diff --git a/src/bin_node/node_config_file.ml b/src/bin_node/node_config_file.ml
index 0433adee7..356852f8e 100644
--- a/src/bin_node/node_config_file.ml
+++ b/src/bin_node/node_config_file.ml
@@ -54,6 +54,7 @@ and log = {
 
 and shell = {
   bootstrap_threshold : int ;
+  block_validator_limits : Node.block_validator_limits ;
   prevalidator_limits : Node.prevalidator_limits ;
   timeout : Node.timeout ;
 }
@@ -105,6 +106,15 @@ let default_log = {
 
 let default_shell = {
   bootstrap_threshold = 4 ;
+  block_validator_limits = {
+    protocol_timeout = 120. ;
+    worker_limits = {
+      backlog_size = 1000 ;
+      backlog_level = Logging.Debug ;
+      zombie_lifetime = 3600. ;
+      zombie_memory = 1800. ;
+    }
+  } ;
   prevalidator_limits = {
     operation_timeout = 10. ;
     max_refused_operations = 1000 ;
@@ -284,6 +294,23 @@ let worker_limits_encoding
 let timeout_encoding =
   Data_encoding.ranged_float 0. 500.
 
+let block_validator_limits_encoding =
+  let open Data_encoding in
+  conv
+    (fun { Node.protocol_timeout ; worker_limits } ->
+       (protocol_timeout, worker_limits))
+    (fun (protocol_timeout, worker_limits) ->
+       { protocol_timeout ; worker_limits})
+    (merge_objs
+       (obj1
+          (dft "protocol_request_timeout" timeout_encoding
+             default_shell.block_validator_limits.protocol_timeout))
+       (worker_limits_encoding
+          default_shell.block_validator_limits.worker_limits.backlog_size
+          default_shell.block_validator_limits.worker_limits.backlog_level
+          default_shell.block_validator_limits.worker_limits.zombie_lifetime
+          default_shell.block_validator_limits.worker_limits.zombie_memory))
+
 let prevalidator_limits_encoding =
   let open Data_encoding in
   conv
@@ -325,13 +352,19 @@ let timeout_encoding =
 let shell =
   let open Data_encoding in
   conv
-    (fun { bootstrap_threshold ; timeout ; prevalidator_limits } ->
-       bootstrap_threshold, timeout, prevalidator_limits)
-    (fun (bootstrap_threshold, timeout, prevalidator_limits) ->
-       { bootstrap_threshold ; timeout ; prevalidator_limits })
-    (obj3
+    (fun { bootstrap_threshold ; timeout ;
+           block_validator_limits ; prevalidator_limits } ->
+      bootstrap_threshold, timeout,
+      block_validator_limits, prevalidator_limits)
+    (fun (bootstrap_threshold, timeout,
+          block_validator_limits, prevalidator_limits) ->
+      { bootstrap_threshold ; timeout ;
+        block_validator_limits ;
+        prevalidator_limits })
+    (obj4
        (dft "bootstrap_threshold" uint8 default_shell.bootstrap_threshold)
        (dft "timeout" timeout_encoding default_shell.timeout)
+       (dft "block_validator" block_validator_limits_encoding default_shell.block_validator_limits)
        (dft "prevalidator" prevalidator_limits_encoding default_shell.prevalidator_limits)
     )
 
@@ -451,6 +484,7 @@ let update
         ~default:cfg.shell.bootstrap_threshold
         bootstrap_threshold ;
     timeout = cfg.shell.timeout ;
+    block_validator_limits = cfg.shell.block_validator_limits ;
     prevalidator_limits = cfg.shell.prevalidator_limits ;
   }
   in
diff --git a/src/bin_node/node_config_file.mli b/src/bin_node/node_config_file.mli
index 25002d6f9..917551e8a 100644
--- a/src/bin_node/node_config_file.mli
+++ b/src/bin_node/node_config_file.mli
@@ -44,6 +44,7 @@ and log = {
 
 and shell = {
   bootstrap_threshold : int ;
+  block_validator_limits : Node.block_validator_limits ;
   prevalidator_limits : Node.prevalidator_limits ;
   timeout : Node.timeout ;
 }
diff --git a/src/bin_node/node_run_command.ml b/src/bin_node/node_run_command.ml
index edc7ddd6a..040905929 100644
--- a/src/bin_node/node_run_command.ml
+++ b/src/bin_node/node_run_command.ml
@@ -173,6 +173,7 @@ let init_node ?sandbox (config : Node_config_file.t) =
   Node.create
     node_config
     config.shell.timeout
+    config.shell.block_validator_limits
     config.shell.prevalidator_limits
 
 let () =
diff --git a/src/lib_node_shell/block_validator.ml b/src/lib_node_shell/block_validator.ml
index 6b21a97fe..c448b608d 100644
--- a/src/lib_node_shell/block_validator.ml
+++ b/src/lib_node_shell/block_validator.ml
@@ -7,294 +7,58 @@
 (*                                                                        *)
 (**************************************************************************)
 
