From 491cc2a8dfcd117f6485b007de9badf31d1ceabd Mon Sep 17 00:00:00 2001
From: Piotr Dulikowski <piodul@scylladb.com>
Date: Wed, 29 Jun 2022 10:32:55 +0200
Subject: [PATCH] storage_proxy: don't rethrow exceptions from replicas when
 accounting read stats

Now, make_{data,mutation_data,digest}_requests don't rethrow the
exception received from replicas when increasing the error count metric.
---
 service/storage_proxy.cc | 42 +++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/service/storage_proxy.cc b/service/storage_proxy.cc
index 4a41ce1624..061b36f174 100644
--- a/service/storage_proxy.cc
+++ b/service/storage_proxy.cc
@@ -3749,16 +3749,24 @@ protected:
         for (const gms::inet_address& ep : boost::make_iterator_range(begin, end)) {
             // Waited on indirectly, shared_from_this keeps `this` alive
             (void)make_mutation_data_request(cmd, ep, timeout).then_wrapped([this, resolver, ep, start, exec = shared_from_this()] (future<rpc::tuple<foreign_ptr<lw_shared_ptr<reconcilable_result>>, cache_temperature>> f) {
+                std::exception_ptr ex;
                 try {
+                  if (!f.failed()) {
                     auto v = f.get0();
                     _cf->set_hit_rate(ep, std::get<1>(v));
                     resolver->add_mutate_data(ep, std::get<0>(std::move(v)));
                     ++_proxy->get_stats().mutation_data_read_completed.get_ep_stat(get_topology(), ep);
                     register_request_latency(latency_clock::now() - start);
-                } catch(...) {
-                    ++_proxy->get_stats().mutation_data_read_errors.get_ep_stat(get_topology(), ep);
-                    resolver->error(ep, std::current_exception());
+                    return;
+                  } else {
+                    ex = f.get_exception();
+                  }
+                } catch (...) {
+                  ex = std::current_exception();
                 }
+
+                ++_proxy->get_stats().mutation_data_read_errors.get_ep_stat(get_topology(), ep);
+                resolver->error(ep, std::move(ex));
             });
         }
     }
@@ -3767,17 +3775,25 @@ protected:
         for (const gms::inet_address& ep : boost::make_iterator_range(begin, end)) {
             // Waited on indirectly, shared_from_this keeps `this` alive
             (void)make_data_request(ep, timeout, want_digest).then_wrapped([this, resolver, ep, start, exec = shared_from_this()] (future<rpc::tuple<foreign_ptr<lw_shared_ptr<query::result>>, cache_temperature>> f) {
+                std::exception_ptr ex;
                 try {
+                  if (!f.failed()) {
                     auto v = f.get0();
                     _cf->set_hit_rate(ep, std::get<1>(v));
                     resolver->add_data(ep, std::get<0>(std::move(v)));
                     ++_proxy->get_stats().data_read_completed.get_ep_stat(get_topology(), ep);
                     _used_targets.push_back(ep);
                     register_request_latency(latency_clock::now() - start);
-                } catch(...) {
-                    ++_proxy->get_stats().data_read_errors.get_ep_stat(get_topology(), ep);
-                    resolver->error(ep, std::current_exception());
+                    return;
+                  } else {
+                    ex = f.get_exception();
+                  }
+                } catch (...) {
+                  ex = std::current_exception();
                 }
+
+                ++_proxy->get_stats().data_read_errors.get_ep_stat(get_topology(), ep);
+                resolver->error(ep, std::move(ex));
             });
         }
     }
@@ -3786,17 +3802,25 @@ protected:
         for (const gms::inet_address& ep : boost::make_iterator_range(begin, end)) {
             // Waited on indirectly, shared_from_this keeps `this` alive
             (void)make_digest_request(ep, timeout).then_wrapped([this, resolver, ep, start, exec = shared_from_this()] (future<rpc::tuple<query::result_digest, api::timestamp_type, cache_temperature>> f) {
+                std::exception_ptr ex;
                 try {
+                  if (!f.failed()) {
                     auto v = f.get0();
                     _cf->set_hit_rate(ep, std::get<2>(v));
                     resolver->add_digest(ep, std::get<0>(v), std::get<1>(v));
                     ++_proxy->get_stats().digest_read_completed.get_ep_stat(get_topology(), ep);
                     _used_targets.push_back(ep);
                     register_request_latency(latency_clock::now() - start);
-                } catch(...) {
-                    ++_proxy->get_stats().digest_read_errors.get_ep_stat(get_topology(), ep);
-                    resolver->error(ep, std::current_exception());
+                    return;
+                  } else {
+                    ex = f.get_exception();
+                  }
+                } catch (...) {
+                  ex = std::current_exception();
                 }
+
+                ++_proxy->get_stats().digest_read_errors.get_ep_stat(get_topology(), ep);
+                resolver->error(ep, std::move(ex));
             });
         }
     }