c/controller_backend: store last error in controller backend delta queue

Signed-off-by: Michal Maslanka <michal@redpanda.com>

src/v/cluster/controller_backend.cc

@@ -865,6 +865,11 @@ ss::future<> controller_backend::reconcile_ntp(deltas_t& deltas) {
                   it->delta.previous_replica_set);
 
                 it->retries++;
+                if (ec.category() == error_category()) {
+                    it->last_error = static_cast<errc>(ec.value());
+                } else {
+                    it->last_error = errc::partition_operation_failed;
+                }
                 stop = true;
                 continue;
             }
@@ -902,6 +907,7 @@ ss::future<> controller_backend::reconcile_ntp(deltas_t& deltas) {
               *it,
               std::current_exception());
             it->retries++;
+            it->last_error = errc::partition_operation_failed;
             stop = true;
             continue;
         }
@@ -1992,7 +1998,13 @@ controller_backend::list_ntp_deltas(const model::ntp& ntp) const {
 
 std::ostream&
 operator<<(std::ostream& o, const controller_backend::delta_metadata& m) {
-    fmt::print(o, "{{delta: {}, retries: {}}}", m.delta, m.retries);
+    fmt::print(
+      o,
+      "{{delta: {}, retries: {}, last_error: {}({})}}",
+      m.delta,
+      m.retries,
+      m.last_error,
+      error_category().message(static_cast<int>(m.last_error)));
     return o;
 }
 

src/v/cluster/controller_backend.h

@@ -11,6 +11,7 @@
 
 #pragma once
 
+#include "cluster/errc.h"
 #include "cluster/fwd.h"
 #include "cluster/topic_table.h"
 #include "cluster/types.h"
@@ -226,6 +227,7 @@ class controller_backend
 
         topic_table::delta delta;
         uint64_t retries = 0;
+        cluster::errc last_error = errc::waiting_for_recovery;
         friend std::ostream& operator<<(std::ostream&, const delta_metadata&);
     };