From fce48871bbf6a6ffb6c00edaffa817d4f2fbbf20 Mon Sep 17 00:00:00 2001
From: Eugen Zalinescu <eugen.zalinescu@nomadic-labs.com>
Date: Fri, 28 Jun 2024 16:00:09 +0200
Subject: [PATCH] DAL/Node: emit error when not able to fetch block in crawler

---
 src/bin_dal_node/crawler.ml | 35 +++++++++++++++++++++++++----------
 src/bin_dal_node/event.ml   | 17 +++++++++++++++++
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/src/bin_dal_node/crawler.ml b/src/bin_dal_node/crawler.ml
index c115c8683db3..935a081cce07 100644
--- a/src/bin_dal_node/crawler.ml
+++ b/src/bin_dal_node/crawler.ml
@@ -77,16 +77,31 @@ let finalized_heads_monitor ~name ~last_notified_level crawler_lib cctxt
       (* This block header is already notified or not targetted by the user. *)
       return acc
     else
-      let* pred_hash, _level =
-        get_predecessor crawler_lib hash shell_header.level
-      in
-      let* pred_shell_header =
-        fetch_tezos_shell_header cctxt headers_cache pred_hash
-      in
-      catch_up_if_needed
-        pred_hash
-        pred_shell_header
-        ((hash, shell_header) :: acc)
+      let*! res = get_predecessor crawler_lib hash shell_header.level in
+      match res with
+      | Error err ->
+          let*! () =
+            Event.(emit failed_to_fetch_block)
+              ("hash", Int32.pred shell_header.level, !last_notified_level, err)
+          in
+          return acc
+      | Ok (pred_hash, _level) -> (
+          let*! res = fetch_tezos_shell_header cctxt headers_cache pred_hash in
+          match res with
+          | Error err ->
+              let*! () =
+                Event.(emit failed_to_fetch_block)
+                  ( "hash",
+                    Int32.pred shell_header.level,
+                    !last_notified_level,
+                    err )
+              in
+              return acc
+          | Ok pred_shell_header ->
+              catch_up_if_needed
+                pred_hash
+                pred_shell_header
+                ((hash, shell_header) :: acc))
   in
   let process (hash, Block_header.{shell = shell_header; _}) =
     let shell_header_level = shell_header.level in
diff --git a/src/bin_dal_node/event.ml b/src/bin_dal_node/event.ml
index 15257aa41d07..bc3f169f805a 100644
--- a/src/bin_dal_node/event.ml
+++ b/src/bin_dal_node/event.ml
@@ -176,6 +176,23 @@ let daemon_error =
     ~pp1:Error_monad.pp_print_trace
     ("error", Error_monad.trace_encoding)
 
+let failed_to_fetch_block =
+  declare_4
+    ~section
+    ~name:"dal_node_crawler_failed_to_fetch_header"
+    ~msg:
+      "the crawler failed to fetch the block {type} at level {level} (for \
+       last_notified_level {last_notified}): {error}\n\
+       If you're a rollup producer or observer, you may be not be able to \
+       defend your rollup commitments involving DAL inputs in a refutation \
+       game."
+    ~level:Warning
+    ~pp4:Error_monad.pp_print_trace
+    ("type", Data_encoding.string)
+    ("level", Data_encoding.int32)
+    ("last_notified", Data_encoding.int32)
+    ("error", Error_monad.trace_encoding)
+
 let configuration_loaded =
   declare_0
     ~section
-- 
GitLab