Adding Concurrency in Pool Manager (#1698)

Concurrency in the pool manager allows specializing pods concurrently based on a specified limit. 

Co-authored-by: Vishal <vishal-biyani@users.noreply.github.com>

pkg/fission-cli/flag/flag.go

@@ -110,6 +110,7 @@ var (
 	FnTestHeader            = Flag{Type: StringSlice, Name: flagkey.FnTestHeader, Short: "H", Usage: "Request headers"}
 	FnTestQuery             = Flag{Type: StringSlice, Name: flagkey.FnTestQuery, Short: "q", Usage: "Request query parameters: -q key1=value1 -q key2=value2"}
 	FnIdleTimeout           = Flag{Type: Int, Name: flagkey.FnIdleTimeout, Usage: "The length of time (in seconds) that a function is idle before pod(s) are eligible for recycling", DefaultValue: 120}
+	FnConcurrency           = Flag{Type: Int, Name: flagkey.FnConcurrency, Aliases: []string{"con"}, Usage: "Maximum number of pods specialized concurrently to serve requests", DefaultValue: 5}
 
 	HtName              = Flag{Type: String, Name: flagkey.HtName, Usage: "HTTP trigger name"}
 	HtMethod            = Flag{Type: String, Name: flagkey.HtMethod, Usage: "HTTP Method: GET|POST|PUT|DELETE|HEAD", DefaultValue: http.MethodGet}

pkg/fission-cli/flag/key/key.go

@@ -63,6 +63,7 @@ const (
 	FnTestHeader            = "header"
 	FnTestQuery             = "query"
 	FnIdleTimeout           = "idletimeout"
+	FnConcurrency           = "concurrency"
 
 	HtName              = resourceName
 	HtMethod            = "method"