-include Logging.Make(struct let name = "node.validator.block" end)
-
-type 'a request =
-  | Request_validation: {
-      net_db: Distributed_db.net_db ;
-      notify_new_block: State.Block.t -> unit ;
-      canceler: Lwt_canceler.t option ;
-      peer: P2p.Peer_id.t option ;
-      hash: Block_hash.t ;
-      header: Block_header.t ;
-      operations: Operation.t list list ;
-    } -> State.Block.t tzresult request
-
-type message = Message: 'a request * 'a Lwt.u option -> message
-
-type t = {
-  protocol_validator: Protocol_validator.t ;
-  protocol_timeout: float ;
-  mutable worker: unit Lwt.t ;
-  messages: message Lwt_pipe.t ;
-  canceler: Lwt_canceler.t ;
-}
-
-(** Block validation *)
-
-type block_error =
-  | Cannot_parse_operation of Operation_hash.t
-  | Invalid_fitness of { expected: Fitness.t ; found: Fitness.t }
-  | Non_increasing_timestamp
-  | Non_increasing_fitness
-  | Invalid_level of { expected: Int32.t ; found: Int32.t }
-  | Invalid_proto_level of { expected: int ; found: int }
-  | Replayed_operation of Operation_hash.t
-  | Outdated_operation of
-      { operation: Operation_hash.t;
-        originating_block: Block_hash.t }
-  | Expired_network of
-      { net_id: Net_id.t ;
-        expiration: Time.t ;
-        timestamp: Time.t ;
-      }
-  | Unexpected_number_of_validation_passes of int (* uint8 *)
-  | Too_many_operations of { pass: int; found: int; max: int }
-  | Oversized_operation of { operation: Operation_hash.t;
-                             size: int; max: int }
-
-let block_error_encoding =
-  let open Data_encoding in
-  union
-    [
-      case (Tag 0)
-        (obj2
-           (req "error" (constant "cannot_parse_operation"))
-           (req "operation" Operation_hash.encoding))
-        (function Cannot_parse_operation operation -> Some ((), operation)
-                | _ -> None)
-        (fun ((), operation) -> Cannot_parse_operation operation) ;
-      case (Tag 1)
-        (obj3
-           (req "error" (constant "invalid_fitness"))
-           (req "expected" Fitness.encoding)
-           (req "found" Fitness.encoding))
-        (function
-          | Invalid_fitness { expected ; found } ->
-              Some ((), expected, found)
-          | _ -> None)
-        (fun ((), expected, found) -> Invalid_fitness { expected ; found }) ;
-      case (Tag 2)
-        (obj1
-           (req "error" (constant "non_increasing_timestamp")))
-        (function Non_increasing_timestamp -> Some ()
-                | _ -> None)
-        (fun () -> Non_increasing_timestamp) ;
-      case (Tag 3)
-        (obj1
-           (req "error" (constant "non_increasing_fitness")))
-        (function Non_increasing_fitness -> Some ()
-                | _ -> None)
-        (fun () -> Non_increasing_fitness) ;
-      case (Tag 4)
-        (obj3
-           (req "error" (constant "invalid_level"))
-           (req "expected" int32)
-           (req "found" int32))
-        (function
-          | Invalid_level { expected ; found } ->
-              Some ((), expected, found)
-          | _ -> None)
-        (fun ((), expected, found) -> Invalid_level { expected ; found }) ;
-      case (Tag 5)
-        (obj3
-           (req "error" (constant "invalid_proto_level"))
-           (req "expected" uint8)
-           (req "found" uint8))
-        (function
-          | Invalid_proto_level { expected ; found } ->
-              Some ((), expected, found)
-          | _ -> None)
-        (fun ((), expected, found) ->
-           Invalid_proto_level { expected ; found }) ;
-      case (Tag 6)
-        (obj2
-           (req "error" (constant "replayed_operation"))
-           (req "operation" Operation_hash.encoding))
-        (function Replayed_operation operation -> Some ((), operation)
-                | _ -> None)
-        (fun ((), operation) -> Replayed_operation operation) ;
-      case (Tag 7)
-        (obj3
-           (req "error" (constant "outdated_operation"))
-           (req "operation" Operation_hash.encoding)
-           (req "originating_block" Block_hash.encoding))
-        (function
-          | Outdated_operation { operation ; originating_block } ->
-              Some ((), operation, originating_block)
-          | _ -> None)
-        (fun ((), operation, originating_block) ->
-           Outdated_operation { operation ; originating_block }) ;
-      case (Tag 8)
-        (obj2
-           (req "error" (constant "unexpected_number_of_passes"))
-           (req "found" uint8))
-        (function
-          | Unexpected_number_of_validation_passes n -> Some ((), n)
-          | _ -> None)
-        (fun ((), n) -> Unexpected_number_of_validation_passes n) ;
-      case (Tag 9)
-        (obj4
-           (req "error" (constant "too_many_operations"))
-           (req "validation_pass" uint8)
-           (req "found" uint16)
-           (req "max" uint16))
-        (function
-          | Too_many_operations { pass ; found ; max } ->
-              Some ((), pass, found, max)
-          | _ -> None)
-        (fun ((), pass, found, max) ->
-           Too_many_operations { pass ; found ; max }) ;
-      case (Tag 10)
-        (obj4
-           (req "error" (constant "oversized_operation"))
-           (req "operation" Operation_hash.encoding)
-           (req "found" int31)
-           (req "max" int31))
-        (function
-          | Oversized_operation { operation ; size ; max } ->
-              Some ((), operation, size, max)
-          | _ -> None)
-        (fun ((), operation, size, max) ->
-           Oversized_operation { operation ; size ; max }) ;
-    ]
-
-let pp_block_error ppf = function
-  | Cannot_parse_operation oph ->
-      Format.fprintf ppf
-        "Failed to parse the operation %a."
-        Operation_hash.pp_short oph
-  | Invalid_fitness { expected ; found } ->
-      Format.fprintf ppf
-        "@[<v 2>Invalid fitness:@ \
-        \ expected %a@ \
-        \ found %a@]"
-        Fitness.pp expected
-        Fitness.pp found
-  | Non_increasing_timestamp ->
-      Format.fprintf ppf "Non increasing timestamp"
-  | Non_increasing_fitness ->
-      Format.fprintf ppf "Non increasing fitness"
-  | Invalid_level { expected ; found } ->
-      Format.fprintf ppf
-        "Invalid level:@ \
-        \ expected %ld@ \
-        \ found %ld"
-        expected
-        found
-  | Invalid_proto_level { expected ; found } ->
-      Format.fprintf ppf
-        "Invalid protocol level:@ \
-        \ expected %d@ \
-        \ found %d"
-        expected
-        found
-  | Replayed_operation oph ->
-      Format.fprintf ppf
-        "The operation %a was previously included in the chain."
-        Operation_hash.pp_short oph
-  | Outdated_operation { operation ; originating_block } ->
-      Format.fprintf ppf
-        "The operation %a is outdated (originated in block: %a)"
-        Operation_hash.pp_short operation
-        Block_hash.pp_short originating_block
-  | Expired_network { net_id ; expiration ; timestamp } ->
-      Format.fprintf ppf
-        "The block timestamp (%a) is later than \
-         its network expiration date: %a (net: %a)."
-        Time.pp_hum timestamp
-        Time.pp_hum expiration
-        Net_id.pp_short net_id
-  | Unexpected_number_of_validation_passes n ->
-      Format.fprintf ppf
-        "Invalid number of validation passes (found: %d)"
-        n
-  | Too_many_operations { pass ; found ; max } ->
-      Format.fprintf ppf
-        "Too many operations in validation pass %d (found: %d, max: %d)"
-        pass found max
-  | Oversized_operation { operation ; size ; max } ->
-      Format.fprintf ppf
-        "Oversized operation %a (size: %d, max: %d)"
-        Operation_hash.pp_short operation size max
-
-type error +=
-  | Invalid_block of
-      { block: Block_hash.t ; error: block_error }
-  | Unavailable_protocol of
-      { block: Block_hash.t ; protocol: Protocol_hash.t }
-  | Inconsistent_operations_hash of
-      { block: Block_hash.t ;
-        expected: Operation_list_list_hash.t ;
-        found: Operation_list_list_hash.t }
-
+open Block_validator_worker_state
+open Block_validator_errors
 let invalid_block block error = Invalid_block { block ; error }
 
