Make inputsource generic taking bufio.SplitFunc as input

[vjsamuel]

This PR makes it a responsibility of the consumer of TCP inputsource to create the bufio.SplitFunc. Hence, there line_delimiter parameter is removed from inputsource and is moved to the input itself.

This allows input implementations to define more custom splitters.

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[houndci-bot]

exported function SplitFunc should have comment or be unexported

[ph]

@vjsamuel Instead of having two Config and two unpack can we use the same strategy as the TCP input and use [type embedding](https://github.com/elastic/beats/pull/7746/files#diff-8dbe6c5e5fa8f03003f5226255a1d1e8L31?

[ph]

@vjsamuel

The following will work and will be backward compatible with the existing configuration.
The struct structure can be different from the YML structure when you are using ucfg 'inline' option, also I've removed the check for the tcp.SplitFunc because we have a nonzero validation the factory cannot return NIL.

diff --git a/filebeat/input/syslog/config.go b/filebeat/input/syslog/config.go
index 4b90223f4..dd9f99b88 100644
--- a/filebeat/input/syslog/config.go
+++ b/filebeat/input/syslog/config.go
@@ -41,9 +41,17 @@ var defaultConfig = config{
 	},
 }
 
-var defaultTCP = tcp.Config{
-	Timeout:        time.Minute * 5,
-	MaxMessageSize: 20 * humanize.MiByte,
+type syslogTCP struct {
+	tcp.Config    `config:",inline"`
+	LineDelimiter string `config:"line_delimiter" validate:"nonzero"`
+}
+
+var defaultTCP = syslogTCP{
+	Config: tcp.Config{
+		Timeout:        time.Minute * 5,
+		MaxMessageSize: 20 * humanize.MiByte,
+	},
+	LineDelimiter: "\n",
 }
 
 var defaultUDP = udp.Config{
@@ -51,14 +59,6 @@ var defaultUDP = udp.Config{
 	Timeout:        time.Minute * 5,
 }
 
-type delimiterConf struct {
-	LineDelimiter string `config:"line_delimiter" validate:"nonzero"`
-}
-
-var defaultDelimiter = delimiterConf{
-	LineDelimiter: "\n",
-}
-
 func factory(
 	cb inputsource.NetworkFunc,
 	config common.ConfigNamespace,
@@ -72,16 +72,9 @@ func factory(
 			return nil, err
 		}
 
-		dConfig := defaultDelimiter
-		if err := cfg.Unpack(&dConfig); err != nil {
-			return nil, err
-		}
+		splitFunc := tcp.SplitFunc([]byte(config.LineDelimiter))
 
-		splitFunc := tcp.SplitFunc([]byte(dConfig.LineDelimiter))
-		if splitFunc != nil {
-			return nil, fmt.Errorf("error creating splitFunc from delimiter %s", dConfig.LineDelimiter)
-		}
-		return tcp.New(&config, splitFunc, cb)
+		return tcp.New(&config.Config, splitFunc, cb)
 	case udp.Name:
 		config := defaultUDP
 		if err := cfg.Unpack(&config); err != nil {
diff --git a/filebeat/input/tcp/input.go b/filebeat/input/tcp/input.go
index 1688af3c4..38eafb4ce 100644
--- a/filebeat/input/tcp/input.go
+++ b/filebeat/input/tcp/input.go
@@ -18,7 +18,6 @@
 package tcp
 
 import (
-	"fmt"
 	"sync"
 	"time"
 
@@ -78,9 +77,6 @@ func NewInput(
 	}
 
 	splitFunc := tcp.SplitFunc([]byte(config.LineDelimiter))
-	if splitFunc == nil {
-		return nil, fmt.Errorf("unable to create splitFunc for delimiter %s", config.LineDelimiter)
-	}
 
 	server, err := tcp.New(&config.Config, splitFunc, cb)
 	if err != nil {

[ph]

Jenkins test this please

[ph]

Only minor comment concerning type embedding.

[ph]

@vjsamuel I think something went wrong with the rebase?

[ph]

Small problem with the changelog.asciidoc

[ph]

Jenkins test this please

[ph]

WFG

[ph]

@vjsamuel There is some system test failing for the syslog tcp can you take a look?

[vjsamuel]

done

[ph]

Jenkins test this please