User Log package for default logger

* Modify the default logger to it also logs Line Numbers
* Update README w/ logging instructions

README.md

@@ -30,12 +30,25 @@ Install the library:
 
     $ go get github.com/harlow/kinesis-connectors
 
-### Example S3 Pipeline
+### Logging
 
-The S3 Pipeline performs the following steps:
+Default logging is handled by Package log. An application can override the defualt package logging by
+changing it's `logger` variable:
 
-1. Pull records from Kinesis and buffer them untill the desired threshold is reached.
-2. Upload the records to an S3 bucket.
+```go
+connector.SetLogger(NewCustomLogger())
+```
+
+The customer logger must implement the [Logger interface][log_interface].
+
+[log_interface]: https://github.com/harlow/kinesis-connectors/blob/master/logger.go
+
+### Example Pipeline
+
+The S3 Connector Pipeline performs the following steps:
+
+1. Pull records from Kinesis and buffer them untill the desired threshold is met.
+2. Upload the batch of records to an S3 bucket.
 3. Set the current Shard checkpoint in Redis.
 
 The config vars are loaded done with [gcfg].

default_logger.go

@@ -1,21 +0,0 @@
-package connector
-
-import "log"
-
-// DefaultLogger is an implementation for std lib logger.
-type DefaultLogger struct{}
-
-// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
-func (l *DefaultLogger) Fatalf(format string, v ...interface{}) {
-	log.Fatalf(format, v...)
-}
-
-// Printf calls Output to print to the standard logger. Arguments are
-// handled in the manner of fmt.Printf.
-func (l *DefaultLogger) Printf(format string, v ...interface{}) {
-	log.Printf(format, v...)
-}
-
-// Make sure that there is a default logger instance initialized, so
-// that we don't end up with panics.
-var logger Logger = &DefaultLogger{}

logger.go

@@ -1,5 +1,10 @@
 package connector
 
+import (
+	"log"
+	"os"
+)
+
 // Logger sends pipeline info and errors to logging endpoint. The logger could be
 // used to send to STDOUT, Syslog, or any number of distributed log collecting platforms.
 type Logger interface {
@@ -7,6 +12,9 @@ type Logger interface {
 	Printf(format string, v ...interface{})
 }
 
+// specify a default logger so that we don't end up with panics.
+var logger Logger = log.New(os.Stdout, "", log.Ldate|log.Ltime|log.Lshortfile)
+
 // SetLogger adds the ability to change the logger so that external packages
 // can control the logging for this package
 func SetLogger(l Logger) {