-let () =
-  Error_monad.register_error_kind
-    `Permanent
-    ~id:"validator.invalid_block"
-    ~title:"Invalid block"
-    ~description:"Invalid block."
-    ~pp:begin fun ppf (block, error) ->
-      Format.fprintf ppf
-        "@[<v 2>Invalid block %a@ %a@]"
-        Block_hash.pp_short block pp_block_error error
-    end
-    Data_encoding.(merge_objs
-                     (obj1 (req "invalid_block" Block_hash.encoding))
-                     block_error_encoding)
-    (function Invalid_block { block ; error } ->
-       Some (block, error) | _ -> None)
-    (fun (block, error) ->
-       Invalid_block { block ; error }) ;
-  Error_monad.register_error_kind
-    `Temporary
-    ~id:"validator.unavailable_protocol"
-    ~title:"Missing protocol"
-    ~description:"The protocol required for validating a block is missing."
-    ~pp:begin fun ppf (block, protocol) ->
-      Format.fprintf ppf
-        "Missing protocol (%a) when validating the block %a."
-        Protocol_hash.pp_short protocol
-        Block_hash.pp_short block
-    end
-    Data_encoding.(
-      obj2
-        (req "block" Block_hash.encoding)
-        (req "missing_protocol" Protocol_hash.encoding))
-    (function
-      | Unavailable_protocol { block ; protocol } ->
-          Some (block, protocol)
-      | _ -> None)
-    (fun (block, protocol) -> Unavailable_protocol { block ; protocol }) ;
-  Error_monad.register_error_kind
-    `Temporary
-    ~id:"validator.inconsistent_operations_hash"
-    ~title:"Invalid merkle tree"
-    ~description:"The provided list of operations is inconsistent with \
-                  the block header."
-    ~pp:begin fun ppf (block, expected, found) ->
-      Format.fprintf ppf
-        "@[<v 2>The provided list of operations for block %a \
-        \ is inconsistent with the block header@ \
-        \ expected: %a@ \
-        \ found: %a@]"
-        Block_hash.pp_short block
-        Operation_list_list_hash.pp_short expected
-        Operation_list_list_hash.pp_short found
-    end
-    Data_encoding.(
-      obj3
-        (req "block" Block_hash.encoding)
-        (req "expected" Operation_list_list_hash.encoding)
-        (req "found" Operation_list_list_hash.encoding))
-    (function
-      | Inconsistent_operations_hash { block ; expected ; found } ->
-          Some (block, expected, found)
-      | _ -> None)
-    (fun (block, expected, found) ->
-       Inconsistent_operations_hash { block ; expected ; found })
+type limits = {
+  protocol_timeout: float ;
+  worker_limits : Worker_types.limits ;
+}
+
+module Name = struct
+  type t = unit
+  let encoding = Data_encoding.empty
+  let base = [ "validator.block" ]
+  let pp _ () = ()
+end
+
+module Types = struct
+  include Worker_state
+  type state = {
+    protocol_validator: Protocol_validator.t ;
+    limits : limits ;
+  }
+  type parameters = limits * Distributed_db.t
+  let view _state _parameters = ()
+end
+
+module Request = struct
+  include Request
+  type 'a t =
+    | Request_validation : {
+        net_db: Distributed_db.net_db ;
+        notify_new_block: State.Block.t -> unit ;
+        canceler: Lwt_canceler.t option ;
+        peer: P2p.Peer_id.t option ;
+        hash: Block_hash.t ;
+        header: Block_header.t ;
+        operations: Operation.t list list ;
+      } -> State.Block.t tzresult t
+  let view
+    : type a. a t -> view
+    = fun (Request_validation { net_db ; peer ; hash }) ->
+      let net_id = net_db |> Distributed_db.net_state |> State.Net.id in
+      { net_id ; block = hash ; peer = peer }
+end
+
+module Worker = Worker.Make (Name) (Event) (Request) (Types)
+
+type t = Worker.infinite Worker.queue Worker.t
+type error += Closed = Worker.Closed
+
+let debug w =
+  Format.kasprintf (fun msg -> Worker.record_event w (Debug msg))
 
 let check_header
     (pred: State.Block.t) hash (header: Block_header.t) =
@@ -442,137 +206,124 @@ let get_proto pred hash =
                                    protocol = pred_protocol_hash })
   | Some p -> return p
 
