Add logging for proof batch sizes, add MAX_VERIFIER_BATCH_SIZE envvar

src/lib/network_pool/batcher.ml

@@ -147,11 +147,36 @@ let rec start_verifier : type proof partial r.
     (* we looped in the else after verifier finished but no pending work. *)
     t.state <- Waiting ;
     Ivar.fill finished (Ok Outcome.empty) )
-  else
-    let out_for_verification = order_proofs t (Queue.to_list t.queue) in
+  else (
+    [%log debug (Logger.create ())]
+      "Verifying proofs in batch of size $num_proofs"
+      ~metadata:[("num_proofs", Queue.length t.queue)] ;
+    let out_for_verification =
+      let proofs =
+        (* TODO: Make this a proper config detail once we have data on what a
+           good default would be.
+        *)
+        match Sys.getenv_opt "MAX_VERIFIER_BATCH_SIZE" with
+        | None ->
+            let proofs = Queue.to_list t.queue in
+            Queue.clear t.queue ; proofs
+        | Some max_proofs ->
+            (* NB: Order is irrelevant because we sort immediately after *)
+            let rec take n acc =
+              if n > 0 then
+                match Queue.dequeue t.queue with
+                | Some proof ->
+                    take (n - 1) (proof :: acc)
+                | None ->
+                    acc
+              else acc
+            in
+            take n []
+      in
+      order_proofs t proofs
+    in
     let next_finished = Ivar.create () in
     t.state <- Verifying {next_finished; out_for_verification} ;
-    Queue.clear t.queue ;
     let res =
       call_verifier t
         (List.map out_for_verification ~f:(fun (_id, p) -> `Proof p))
@@ -165,7 +190,7 @@ let rec start_verifier : type proof partial r.
               determine_outcome out_for_verification res t
         in
         upon outcome (fun y -> Ivar.fill finished y) ) ;
-    start_verifier t next_finished
+    start_verifier t next_finished )
 
 let verify' (type p r partial n) (t : (p, partial, r) t)
     (proofs : (p, n) Vector.t) :