Add new "--plaintext-metadata" flag.

When this flag is used, we don't templatize metadata JSON object for
every single request and json load it, but we only do that once and
re-use cached version for subsequent requests.

This results in much less overhead when metadata template functionality
is not needed and utilizing large metadata objects.

README.md

@@ -86,6 +86,7 @@ Flags:
   -B, --binary-file=           File path for the call data as serialized binary message or multiple count-prefixed messages.
   -m, --metadata=              Request metadata as stringified JSON. Either as an object or an array of objects.
   -M, --metadata-file=         File path for call metadata JSON file. Examples: /home/user/metadata.json or ./metadata.json.
+      --plaintext-metadata     True to not try to templatize the metadata object. This should be used when using large metadata obejects when template functionality is not used since it speeds things up.
       --stream-interval=0      Interval for stream requests between message sends.
       --reflect-metadata=      Reflect metadata as stringified JSON used only for reflection request.
   -o, --output=                Output path. If none provided stdout is used.

cmd/ghz/main.go

@@ -130,6 +130,10 @@ var (
 	mdPath      = kingpin.Flag("metadata-file", "File path for call metadata JSON file. Examples: /home/user/metadata.json or ./metadata.json.").
 			Short('M').PlaceHolder(" ").IsSetByUser(&isMDPathSet).String()
 
+	isPlainTextMetadataSet = false
+	plaintextMetadata      = kingpin.Flag("plaintext-metadata", "Don't try to templatize metadata string for each request and used cached value for all the requests.").
+				Default("false").IsSetByUser(&isPlainTextMetadataSet).Bool()
+
 	isSISet = false
 	si      = kingpin.Flag("stream-interval", "Interval for stream requests between message sends.").
 		Default("0").IsSetByUser(&isSISet).Duration()
@@ -394,6 +398,7 @@ func createConfigFromArgs(cfg *runner.Config) error {
 	cfg.BinDataPath = *binPath
 	cfg.Metadata = metadataArray
 	cfg.MetadataPath = *mdPath
+	cfg.PlaintextMetadata = *plaintextMetadata
 	cfg.SI = runner.Duration(*si)
 	cfg.Output = *output
 	cfg.Format = *format
@@ -512,6 +517,10 @@ func mergeConfig(dest *runner.Config, src *runner.Config) error {
 		dest.MetadataPath = src.MetadataPath
 	}
 
+	if isPlainTextMetadataSet {
+		dest.PlaintextMetadata = src.PlaintextMetadata
+	}
+
 	if isSISet {
 		dest.SI = src.SI
 	}

runner/config.go

@@ -82,6 +82,7 @@ type Config struct {
 	BinDataPath       string            `json:"binary-file" toml:"binary-file" yaml:"binary-file"`
 	Metadata          interface{}       `json:"metadata,omitempty" toml:"metadata,omitempty" yaml:"metadata,omitempty"`
 	MetadataPath      string            `json:"metadata-file" toml:"metadata-file" yaml:"metadata-file"`
+	PlaintextMetadata bool              `json:"plaintextMetadata" toml:"plaintextMetadata" yaml:"PlaintextMetadata"`
 	SI                Duration          `json:"stream-interval" toml:"stream-interval" yaml:"stream-interval"`
 	Output            string            `json:"output" toml:"output" yaml:"output"`
 	Format            string            `json:"format" toml:"format" yaml:"format" default:"summary"`

runner/options.go

@@ -58,10 +58,11 @@ type RunConfig struct {
 	streamInterval time.Duration
 
 	// data
-	data     []byte
-	binary   bool
-	metadata []byte
-	rmd      map[string]string
+	data              []byte
+	binary            bool
+	metadata          []byte
+	PlaintextMetadata bool
+	rmd               map[string]string
 
 	// debug
 	hasLog bool
@@ -435,6 +436,15 @@ func WithMetadataFromFile(path string) Option {
 	}
 }
 
+// WithPlaintextMetadata to not utilize metadata templating functionality
+func WithPlaintextMetadata(value bool) Option {
+	return func(o *RunConfig) error {
+		o.PlaintextMetadata = value
+
+		return nil
+	}
+}
+
 // WithName sets the name of the test run
 //	WithName("greeter service test")
 func WithName(name string) Option {
@@ -725,6 +735,7 @@ func fromConfig(cfg *Config) []Option {
 		WithName(cfg.Name),
 		WithCPUs(cfg.CPUs),
 		WithMetadata(cfg.Metadata),
+		WithPlaintextMetadata(cfg.PlaintextMetadata),
 		WithTags(cfg.Tags),
 		WithStreamInterval(time.Duration(cfg.SI)),
 		WithReflectionMetadata(cfg.ReflectMetadata),

runner/worker.go

@@ -32,6 +32,10 @@ type Worker struct {
 	// cached messages only for binary
 	cachedMessages []*dynamic.Message
 
+	// cached metadata array for situations where metadata templating
+	// functionality is not used
+	cachedReqMDs []metadata.MD
+
 	// non-binary json optimization
 	arrayJSONData []string
 }
@@ -82,19 +86,28 @@ func (w *Worker) makeRequest() error {
 		}
 	}
 
-	mdArray, err := ctd.executeMetadataArray(string(w.config.metadata))
-	if err != nil {
-		return err
-	}
-
 	var reqMDs []metadata.MD
 
-	if len(mdArray) > 0 {
-		for _, mdItem := range mdArray {
-			reqMDs = append(reqMDs, metadata.New(mdItem))
-		}
+	if w.cachedReqMDs != nil {
+		// If templating is not used and cached metadata is available, we use this
+		// array. This way we avoid rendering and json loading potentially very
+		// large metadata object for every single request
+		reqMDs = w.cachedReqMDs
 	} else {
-		reqMDs = append(reqMDs, metadata.MD{})
+		mdArray, err := ctd.executeMetadataArray(string(w.config.metadata))
+		if err != nil {
+			return err
+		}
+
+		if len(mdArray) > 0 {
+			for _, mdItem := range mdArray {
+				reqMDs = append(reqMDs, metadata.New(mdItem))
+			}
+		} else {
+			reqMDs = append(reqMDs, metadata.MD{})
+		}
+
+		w.cachedReqMDs = reqMDs
 	}
 
 	metadatasLen := len(reqMDs)

www/docs/examples.md

@@ -95,9 +95,16 @@ ghz --insecure \
   --call helloworld.Greeter.SayHello \
   -d '[{"name":"Joe"},{"name":"Bob"}]' \
   -m '[{"item one":"value 1"},{"item two":"value 2"}]' \
+  --plaintext-metadata \
   0.0.0.0:50051
 ```
 
+If you are using large metadata array and don't rely on template functionality in metadata
+JSON string, you should also use ``--plaintext-metadata`` as shown above.
+
+This will cause the code to skip rendering the metadata item as a template for every single
+RPC request and will speed things up.
+
 <a name="custom-parameters">
 ### Custom parameters