-let rec worker_loop bv =
-  begin
-    Lwt_utils.protect ~canceler:bv.canceler begin fun () ->
-      Lwt_pipe.pop bv.messages >>= return
-    end >>=? fun (Message (request, wakener)) ->
-    let may_wakeup =
-      match wakener with
-      | None -> (fun _ -> ())
-      | Some wakener -> (fun v -> Lwt.wakeup_later wakener v)
-    in
-    match request with
-    | Request_validation { net_db ; notify_new_block ; canceler ;
-                           peer ; hash ; header ; operations } ->
-        let net_state = Distributed_db.net_state net_db in
-        State.Block.read_opt net_state hash >>= function
-        | Some block ->
-            lwt_debug "previously validated block %a (after pipe)"
-              Block_hash.pp_short hash >>= fun () ->
-            Protocol_validator.prefetch_and_compile_protocols
-              bv.protocol_validator
-              ?peer ~timeout:bv.protocol_timeout
-              block ;
-            may_wakeup (Ok block) ;
-            return ()
+let on_request
+  : type r. t -> r Request.t -> r tzresult Lwt.t
+  = fun w
+    (Request.Request_validation
+       { net_db ; notify_new_block ; canceler ;
+         peer ; hash ; header ; operations }) ->
+    let bv = Worker.state w in
+    let net_state = Distributed_db.net_state net_db in
+    State.Block.read_opt net_state hash >>= function
+    | Some block ->
+        debug w "previously validated block %a (after pipe)"
+          Block_hash.pp_short hash ;
+        Protocol_validator.prefetch_and_compile_protocols
+          bv.protocol_validator
+          ?peer ~timeout:bv.limits.protocol_timeout
+          block ;
+        return (Ok block)
+    | None ->
+        State.Block.read_invalid net_state hash >>= function
+        | Some { errors } ->
+            return (Error errors)
         | None ->
-            State.Block.read_invalid net_state hash >>= function
-            | Some { errors } ->
-                may_wakeup (Error errors) ;
-                return ()
-            | None ->
-                begin
-                  lwt_debug "validating block %a"
-                    Block_hash.pp_short hash >>= fun () ->
-                  State.Block.read
-                    net_state header.shell.predecessor >>=? fun pred ->
-                  get_proto pred hash >>=? fun proto ->
-                  (* TODO also protect with [bv.canceler]. *)
-                  Lwt_utils.protect ?canceler begin fun () ->
-                    apply_block
-                      (Distributed_db.net_state net_db)
-                      pred proto hash header operations
-                  end
-                end >>= function
-                | Ok result -> begin
-                    Lwt_utils.protect ~canceler:bv.canceler begin fun () ->
-                      Distributed_db.commit_block
-                        net_db hash header operations result
-                    end >>=? function
-                    | None ->
-                        assert false (* should not happen *)
-                    | Some block ->
-                        lwt_log_info "validated block %a"
-                          Block_hash.pp_short hash >>= fun () ->
-                        Protocol_validator.prefetch_and_compile_protocols
-                          bv.protocol_validator
-                          ?peer ~timeout:bv.protocol_timeout
-                          block ;
-                        may_wakeup (Ok block) ;
-                        notify_new_block block ;
-                        return ()
-                  end
-                (* TODO catch other temporary error (e.g. system errors)
-                   and do not 'commit' them on disk... *)
-                | Error [Lwt_utils.Canceled | Unavailable_protocol _] as err ->
-                    may_wakeup err ;
-                    return ()
-                | Error errors as err ->
-                    lwt_log_error "@[<v 2>Received invalid block %a:@ %a@]"
-                      Block_hash.pp_short hash
-                      Error_monad.pp_print_error errors >>= fun () ->
-                    Lwt_utils.protect ~canceler:bv.canceler begin fun () ->
-                      Distributed_db.commit_invalid_block
-                        net_db hash header errors
-                    end >>=? fun commited ->
-                    assert commited ;
-                    may_wakeup err ;
-                    return ()
-  end >>= function
-  | Ok () ->
-      worker_loop bv
-  | Error [Exn (Unix.Unix_error _) as err] ->
-      lwt_log_error "validation failed with %a"
-        pp_print_error [err] >>= fun () ->
-      worker_loop bv
-  | Error [Lwt_utils.Canceled | Exn Lwt_pipe.Closed] ->
-      lwt_log_notice "terminating" >>= fun () ->
-      Lwt.return_unit
-  | Error err ->
-      lwt_log_error "@[Unexpected error:@ %a@]"
-        pp_print_error err >>= fun () ->
-      Lwt_canceler.cancel bv.canceler >>= fun () ->
-      Lwt.return_unit
+            begin
+              debug w "validating block %a" Block_hash.pp_short hash ;
+              State.Block.read
+                net_state header.shell.predecessor >>=? fun pred ->
+              get_proto pred hash >>=? fun proto ->
+              (* TODO also protect with [Worker.canceler w]. *)
+              Lwt_utils.protect ?canceler begin fun () ->
+                apply_block
+                  (Distributed_db.net_state net_db)
+                  pred proto hash header operations
+              end
+            end >>= function
+            | Ok result -> begin
+                Worker.protect w begin fun () ->
+                  Distributed_db.commit_block
+                    net_db hash header operations result
+                end >>=? function
+                | None ->
+                    assert false (* should not happen *)
+                | Some block ->
+                    Protocol_validator.prefetch_and_compile_protocols
+                      bv.protocol_validator
+                      ?peer ~timeout:bv.limits.protocol_timeout
+                      block ;
+                    notify_new_block block ;
+                    return (Ok block)
+              end
+            (* TODO catch other temporary error (e.g. system errors)
+               and do not 'commit' them on disk... *)
+            | Error [Lwt_utils.Canceled | Unavailable_protocol _] as err ->
+                return err
+            | Error errors ->
+                Worker.protect w begin fun () ->
+                  Distributed_db.commit_invalid_block
+                    net_db hash header errors
+                end >>=? fun commited ->
+                assert commited ;
+                return (Error errors)
 
-let create ~protocol_timeout db =
+let on_launch _ _ (limits, db) =
   let protocol_validator = Protocol_validator.create db in
-  let canceler = Lwt_canceler.create () in
-  let messages = Lwt_pipe.create () in
-  let bv = {
-    protocol_validator ;
-    protocol_timeout ;
-    canceler ; messages ;
-    worker = Lwt.return_unit } in
-  Lwt_canceler.on_cancel bv.canceler begin fun () ->
-    Lwt_pipe.close bv.messages ;
-    Lwt.return_unit
-  end ;
-  bv.worker <-
-    Lwt_utils.worker "block_validator"
-      ~run:(fun () -> worker_loop bv)
-      ~cancel:(fun () -> Lwt_canceler.cancel bv.canceler) ;
-  bv
+  Lwt.return { Types.protocol_validator ; limits }
 
-let shutdown { canceler ; worker } =
-  Lwt_canceler.cancel canceler >>= fun () ->
-  worker
+let on_error w r st errs =
+  Worker.record_event w (Validation_failure (r, st, errs)) ;
+  Lwt.return (Error errs)
 
-let validate { messages ; protocol_validator ; protocol_timeout }
+let on_completion
+  : type a. t -> a Request.t -> a -> Worker_types.request_status -> unit Lwt.t
+  = fun w (Request.Request_validation _ as r) v st ->
+    match v with
+    | Ok _ ->
+        Worker.record_event w
+          (Event.Validation_success (Request.view r, st)) ;
+        Lwt.return ()
+    | Error errs ->
+        Worker.record_event w
+          (Event.Validation_failure (Request.view r, st, errs)) ;
+        Lwt.return ()
+
+let table = Worker.create_table Queue
+
+let create limits db =
+  let module Handlers = struct
+    type self = t
+    let on_launch = on_launch
+    let on_request = on_request
+    let on_close _ = Lwt.return ()
+    let on_error = on_error
+    let on_completion = on_completion
+    let on_no_request _ = return ()
+  end in
+  Worker.launch
+    table
+    limits.worker_limits
+    ()
+    (limits, db)
+    (module Handlers)
+
+let shutdown = Worker.shutdown
+
+let validate w
     ?canceler ?peer ?(notify_new_block = fun _ -> ())
     net_db hash (header : Block_header.t) operations =
+  let bv = Worker.state w in
   let net_state = Distributed_db.net_state net_db in
   State.Block.read_opt net_state hash >>= function
   | Some block ->
-      lwt_debug "previously validated block %a (before pipe)"
-        Block_hash.pp_short hash >>= fun () ->
+      debug w "previously validated block %a (before pipe)"
+        Block_hash.pp_short hash ;
       Protocol_validator.prefetch_and_compile_protocols
-        protocol_validator
-        ?peer ~timeout:protocol_timeout
+        bv.protocol_validator
+        ?peer ~timeout:bv.limits.protocol_timeout
         block ;
       return block
   | None ->
-      let res, wakener = Lwt.task () in
       map_p (map_p (fun op ->
           let op_hash = Operation.hash op in
           return op_hash))
@@ -589,14 +340,25 @@ let validate { messages ; protocol_validator ; protocol_timeout }
             found = computed_hash ;
           }) >>=? fun () ->
       check_net_liveness net_db hash header >>=? fun () ->
-      lwt_debug "pushing validation request for block %a"
-        Block_hash.pp_short hash >>= fun () ->
-      Lwt_pipe.push messages
-        (Message (Request_validation
-                    { net_db ; notify_new_block ; canceler ;
-                      peer ; hash ; header ; operations },
-                  Some wakener)) >>= fun () ->
-      res
+      Worker.push_request_and_wait w
+        (Request_validation
+           { net_db ; notify_new_block ; canceler ;
+             peer ; hash ; header ; operations }) >>=? fun result ->
+      Lwt.return result
 
