examples: add example of multi-instance output plugin

This change also updates the out_gstdout example to have argument names
that match more accurately what is being passed in by fluent-bit.

Signed-off-by: Jason Keene <[email protected]>

Author: Warren Fernandes

examples/out_gstdout/out_gstdout.go

@@ -1,23 +1,24 @@
 package main
 
-import "github.com/fluent/fluent-bit-go/output"
 import (
+	"C"
 	"fmt"
 	"unsafe"
-	"C"
+
+	"github.com/fluent/fluent-bit-go/output"
 )
 
 //export FLBPluginRegister
-func FLBPluginRegister(ctx unsafe.Pointer) int {
-	return output.FLBPluginRegister(ctx, "gstdout", "Stdout GO!")
+func FLBPluginRegister(def unsafe.Pointer) int {
+	return output.FLBPluginRegister(def, "gstdout", "Stdout GO!")
 }
 
 //export FLBPluginInit
 // (fluentbit will call this)
-// ctx (context) pointer to fluentbit context (state/ c code)
-func FLBPluginInit(ctx unsafe.Pointer) int {
+// plugin (context) pointer to fluentbit context (state/ c code)
+func FLBPluginInit(plugin unsafe.Pointer) int {
 	// Example to retrieve an optional configuration parameter
-	param := output.FLBPluginConfigKey(ctx, "param")
+	param := output.FLBPluginConfigKey(plugin, "param")
 	fmt.Printf("[flb-go] plugin parameter = '%s'\n", param)
 	return output.FLB_OK
 }

examples/out_multiinstance/Makefile

@@ -0,0 +1,5 @@
+all:
+	go build -buildmode=c-shared -o out_multiinstance.so
+
+clean:
+	rm -rf *.so *.h *~

examples/out_multiinstance/README.md

@@ -0,0 +1,3 @@
+This example demonstrates using a plugin where there are multiple instances
+and `FLBPluginFlushCtx` is used to disambiguate multiple instances of the
+output plugin.

examples/out_multiinstance/out.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"C"
+	"log"
+	"unsafe"
+
+	"github.com/fluent/fluent-bit-go/output"
+)
+
+//export FLBPluginRegister
+func FLBPluginRegister(def unsafe.Pointer) int {
+	return output.FLBPluginRegister(def, "multiinstance", "Testing multiple instances.")
+}
+
+//export FLBPluginInit
+func FLBPluginInit(plugin unsafe.Pointer) int {
+	id := output.FLBPluginConfigKey(plugin, "id")
+	log.Printf("[multiinstance] id = %q", id)
+	// Set the context to point to any Go variable
+	output.FLBPluginSetContext(plugin, unsafe.Pointer(&id))
+	return output.FLB_OK
+}
+
+//export FLBPluginFlush
+func FLBPluginFlush(data unsafe.Pointer, length C.int, tag *C.char) int {
+	log.Print("Flush called for unknown instance")
+	return output.FLB_OK
+}
+
+//export FLBPluginFlushCtx
+func FLBPluginFlushCtx(ctx, data unsafe.Pointer, length C.int, tag *C.char) int {
+	// Cast context back into the original type for the Go variable
+	id := (*string)(ctx)
+	log.Printf("Flush called for id: %s", *id)
+
+	dec := output.NewDecoder(data, int(length))
+
+	for {
+		ret, _, _ := output.GetRecord(dec)
+		if ret != 0 {
+			break
+		}
+	}
+
+	return output.FLB_OK
+}
+
+//export FLBPluginExit
+func FLBPluginExit() int {
+	return output.FLB_OK
+}
+
+func main() {
+}