+	// Default: ".".
 	DropCharacters string `protobuf:"bytes,10,opt,name=drop_characters,json=dropCharacters" json:"drop_characters,omitempty"`
+	// Path where to write the mail log to.
+	// If "<syslog>", log using the syslog (at MAIL|INFO priority).
+	// Default: <syslog>
+	MailLogPath string `protobuf:"bytes,11,opt,name=mail_log_path,json=mailLogPath" json:"mail_log_path,omitempty"`
 }
 
 func (m *Config) Reset()                    { *m = Config{} }
@@ -89,24 +95,25 @@ func init() {
 func init() { proto.RegisterFile("config.proto", fileDescriptor0) }
 
 var fileDescriptor0 = []byte{
-	// 296 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x6c, 0x91, 0x41, 0x4e, 0xeb, 0x30,
-	0x10, 0x86, 0xd5, 0x97, 0x47, 0x9a, 0x9a, 0x02, 0xad, 0x05, 0xc2, 0xb0, 0x2a, 0x6c, 0x40, 0x42,
-	0xb0, 0x41, 0x88, 0x75, 0x68, 0xb6, 0x6c, 0xda, 0x03, 0x58, 0x4e, 0xec, 0xa4, 0x23, 0xd5, 0x76,
-	0x64, 0x1b, 0x54, 0xb8, 0x14, 0x57, 0x64, 0xe2, 0x42, 0x8a, 0x04, 0xcb, 0xf9, 0xfe, 0x6f, 0xec,
-	0xf1, 0x98, 0x8c, 0x2b, 0x6b, 0x6a, 0x68, 0xee, 0x5a, 0x67, 0x83, 0xbd, 0xfc, 0x48, 0x48, 0x3a,
-	0x8f, 0x80, 0x9e, 0x93, 0x6c, 0x65, 0x7d, 0x30, 0x42, 0x2b, 0x36, 0x98, 0x0d, 0xae, 0x47, 0x8b,
-	0xbe, 0xa6, 0x57, 0x64, 0xa2, 0xc5, 0x86, 0x4b, 0x11, 0x04, 0xf7, 0xf0, 0xae, 0xb8, 0x2e, 0xd9,
-	0x3f, 0x74, 0x92, 0xc5, 0x01, 0xf2, 0x02, 0xf1, 0x12, 0xe9, 0x73, 0x49, 0x2f, 0xc8, 0xd8, 0xeb,
-	0xd0, 0x72, 0x21, 0xa5, 0x53, 0xde, 0xb3, 0x64, 0x96, 0xe0, 0x41, 0xfb, 0x1d, 0xcb, 0xb7, 0x88,
-	0xde, 0x12, 0xea, 0x5f, 0x4a, 0x0d, 0xde, 0x83, 0x35, 0xbd, 0xf8, 0x3f, 0x8a, 0xd3, 0x5d, 0xf2,
-	0x43, 0xd7, 0xd6, 0x40, 0xb0, 0x0e, 0x4c, 0xd3, 0xeb, 0x7b, 0x71, 0xc0, 0xe9, 0x2e, 0xf9, 0xd6,
-	0x1f, 0xc8, 0xa9, 0x16, 0xb0, 0xe6, 0x52, 0xad, 0xe1, 0x55, 0xb9, 0x37, 0x2e, 0x1a, 0x65, 0x02,
-	0x2f, 0xc1, 0xb0, 0x34, 0xf6, 0x1c, 0x77, 0x71, 0xf1, 0x95, 0xe6, 0x5d, 0xf8, 0x04, 0x86, 0x3e,
-	0x12, 0xf6, 0x57, 0x9b, 0x70, 0x8d, 0x67, 0xc3, 0x38, 0xda, 0xc9, 0xaf, 0xbe, 0x1c, 0x43, 0x7a,
-	0x46, 0xb2, 0xb8, 0x15, 0x09, 0x8e, 0x65, 0xf1, 0x82, 0x61, 0x57, 0x17, 0xe0, 0xe8, 0x0d, 0xc1,
-	0xe7, 0xd4, 0x35, 0x6c, 0xb8, 0x57, 0xad, 0x70, 0x02, 0x07, 0xf5, 0x6c, 0x14, 0x9d, 0xc9, 0x36,
-	0x58, 0xf6, 0x1c, 0x37, 0x7c, 0x24, 0x9d, 0x6d, 0x79, 0xb5, 0x42, 0x52, 0x05, 0x85, 0x2a, 0x89,
-	0xea, 0x61, 0x87, 0xe7, 0x3d, 0x2d, 0xd3, 0xf8, 0x71, 0xf7, 0x9f, 0x01, 0x00, 0x00, 0xff, 0xff,