-let fetch_and_compile_protocol bv =
+let fetch_and_compile_protocol w =
+  let bv = Worker.state w in
   Protocol_validator.fetch_and_compile_protocol bv.protocol_validator
+
+let status = Worker.status
+
+let running_worker () =
+  match Worker.list table with
+  | (_, single) :: _ -> single
+  | [] -> raise Not_found
+
+let pending_requests t = Worker.pending_requests t
+
+let current_request t = Worker.current_request t
+
+let last_events = Worker.last_events
diff --git a/src/lib_node_shell/block_validator.mli b/src/lib_node_shell/block_validator.mli
index 7436d14b4..484039f87 100644
--- a/src/lib_node_shell/block_validator.mli
+++ b/src/lib_node_shell/block_validator.mli
@@ -9,40 +9,15 @@
 
 type t
 
-type block_error =
-  | Cannot_parse_operation of Operation_hash.t
-  | Invalid_fitness of { expected: Fitness.t ; found: Fitness.t }
-  | Non_increasing_timestamp
-  | Non_increasing_fitness
-  | Invalid_level of { expected: Int32.t ; found: Int32.t }
-  | Invalid_proto_level of { expected: int ; found: int }
-  | Replayed_operation of Operation_hash.t
-  | Outdated_operation of
-      { operation: Operation_hash.t;
-        originating_block: Block_hash.t }
-  | Expired_network of
-      { net_id: Net_id.t ;
-        expiration: Time.t ;
-        timestamp: Time.t ;
-      }
-  | Unexpected_number_of_validation_passes of int (* uint8 *)
-  | Too_many_operations of { pass: int; found: int; max: int }
-  | Oversized_operation of { operation: Operation_hash.t;
-                             size: int; max: int }
+type limits = {
+  protocol_timeout: float ;
+  worker_limits : Worker_types.limits ;
+}
 
-type error +=
-  | Invalid_block of
-      { block: Block_hash.t ; error: block_error }
-  | Unavailable_protocol of
-      { block: Block_hash.t ; protocol: Protocol_hash.t }
-  | Inconsistent_operations_hash of
-      { block: Block_hash.t ;
-        expected: Operation_list_list_hash.t ;
-        found: Operation_list_list_hash.t }
+type error += Closed of unit
 
 val create:
-  protocol_timeout:float ->
-  Distributed_db.t -> t
+  limits -> Distributed_db.t -> t Lwt.t
 
 val validate:
   t ->
@@ -60,3 +35,10 @@ val fetch_and_compile_protocol:
   Protocol_hash.t -> State.Registred_protocol.t tzresult Lwt.t
 
 val shutdown: t -> unit Lwt.t
+
+val running_worker: unit -> t
+val status: t -> Worker_types.worker_status
+
+val pending_requests : t -> (Time.t * Block_validator_worker_state.Request.view) list
+val current_request : t -> (Time.t * Time.t * Block_validator_worker_state.Request.view) option
+val last_events : t -> (Lwt_log_core.level * Block_validator_worker_state.Event.t list) list
diff --git a/src/lib_node_shell/bootstrap_pipeline.ml b/src/lib_node_shell/bootstrap_pipeline.ml
index d844847f3..80effe5c9 100644
--- a/src/lib_node_shell/bootstrap_pipeline.ml
+++ b/src/lib_node_shell/bootstrap_pipeline.ml
@@ -170,8 +170,8 @@ let rec validation_worker_loop pipeline =
   | Ok () -> validation_worker_loop pipeline
   | Error [Exn Lwt.Canceled | Lwt_utils.Canceled | Exn Lwt_pipe.Closed] ->
       Lwt.return_unit
-  | Error ([ Block_validator.Invalid_block _
-           | Block_validator.Unavailable_protocol _ ] as err ) ->
+  | Error ([ Block_validator_errors.Invalid_block _
+           | Block_validator_errors.Unavailable_protocol _ ] as err ) ->
       (* Propagate the error to the peer validator. *)
       pipeline.errors <- pipeline.errors @ err ;
       Lwt_canceler.cancel pipeline.canceler >>= fun () ->
diff --git a/src/lib_node_shell/node.ml b/src/lib_node_shell/node.ml
index 3671658a5..7a59d398c 100644
--- a/src/lib_node_shell/node.ml
+++ b/src/lib_node_shell/node.ml
@@ -102,6 +102,11 @@ and prevalidator_limits = Prevalidator.limits = {
   worker_limits : Worker_types.limits ;
 }
 
+and block_validator_limits = Block_validator.limits = {
+  protocol_timeout: float ;
+  worker_limits : Worker_types.limits ;
+}
+
 let may_create_net state genesis =
   State.Net.get state (Net_id.of_block_hash genesis.State.Net.block) >>= function
   | Ok net -> Lwt.return net
@@ -112,13 +117,15 @@ let create { genesis ; store_root ; context_root ;
              patch_context ; p2p = net_params ;
              test_network_max_tll = max_child_ttl ;
              bootstrap_threshold }
-    timeout prevalidator_limits =
+    timeout
+    block_validator_limits
+    prevalidator_limits =
   init_p2p net_params >>=? fun p2p ->
   State.read
     ~store_root ~context_root ?patch_context () >>=? fun state ->
   let distributed_db = Distributed_db.create state p2p in
-  let validator =
-    Validator.create state distributed_db timeout prevalidator_limits in
+  Validator.create state distributed_db timeout
+    block_validator_limits prevalidator_limits >>= fun validator ->
   may_create_net state genesis >>= fun mainnet_state ->
   Validator.activate validator
     ~bootstrap_threshold
diff --git a/src/lib_node_shell/node.mli b/src/lib_node_shell/node.mli
index 1b0cfd125..d9be11501 100644
--- a/src/lib_node_shell/node.mli
+++ b/src/lib_node_shell/node.mli
@@ -30,8 +30,17 @@ and prevalidator_limits = {
   operation_timeout: float ;
   worker_limits : Worker_types.limits ;
 }
+and block_validator_limits = {
+  protocol_timeout: float ;
+  worker_limits : Worker_types.limits ;
+}
 
