From 30258bc14d44dc221eb88dda4fba03d1dc476305 Mon Sep 17 00:00:00 2001
From: Radoslaw Zarzynski <rzarzyns@redhat.com>
Date: Thu, 30 Jul 2020 16:46:17 +0200
Subject: [PATCH] crimson/tests: implement randomized testing for backfill.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
---
 src/test/crimson/test_backfill.cc | 96 ++++++++++++++++++++++++++++++-
 1 file changed, 95 insertions(+), 1 deletion(-)

diff --git a/src/test/crimson/test_backfill.cc b/src/test/crimson/test_backfill.cc
index bfd95ae3c1768..0409d47253d24 100644
--- a/src/test/crimson/test_backfill.cc
+++ b/src/test/crimson/test_backfill.cc
@@ -1,5 +1,7 @@
 #include <algorithm>
+#include <cstdlib>
 #include <deque>
+#include <functional>
 #include <initializer_list>
 #include <iostream>
 #include <iterator>
@@ -44,6 +46,13 @@ struct FakeStore {
     objs[obj] = version;
   }
 
+  void drop(const hobject_t& obj, const eversion_t version) {
+    auto it = objs.find(obj);
+    ceph_assert(it != std::end(objs));
+    ceph_assert(it->second == version);
+    objs.erase(it);
+  }
+
   template <class Func>
   hobject_t list(const hobject_t& start, Func&& per_entry) const {
     auto it = objs.lower_bound(start);
@@ -141,6 +150,12 @@ public:
     }
   }
 
+  void next_till_done() {
+    while (!events_to_dispatch.empty()) {
+      next_round();
+    }
+  }
+
   bool all_stores_look_like(const FakeStore& reference) const {
     const bool all_replica_match = std::all_of(
       std::begin(backfill_targets), std::end(backfill_targets),
@@ -279,7 +294,7 @@ void BackfillFixture::enqueue_drop(
   const hobject_t& obj,
   const eversion_t& v)
 {
-  std::cout << __func__ << std::endl;
+  backfill_targets.at(target).store.drop(obj, v);
 }
 
 void BackfillFixture::update_peers_last_backfill(
@@ -360,3 +375,82 @@ TEST(backfill, single_empty_replica)
   cluster_fixture.next_round();
   EXPECT_TRUE(cluster_fixture.all_stores_look_like(reference_store));
 }
+
+namespace StoreRandomizer {
+  // FIXME: copied & pasted from test/test_snap_mapper.cc. We need to
+  // find a way to avoid code duplication in test. A static library?
+  std::string random_string(std::size_t size) {
+    std::string name;
+    for (size_t j = 0; j < size; ++j) {
+      name.push_back('a' + (std::rand() % 26));
+    }
+    return name;
+  }
+
+  hobject_t random_hobject() {
+    uint32_t mask{0};
+    uint32_t bits{0};
+    return hobject_t(
+      random_string(1+(std::rand() % 16)),
+      random_string(1+(std::rand() % 16)),
+      snapid_t(std::rand() % 1000),
+      (std::rand() & ((~0)<<bits)) | (mask & ~((~0)<<bits)),
+      0, random_string(std::rand() % 16));
+  }
+
+  eversion_t random_eversion() {
+    return eversion_t{ std::rand() % 512U, std::rand() % 256UL };
+  }
+
+  FakeStore create() {
+    FakeStore store;
+    for (std::size_t i = std::rand() % 2048; i > 0; --i) {
+      store.push(random_hobject(), random_eversion());
+    }
+    return store;
+  }
+
+  template <class... Args>
+  void execute_random(Args&&... args) {
+    std::array<std::function<void()>, sizeof...(Args)> funcs = {
+      std::forward<Args>(args)...
+    };
+    return std::move(funcs[std::rand() % std::size(funcs)])();
+  }
+
+  FakeStore mutate(const FakeStore& source_store) {
+    FakeStore mutated_store;
+    source_store.list(hobject_t{}, [&] (const auto& kv) {
+      const auto& [ oid, version ] = kv;
+      execute_random(
+        []  { /* just drop the entry */ },
+        [&] { mutated_store.push(oid, version); },
+        [&] { mutated_store.push(oid, random_eversion()); },
+        [&] { mutated_store.push(random_hobject(), version); },
+        [&] {
+          for (auto how_many = std::rand() % 8; how_many > 0; --how_many) {
+            mutated_store.push(random_hobject(), random_eversion());
+          }
+        }
+      );
+    });
+    return mutated_store;
+  }
+}
+
+// The name might suggest randomness is involved here. Well, that's true
+// but till we know the seed the test still is repeatable.
+TEST(backfill, one_pseudorandomized_replica)
+{
+  const auto reference_store = StoreRandomizer::create();
+  auto cluster_fixture = BackfillFixtureBuilder::add_source(
+    reference_store.objs
+  ).add_target(
+    StoreRandomizer::mutate(reference_store).objs
+  ).get_result();
+
+  EXPECT_CALL(cluster_fixture, backfilled);
+  cluster_fixture.next_till_done();
+
+  EXPECT_TRUE(cluster_fixture.all_stores_look_like(reference_store));
+}
-- 
2.39.5