[dbwriter] exponential backoff wait for server start

Summary: When using the database write server process, the parent has to wait for it to fully start up before continuing. Instead of dying after a fixed amount of time, never terminate (external timeouts can take care of that) and use exponential backoff to avoid spamming.

Reviewed By: jvillard

Differential Revision: D23989959

fbshipit-source-id: ff5232c14

infer/src/base/DBWriter.ml

@@ -363,12 +363,16 @@ module Server = struct
     In_channel.close in_channel
 
 
-  let rec retry ~pred ~timeout count =
-    if count < 0 then false
-    else if pred () then true
-    else (
-      Unix.nanosleep timeout |> ignore ;
-      retry ~pred ~timeout (count - 1) )
+  (* wait for socket to appear with 0.1 sec timeout, doubling each time ;
+     choice of numbers is arbitrary *)
+  let initial_wait_for_socket_secs = 0.1
+
+  let rec wait_for_server_start ~wait_secs =
+    Unix.nanosleep wait_secs |> ignore ;
+    if not (socket_exists ()) then (
+      let wait_secs = 2.0 *. wait_secs in
+      L.progress "Waiting for Sqlite write daemon to start (%f seconds)@\n" wait_secs ;
+      wait_for_server_start ~wait_secs )
 
 
   let start () =
@@ -377,10 +381,7 @@ module Server = struct
         ForkUtils.protect ~f:server () ;
         L.exit 0
     | `In_the_parent _child_pid ->
-        (* wait for socket to appear, try 5 times, with a 0.1 sec timeout each time ;
-           choice of numbers is completely arbitrary *)
-        if not (retry ~pred:socket_exists ~timeout:0.1 5) then
-          L.die InternalError "Sqlite write daemon never started@." ;
+        wait_for_server_start ~wait_secs:initial_wait_for_socket_secs ;
         send Command.Handshake
 end