-val create: config -> timeout -> prevalidator_limits -> t tzresult Lwt.t
+val create:
+  config ->
+  timeout ->
+  block_validator_limits ->
+  prevalidator_limits ->
+  t tzresult Lwt.t
 
 module RPC : sig
 
diff --git a/src/lib_node_shell/peer_validator.ml b/src/lib_node_shell/peer_validator.ml
index c782eb920..f4497c8df 100644
--- a/src/lib_node_shell/peer_validator.ml
+++ b/src/lib_node_shell/peer_validator.ml
@@ -200,7 +200,7 @@ let rec worker_loop pv =
       lwt_debug "%a" Error_monad.pp_print_error errors >>= fun () ->
       Lwt_canceler.cancel pv.canceler >>= fun () ->
       Lwt.return_unit
-  | Error [Block_validator.Unavailable_protocol { protocol } ] -> begin
+  | Error [Block_validator_errors.Unavailable_protocol { protocol } ] -> begin
       Block_validator.fetch_and_compile_protocol
         pv.block_validator
         ~peer:pv.peer_id
diff --git a/src/lib_node_shell/validator.ml b/src/lib_node_shell/validator.ml
index 1b23eccf0..d73742a03 100644
--- a/src/lib_node_shell/validator.ml
+++ b/src/lib_node_shell/validator.ml
@@ -15,6 +15,7 @@ type t = {
   db: Distributed_db.t ;
   block_validator: Block_validator.t ;
   timeout: Net_validator.timeout ;
+  block_validator_limits: Block_validator.limits ;
   prevalidator_limits: Prevalidator.limits ;
 
   valid_block_input: State.Block.t Lwt_watcher.input ;
@@ -22,16 +23,17 @@ type t = {
 
 }
 
-let create state db timeout prevalidator_limits =
-  let block_validator =
-    Block_validator.create
-      ~protocol_timeout:timeout.Net_validator.protocol
-      db in
+let create state db timeout
+    block_validator_limits
+    prevalidator_limits =
+  Block_validator.create block_validator_limits db >>= fun block_validator ->
   let valid_block_input = Lwt_watcher.create_input () in
-  { state ; db ; timeout ; prevalidator_limits ; block_validator ;
-    valid_block_input ;
-    active_nets = Net_id.Table.create 7 ;
-  }
+  Lwt.return
+    { state ; db ; timeout ; block_validator ;
+      prevalidator_limits ; block_validator_limits ;
+      valid_block_input ;
+      active_nets = Net_id.Table.create 7 ;
+    }
 
 let activate v ?bootstrap_threshold ?max_child_ttl net_state =
   let net_id = State.Net.id net_state in
diff --git a/src/lib_node_shell/validator.mli b/src/lib_node_shell/validator.mli
index 80b1d866a..397fc215c 100644
--- a/src/lib_node_shell/validator.mli
+++ b/src/lib_node_shell/validator.mli
@@ -15,8 +15,9 @@ val create:
   State.t ->
   Distributed_db.t ->
   Net_validator.timeout ->
+  Block_validator.limits ->
   Prevalidator.limits ->
-  t
+  t Lwt.t
 val shutdown: t -> unit Lwt.t
 