-	0xd1, 0x68, 0xa2, 0x22, 0xc8, 0x01, 0x00, 0x00,
+	// 317 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x6c, 0x91, 0xdf, 0x4e, 0xc2, 0x30,
+	0x14, 0xc6, 0x83, 0x53, 0xfe, 0x14, 0x50, 0x68, 0x34, 0x56, 0xaf, 0x90, 0x1b, 0x4d, 0x8c, 0xde,
+	0x18, 0xe3, 0x35, 0xc2, 0xa5, 0x26, 0x06, 0x1e, 0xa0, 0xe9, 0x58, 0x19, 0x27, 0x59, 0xdb, 0xa5,
+	0xad, 0x06, 0x7d, 0x4d, 0x5f, 0xc8, 0xb3, 0x83, 0x0e, 0x13, 0xbd, 0x3c, 0xbf, 0xef, 0x77, 0xb6,
+	0x6f, 0x67, 0xac, 0xb7, 0x74, 0x76, 0x05, 0xf9, 0x6d, 0xe9, 0x5d, 0x74, 0xe3, 0xcf, 0x84, 0x35,
+	0xa7, 0x04, 0xf8, 0x39, 0x6b, 0xaf, 0x5d, 0x88, 0x56, 0x19, 0x2d, 0x1a, 0xa3, 0xc6, 0x55, 0x67,
+	0x5e, 0xcf, 0xfc, 0x92, 0x0d, 0x8c, 0xda, 0xc8, 0x4c, 0x45, 0x25, 0x03, 0x7c, 0x68, 0x69, 0x52,
+	0xb1, 0x87, 0x4e, 0x32, 0xef, 0x23, 0x9f, 0x21, 0x5e, 0x20, 0x7d, 0x4e, 0xf9, 0x05, 0xeb, 0x05,
+	0x13, 0x4b, 0xa9, 0xb2, 0xcc, 0xeb, 0x10, 0x44, 0x32, 0x4a, 0xf0, 0x41, 0xdd, 0x8a, 0x4d, 0xb6,
+	0x88, 0xdf, 0x30, 0x1e, 0x5e, 0x53, 0x03, 0x21, 0x80, 0xb3, 0xb5, 0xb8, 0x4f, 0xe2, 0x70, 0x97,
+	0xfc, 0xd2, 0x8d, 0xb3, 0x10, 0x9d, 0x07, 0x9b, 0xd7, 0xfa, 0x01, 0x15, 0x1c, 0xee, 0x92, 0x1f,
+	0xfd, 0x9e, 0x9d, 0x1a, 0x05, 0x85, 0xcc, 0x74, 0x01, 0x6f, 0xda, 0xbf, 0x4b, 0x95, 0x6b, 0x1b,
+	0x65, 0x0a, 0x56, 0x34, 0x69, 0xe7, 0xb8, 0x8a, 0x67, 0xdf, 0xe9, 0xa4, 0x0a, 0x1f, 0xc1, 0xf2,
+	0x07, 0x26, 0xfe, 0x5b, 0x53, 0x3e, 0x0f, 0xa2, 0x45, 0xd5, 0x4e, 0xfe, 0xec, 0x4d, 0x30, 0xe4,
+	0x67, 0xac, 0x4d, 0x57, 0xc9, 0xc0, 0x8b, 0x36, 0xbd, 0xa0, 0x55, 0xcd, 0x33, 0xf0, 0xfc, 0x9a,
+	0xe1, 0xe7, 0xac, 0x56, 0xb0, 0x91, 0x41, 0x97, 0xca, 0x2b, 0x2c, 0x1a, 0x44, 0x87, 0x9c, 0xc1,
+	0x36, 0x58, 0xd4, 0x1c, 0x2f, 0x7c, 0x94, 0x79, 0x57, 0xca, 0xe5, 0x1a, 0xc9, 0x32, 0x6a, 0x54,
+	0x19, 0xa9, 0x87, 0x15, 0x9e, 0xd6, 0x94, 0x8f, 0x59, 0x9f, 0x9a, 0x16, 0x2e, 0x97, 0xa5, 0x8a,
+	0x6b, 0xd1, 0x25, 0xad, 0x5b, 0xc1, 0x27, 0x97, 0xbf, 0x20, 0x4a, 0x9b, 0xf4, 0x73, 0xef, 0xbe,
+	0x02, 0x00, 0x00, 0xff, 0xff, 0x04, 0x0f, 0xa4, 0xff, 0xec, 0x01, 0x00, 0x00,
 }

internal/config/config.proto

@@ -59,5 +59,10 @@ message Config {
 	// "u.se_r" will be delivered to "user".
 	// Default: ".".
 	string drop_characters = 10;
+
+	// Path where to write the mail log to.
+	// If "<syslog>", log using the syslog (at MAIL|INFO priority).
+	// Default: <syslog>
+	string mail_log_path = 11;
 }