telemetry JK (facebookincubator#441)

Summary:
Pull Request resolved: facebookincubator#441

Install a JK to conditionally enable the telemetry added in the previous Diff

Reviewed By: phlalx

Differential Revision: D55860620

fbshipit-source-id: f532136bad279c8d1eccc8193526f25c611e7285

glean.cabal.in

@@ -1270,6 +1270,7 @@ library glass-lib
         Glean.Glass.SymbolKind
         Glean.Glass.SymbolMap
         Glean.Glass.SymbolSig
+        Glean.Glass.Tracer
         Glean.Glass.Tracing
         Glean.Glass.Utils
         Glean.Glass.Visibility

glean/glass/Glean/Glass/Main.hs

@@ -59,6 +59,7 @@ import Glean.Glass.Types
   ( GlassException (GlassException, glassException_reasons),
     GlassExceptionReason (GlassExceptionReason_exactRevisionNotAvailable))
 import Glean.Glass.Env (Env(tracer))
+import Glean.Glass.Tracer ( isTracingEnabled )
 import Glean.Glass.Tracing (GlassTrace(TraceCommand))
 
 kThriftCacheNoCache :: Text
@@ -153,11 +154,18 @@ withCurrentRepoMapping env0 fn = do
   current <- getRepoMapping
   fn (env0 { Glass.repoMapping = current })
 
+withRequestTracing :: Env -> (Env -> IO b) -> IO b
+withRequestTracing env k = do
+  enabled <- isTracingEnabled
+  k $ if enabled then env else env { tracer = mempty }
+
 -- Actual glass service handler, types from glass.thrift
 -- TODO: snapshot the env, rather than passing in the mutable fields
 --
 glassHandler :: Glass.Env -> GlassServiceCommand r -> IO r
-glassHandler env0 cmd = withCurrentRepoMapping env0 $ \env ->
+glassHandler env0 cmd =
+  withCurrentRepoMapping env0 $ \env1 ->
+  withRequestTracing env1 $ \env ->
   traceMsg (tracer env) (TraceCommand cmd) $ case cmd of
   SuperFacebookService r -> fb303Handler (Glass.fb303 env) r
 

glean/glass/Glean/Glass/Tracer.hs

@@ -0,0 +1,14 @@
+{-
+  Copyright (c) Meta Platforms, Inc. and affiliates.
+  All rights reserved.
+
+  This source code is licensed under the BSD-style license found in the
+  LICENSE file in the root directory of this source tree.
+-}
+
+module Glean.Glass.Tracer
+  ( isTracingEnabled
+  ) where
+
+isTracingEnabled :: IO Bool
+isTracingEnabled = return True