 (** Start the validation scheduler of a given network. *)
diff --git a/src/lib_node_shell_base/block_validator_errors.ml b/src/lib_node_shell_base/block_validator_errors.ml
new file mode 100644
index 000000000..6e43f2e60
--- /dev/null
+++ b/src/lib_node_shell_base/block_validator_errors.ml
@@ -0,0 +1,271 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+type block_error =
+  | Cannot_parse_operation of Operation_hash.t
+  | Invalid_fitness of { expected: Fitness.t ; found: Fitness.t }
+  | Non_increasing_timestamp
+  | Non_increasing_fitness
+  | Invalid_level of { expected: Int32.t ; found: Int32.t }
+  | Invalid_proto_level of { expected: int ; found: int }
+  | Replayed_operation of Operation_hash.t
+  | Outdated_operation of
+      { operation: Operation_hash.t;
+        originating_block: Block_hash.t }
+  | Expired_network of
+      { net_id: Net_id.t ;
+        expiration: Time.t ;
+        timestamp: Time.t ;
+      }
+  | Unexpected_number_of_validation_passes of int (* uint8 *)
+  | Too_many_operations of { pass: int; found: int; max: int }
+  | Oversized_operation of { operation: Operation_hash.t;
+                             size: int; max: int }
+
+let block_error_encoding =
+  let open Data_encoding in
+  union
+    [
+      case (Tag 0)
+        (obj2
+           (req "error" (constant "cannot_parse_operation"))
+           (req "operation" Operation_hash.encoding))
+        (function Cannot_parse_operation operation -> Some ((), operation)
+                | _ -> None)
+        (fun ((), operation) -> Cannot_parse_operation operation) ;
+      case (Tag 1)
+        (obj3
+           (req "error" (constant "invalid_fitness"))
+           (req "expected" Fitness.encoding)
+           (req "found" Fitness.encoding))
+        (function
+          | Invalid_fitness { expected ; found } ->
+              Some ((), expected, found)
+          | _ -> None)
+        (fun ((), expected, found) -> Invalid_fitness { expected ; found }) ;
+      case (Tag 2)
+        (obj1
+           (req "error" (constant "non_increasing_timestamp")))
+        (function Non_increasing_timestamp -> Some ()
+                | _ -> None)
+        (fun () -> Non_increasing_timestamp) ;
+      case (Tag 3)
+        (obj1
+           (req "error" (constant "non_increasing_fitness")))
+        (function Non_increasing_fitness -> Some ()
+                | _ -> None)
+        (fun () -> Non_increasing_fitness) ;
+      case (Tag 4)
+        (obj3
+           (req "error" (constant "invalid_level"))
+           (req "expected" int32)
+           (req "found" int32))
+        (function
+          | Invalid_level { expected ; found } ->
+              Some ((), expected, found)
+          | _ -> None)
+        (fun ((), expected, found) -> Invalid_level { expected ; found }) ;
+      case (Tag 5)
+        (obj3
+           (req "error" (constant "invalid_proto_level"))
+           (req "expected" uint8)
+           (req "found" uint8))
+        (function
+          | Invalid_proto_level { expected ; found } ->
+              Some ((), expected, found)
+          | _ -> None)
+        (fun ((), expected, found) ->
+           Invalid_proto_level { expected ; found }) ;
+      case (Tag 6)
+        (obj2
+           (req "error" (constant "replayed_operation"))
+           (req "operation" Operation_hash.encoding))
+        (function Replayed_operation operation -> Some ((), operation)
+                | _ -> None)
+        (fun ((), operation) -> Replayed_operation operation) ;
+      case (Tag 7)
+        (obj3
+           (req "error" (constant "outdated_operation"))
+           (req "operation" Operation_hash.encoding)
+           (req "originating_block" Block_hash.encoding))
+        (function
+          | Outdated_operation { operation ; originating_block } ->
+              Some ((), operation, originating_block)
+          | _ -> None)
+        (fun ((), operation, originating_block) ->
+           Outdated_operation { operation ; originating_block }) ;
+      case (Tag 8)
+        (obj2
+           (req "error" (constant "unexpected_number_of_passes"))
+           (req "found" uint8))
+        (function
+          | Unexpected_number_of_validation_passes n -> Some ((), n)
+          | _ -> None)
+        (fun ((), n) -> Unexpected_number_of_validation_passes n) ;
+      case (Tag 9)
+        (obj4
+           (req "error" (constant "too_many_operations"))
+           (req "validation_pass" uint8)
+           (req "found" uint16)
+           (req "max" uint16))
+        (function
+          | Too_many_operations { pass ; found ; max } ->
+              Some ((), pass, found, max)
+          | _ -> None)
+        (fun ((), pass, found, max) ->
+           Too_many_operations { pass ; found ; max }) ;
+      case (Tag 10)
+        (obj4
+           (req "error" (constant "oversized_operation"))
+           (req "operation" Operation_hash.encoding)
+           (req "found" int31)
+           (req "max" int31))
+        (function
+          | Oversized_operation { operation ; size ; max } ->
+              Some ((), operation, size, max)
+          | _ -> None)
+        (fun ((), operation, size, max) ->
+           Oversized_operation { operation ; size ; max }) ;
+    ]
+
+let pp_block_error ppf = function
+  | Cannot_parse_operation oph ->
+      Format.fprintf ppf
+        "Failed to parse the operation %a."
+        Operation_hash.pp_short oph
+  | Invalid_fitness { expected ; found } ->
+      Format.fprintf ppf
+        "@[<v 2>Invalid fitness:@ \
+        \ expected %a@ \
+        \ found %a@]"
+        Fitness.pp expected
+        Fitness.pp found
+  | Non_increasing_timestamp ->
+      Format.fprintf ppf "Non increasing timestamp"
+  | Non_increasing_fitness ->
+      Format.fprintf ppf "Non increasing fitness"
+  | Invalid_level { expected ; found } ->
+      Format.fprintf ppf
+        "Invalid level:@ \
+        \ expected %ld@ \
+        \ found %ld"
+        expected
+        found
+  | Invalid_proto_level { expected ; found } ->
+      Format.fprintf ppf
+        "Invalid protocol level:@ \
+        \ expected %d@ \
+        \ found %d"
+        expected
+        found
+  | Replayed_operation oph ->
+      Format.fprintf ppf
+        "The operation %a was previously included in the chain."
+        Operation_hash.pp_short oph
+  | Outdated_operation { operation ; originating_block } ->
+      Format.fprintf ppf
+        "The operation %a is outdated (originated in block: %a)"
+        Operation_hash.pp_short operation
+        Block_hash.pp_short originating_block
+  | Expired_network { net_id ; expiration ; timestamp } ->
+      Format.fprintf ppf
+        "The block timestamp (%a) is later than \
+         its network expiration date: %a (net: %a)."
+        Time.pp_hum timestamp
+        Time.pp_hum expiration
+        Net_id.pp_short net_id
+  | Unexpected_number_of_validation_passes n ->
+      Format.fprintf ppf
+        "Invalid number of validation passes (found: %d)"
+        n
+  | Too_many_operations { pass ; found ; max } ->
+      Format.fprintf ppf
+        "Too many operations in validation pass %d (found: %d, max: %d)"
+        pass found max
+  | Oversized_operation { operation ; size ; max } ->
+      Format.fprintf ppf
+        "Oversized operation %a (size: %d, max: %d)"
+        Operation_hash.pp_short operation size max
+
+type error +=
+  | Invalid_block of
+      { block: Block_hash.t ; error: block_error }
+  | Unavailable_protocol of
+      { block: Block_hash.t ; protocol: Protocol_hash.t }
+  | Inconsistent_operations_hash of
+      { block: Block_hash.t ;
+        expected: Operation_list_list_hash.t ;
+        found: Operation_list_list_hash.t }
+
+let () =
+  Error_monad.register_error_kind
+    `Permanent
+    ~id:"validator.invalid_block"
+    ~title:"Invalid block"
+    ~description:"Invalid block."
+    ~pp:begin fun ppf (block, error) ->
+      Format.fprintf ppf
+        "@[<v 2>Invalid block %a@ %a@]"
