CP:46157: Add observer_experimental_components flag

Adds a new variable in `Xapi_globs` that is a comma-separeted
string of components. Components in this list will be considered
experimental and therefore disabled by default. They can be
enabled by adding an entry in `xapi.conf` without their name.

For instance, adding the line:

observer-experimental-components = ""

will enable all experimental components.

Signed-off-by: Gabriel Buica <[email protected]>

ocaml/xapi-consts/constants.ml

@@ -398,3 +398,19 @@ let good_ciphersuites =
     ["ECDHE-RSA-AES256-GCM-SHA384"; "ECDHE-RSA-AES128-GCM-SHA256"]
 
 let verify_certificates_path = "/var/xapi/verify-certificates"
+
+let observer_component_xapi = "xapi"
+
+let observer_component_xenopsd = "xenopsd"
+
+let observer_component_xapi_clusterd = "xapi-clusterd"
+
+let observer_component_smapi = "smapi"
+
+let observer_components_all =
+  [
+    observer_component_xapi
+  ; observer_component_xenopsd
+  ; observer_component_xapi_clusterd
+  ; observer_component_smapi
+  ]

ocaml/xapi/xapi_globs.ml

@@ -16,6 +16,7 @@
 
 module String_plain = String (* For when we don't want the Xstringext version *)
 open Xapi_stdext_std.Xstringext
+module StringSet = Set.Make (String)
 
 module D = Debug.Make (struct let name = "xapi_globs" end)
 
@@ -1019,6 +1020,9 @@ let observer_endpoint_https_enabled = ref false
 
 let python3_path = ref "/usr/bin/python3"
 
+let observer_experimental_components =
+  ref (StringSet.singleton Constants.observer_component_smapi)
+
 let xapi_globs_spec =
   [
     ( "master_connection_reset_timeout"
@@ -1515,6 +1519,29 @@ let other_options =
     , (fun () -> string_of_bool !observer_endpoint_https_enabled)
     , "Enable https endpoints to be used by observers"
     )
+  ; ( "observer-experimental-components"
+    , Arg.String
+        (fun s ->
+          observer_experimental_components :=
+            match s with
+            | "" ->
+                StringSet.empty
+            | s ->
+                let input_set =
+                  s |> String.split_on_char ',' |> StringSet.of_list
+                in
+                let valid_set =
+                  Constants.observer_components_all |> StringSet.of_list
+                in
+                StringSet.inter input_set valid_set
+        )
+    , (fun () ->
+        !observer_experimental_components
+        |> StringSet.elements
+        |> String.concat ","
+      )
+    , "Comma-separated list of experimental observer components"
+    )
   ]
 
 (* The options can be set with the variable xapiflags in /etc/sysconfig/xapi.

ocaml/xapi/xapi_observer_components.ml

@@ -12,34 +12,36 @@
  * GNU Lesser General Public License for more details.
  *)
 
+module D = Debug.Make (struct let name = "xapi_observer_components" end)
+
 type t = Xapi | Xenopsd | Xapi_clusterd | SMApi [@@deriving ord]
 
 exception Unsupported_Component of string
 
-let all = [Xapi; Xenopsd; Xapi_clusterd; SMApi]
-
 let to_string = function
   | Xapi ->
-      "xapi"
+      Constants.observer_component_xapi
   | Xenopsd ->
-      "xenopsd"
+      Constants.observer_component_xenopsd
   | Xapi_clusterd ->
-      "xapi-clusterd"
+      Constants.observer_component_xapi_clusterd
   | SMApi ->
-      "smapi"
+      Constants.observer_component_smapi
 
 let of_string = function
-  | "xapi" ->
+  | str when String.equal str Constants.observer_component_xapi ->
       Xapi
-  | "xenopsd" ->
+  | str when String.equal str Constants.observer_component_xenopsd ->
       Xenopsd
-  | "xapi-clusterd" ->
+  | str when String.equal str Constants.observer_component_xapi_clusterd ->
       Xapi_clusterd
-  | "smapi" ->
+  | str when String.equal str Constants.observer_component_smapi ->
       SMApi
   | c ->
       raise (Unsupported_Component c)
 
+let all = List.map of_string Constants.observer_components_all
+
 (* We start up the observer for clusterd only if clusterd has been enabled
    otherwise we initialise clusterd separately in cluster_host so that
    there is no need to restart xapi in order for clusterd to be observed.
@@ -54,8 +56,21 @@ let assert_valid_components components =
   with Unsupported_Component component ->
     raise Api_errors.(Server_error (invalid_value, ["component"; component]))
 
+let filter_out_exp_components components =
+  let open Xapi_globs in
+  let component_set = components |> List.map to_string |> StringSet.of_list in
+  StringSet.diff component_set !observer_experimental_components
+  |> StringSet.elements
+  |> List.map of_string
+
 let observed_components_of components =
-  match components with [] -> startup_components () | components -> components
+  ( match components with
+  | [] ->
+      startup_components ()
+  | components ->
+      components
+  )
+  |> filter_out_exp_components
 
 let is_component_enabled ~component =
   try