+        Block_hash.pp_short block pp_block_error error
+    end
+    Data_encoding.(merge_objs
+                     (obj1 (req "invalid_block" Block_hash.encoding))
+                     block_error_encoding)
+    (function Invalid_block { block ; error } ->
+       Some (block, error) | _ -> None)
+    (fun (block, error) ->
+       Invalid_block { block ; error }) ;
+  Error_monad.register_error_kind
+    `Temporary
+    ~id:"validator.unavailable_protocol"
+    ~title:"Missing protocol"
+    ~description:"The protocol required for validating a block is missing."
+    ~pp:begin fun ppf (block, protocol) ->
+      Format.fprintf ppf
+        "Missing protocol (%a) when validating the block %a."
+        Protocol_hash.pp_short protocol
+        Block_hash.pp_short block
+    end
+    Data_encoding.(
+      obj2
+        (req "block" Block_hash.encoding)
+        (req "missing_protocol" Protocol_hash.encoding))
+    (function
+      | Unavailable_protocol { block ; protocol } ->
+          Some (block, protocol)
+      | _ -> None)
+    (fun (block, protocol) -> Unavailable_protocol { block ; protocol }) ;
+  Error_monad.register_error_kind
+    `Temporary
+    ~id:"validator.inconsistent_operations_hash"
+    ~title:"Invalid merkle tree"
+    ~description:"The provided list of operations is inconsistent with \
+                  the block header."
+    ~pp:begin fun ppf (block, expected, found) ->
+      Format.fprintf ppf
+        "@[<v 2>The provided list of operations for block %a \
+        \ is inconsistent with the block header@ \
+        \ expected: %a@ \
+        \ found: %a@]"
+        Block_hash.pp_short block
+        Operation_list_list_hash.pp_short expected
+        Operation_list_list_hash.pp_short found
+    end
+    Data_encoding.(
+      obj3
+        (req "block" Block_hash.encoding)
+        (req "expected" Operation_list_list_hash.encoding)
+        (req "found" Operation_list_list_hash.encoding))
+    (function
+      | Inconsistent_operations_hash { block ; expected ; found } ->
+          Some (block, expected, found)
+      | _ -> None)
+    (fun (block, expected, found) ->
+       Inconsistent_operations_hash { block ; expected ; found })
+
diff --git a/src/lib_node_shell_base/block_validator_errors.mli b/src/lib_node_shell_base/block_validator_errors.mli
new file mode 100644
index 000000000..3f946313a
--- /dev/null
+++ b/src/lib_node_shell_base/block_validator_errors.mli
@@ -0,0 +1,39 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+type block_error =
+  | Cannot_parse_operation of Operation_hash.t
+  | Invalid_fitness of { expected: Fitness.t ; found: Fitness.t }
+  | Non_increasing_timestamp
+  | Non_increasing_fitness
+  | Invalid_level of { expected: Int32.t ; found: Int32.t }
+  | Invalid_proto_level of { expected: int ; found: int }
+  | Replayed_operation of Operation_hash.t
+  | Outdated_operation of
+      { operation: Operation_hash.t;
+        originating_block: Block_hash.t }
+  | Expired_network of
+      { net_id: Net_id.t ;
+        expiration: Time.t ;
+        timestamp: Time.t ;
+      }
+  | Unexpected_number_of_validation_passes of int (* uint8 *)
+  | Too_many_operations of { pass: int; found: int; max: int }
+  | Oversized_operation of { operation: Operation_hash.t;
+                             size: int; max: int }
+
+type error +=
+  | Invalid_block of
+      { block: Block_hash.t ; error: block_error }
+  | Unavailable_protocol of
+      { block: Block_hash.t ; protocol: Protocol_hash.t }
+  | Inconsistent_operations_hash of
+      { block: Block_hash.t ;
+        expected: Operation_list_list_hash.t ;
+        found: Operation_list_list_hash.t }
diff --git a/src/lib_node_shell_base/block_validator_worker_state.ml b/src/lib_node_shell_base/block_validator_worker_state.ml
new file mode 100644
index 000000000..6bcb79e1a
--- /dev/null
+++ b/src/lib_node_shell_base/block_validator_worker_state.ml
@@ -0,0 +1,92 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+module Request = struct
+  type view = {
+    net_id : Net_id.t ;
+    block : Block_hash.t ;
+    peer : P2p_types.Peer_id.t option ;
+  }
+  let encoding =
+    let open Data_encoding in
+    conv
+      (fun { net_id ; block ; peer } -> (block, net_id, peer))
+      (fun (block, net_id, peer) -> { net_id ; block ; peer })
+      (obj3
+         (req "block" Block_hash.encoding)
+         (req "net_id" Net_id.encoding)
+         (opt "peer" P2p_types.Peer_id.encoding))
+
+  let pp ppf { net_id ; block ; peer } =
+    Format.fprintf ppf "Validation of %a (net: %a)"
+      Block_hash.pp block
+      Net_id.pp_short net_id ;
+    match peer with
+    | None -> ()
+    | Some peer ->
+        Format.fprintf ppf "from peer %a"
+          P2p_types.Peer_id.pp_short peer
+end
+
+module Event = struct
+  type t =
+    | Validation_success of Request.view * Worker_types.request_status
+    | Validation_failure of Request.view * Worker_types.request_status * error list
+    | Debug of string
+
+  let level req =
+    match req with
+    | Debug _ -> Logging.Debug
+    | Validation_success _
+    | Validation_failure _ -> Logging.Notice
+
+  let encoding error_encoding =
+    let open Data_encoding in
+    union
+      [ case (Tag 0)
+          (obj1 (req "message" string))
+          (function Debug msg -> Some msg | _ -> None)
+          (fun msg -> Debug msg) ;
+        case (Tag 1)
+          (obj2
+             (req "successful_validation" Request.encoding)
+             (req "status" Worker_types.request_status_encoding))
+          (function Validation_success (r, s) -> Some (r, s) | _ -> None)
+          (fun (r, s) -> Validation_success (r, s)) ;
+        case (Tag 2)
+          (obj3
+             (req "failed_validation" Request.encoding)
+             (req "status" Worker_types.request_status_encoding)
+             (dft "errors" error_encoding []))
+          (function Validation_failure (r, s, err) -> Some (r, s, err) | _ -> None)
+          (fun (r, s, err) -> Validation_failure (r, s, err)) ]
+
+  let pp ppf = function
+    | Debug msg -> Format.fprintf ppf "%s" msg
+    | Validation_success (req, { pushed ; treated ; completed }) ->
+        Format.fprintf ppf
+          "@[<v 2>Block %a succesfully validated@,\
+           Pushed: %a, Treated: %a, Completed: %a@]"
+          Block_hash.pp req.block
+          Time.pp_hum pushed Time.pp_hum treated Time.pp_hum completed
+    | Validation_failure (req, { pushed ; treated ; completed }, errs)->
+        Format.fprintf ppf
+          "@[<v 2>Validation of block %a failed@,\
+           Pushed: %a, Treated: %a, Completed: %a@,\
+           Error: %a@]"
+          Block_hash.pp req.block
+          Time.pp_hum pushed Time.pp_hum treated Time.pp_hum completed
+          Error_monad.pp_print_error errs
+end
+
+module Worker_state = struct
+  type view = unit
+  let encoding = Data_encoding.empty
+  let pp _ppf _view = ()
+end
diff --git a/src/lib_node_shell_base/block_validator_worker_state.mli b/src/lib_node_shell_base/block_validator_worker_state.mli
new file mode 100644
index 000000000..e297cce04
--- /dev/null
+++ b/src/lib_node_shell_base/block_validator_worker_state.mli
@@ -0,0 +1,34 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+module Request : sig
+  type view = {
+    net_id : Net_id.t ;
+    block : Block_hash.t ;
+    peer: P2p_types.Peer_id.t option ;
+  }
+  val encoding : view Data_encoding.encoding
+  val pp : Format.formatter -> view -> unit
+end
+
+module Event : sig
+  type t =
+    | Validation_success of Request.view * Worker_types.request_status
+    | Validation_failure of Request.view * Worker_types.request_status * error list
+    | Debug of string
+  val level : t -> Logging.level
+  val encoding : error list Data_encoding.encoding -> t Data_encoding.encoding
+  val pp : Format.formatter -> t -> unit
+end
+
+module Worker_state : sig
+  type view = unit
+  val encoding : view Data_encoding.encoding
+  val pp : Format.formatter -> view -> unit
+end