wl#12653 A reference caching service

To call a service implementation one needs to:
1. query the registry to get a reference to the service needed
2. call the service via the reference
3. call the registry to release the reference

While #2 is very fast (just a function pointer call) #1 and #3 can be
expensive since they'd need to interact with the registry's global
structure in a read/write fashion.

Hence if the above sequence is to be repeated in a quick succession it'd
be beneficial to do steps #1 and #3 just once and aggregate as many #2
steps in a single sequence.

This will usually mean to cache the service reference received in #1 and
delay 3 for as much as possible.

But since there's an active reference held to the service implementation
until 3 is taken special handling is needed to make sure that:

The references are released at regular intervals so changes in the
registry
can become effective. There is a way to mark a service implementation
as "inactive" ("dying") so that until all of the active references to it
are released no new ones are possible.

All of the above is part of the current audit API machinery, but needs
to be isolated into a separate service suite and made generally
available to
all services.

This is what this worklog aims to implement.

RB#24806

Author: V S Murthy Sidagam

components/libminchassis/dynamic_loader.cc

@@ -1136,7 +1136,7 @@ bool mysql_dynamic_loader_imp::unload_do_lock_provided_services(
    */
   minimal_chassis::rwlock_scoped_lock lock =
       mysql_registry_imp::lock_registry_for_write();
-  return mysql_dynamic_loader_imp ::
+  return mysql_dynamic_loader_imp::
       unload_do_check_provided_services_reference_count(
           components_to_unload, dependency_graph, scheme_services);
 }
@@ -1157,7 +1157,7 @@ bool mysql_dynamic_loader_imp::unload_do_lock_provided_services(
   @retval false success
   @retval true failure
 */
-bool mysql_dynamic_loader_imp ::
+bool mysql_dynamic_loader_imp::
     unload_do_check_provided_services_reference_count(
         const std::vector<mysql_component *> &components_to_unload,
         const std::map<const void *, std::vector<mysql_component *>>

components/library_mysys/my_memory.cc

@@ -1,4 +1,4 @@
-/* Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2.0,
@@ -40,7 +40,6 @@
   } while (0)
 #endif /* HAVE_VALGRIND */
 
-#define MY_ZEROFILL 32 /* fill array with zero */
 #define HEADER_SIZE 32
 #define MAGIC 1234
 #define USER_TO_HEADER(P) ((my_memory_header *)(((char *)P) - HEADER_SIZE))

components/reference_cache/CMakeLists.txt

@@ -0,0 +1,28 @@
+# Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License, version 2.0,
+# as published by the Free Software Foundation.
+#
+# This program is also distributed with certain software (including
+# but not limited to OpenSSL) that is licensed under separate terms,
+# as designated in a particular file or component or in included license
+# documentation.  The authors of MySQL hereby grant you an additional
+# permission to link the program and your derivative works with the
+# separately licensed software that they have included with MySQL.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License, version 2.0, for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
+
+MYSQL_ADD_COMPONENT(reference_cache
+  component.cc
+  channel.cc
+  cache.cc
+  MODULE_ONLY
+  LINK_LIBRARIES library_mysys)

components/reference_cache/cache.cc

@@ -0,0 +1,141 @@
+/* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License, version 2.0,
+as published by the Free Software Foundation.
+
+This program is also distributed with certain software (including
+but not limited to OpenSSL) that is licensed under separate terms,
+as designated in a particular file or component or in included license
+documentation.  The authors of MySQL hereby grant you an additional
+permission to link the program and your derivative works with the
+separately licensed software that they have included with MySQL.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License, version 2.0, for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+#include "cache.h"
+#include <include/mysql/components/services/mysql_mutex.h>
+#include <cassert>
+#include <cstring>
+#include "channel.h"
+
+namespace reference_caching {
+cache_imp *cache_imp::create(channel_imp *channel,
+                             SERVICE_TYPE(registry) * registry) {
+  assert(channel != nullptr);
+  return new cache_imp(channel, registry);
+}
+
+bool cache_imp::destroy(cache_imp *cache) {
+  delete cache;
+  return false;
+}
+
+bool cache_imp::get(unsigned service_name_index, const my_h_service **out_ref) {
+  bool channel_is_valid = m_channel->is_valid();
+
+  if (m_cache && channel_is_valid) {
+    // cache hit
+    *out_ref = m_cache[service_name_index];
+    return false;
+  }
+
+  // cache miss
+  flush();
+
+  m_cache = (my_h_service **)my_malloc(
+      KEY_mem_reference_cache, m_service_names.size() * sizeof(my_h_service *),
+      MY_ZEROFILL);
+
+  my_service<SERVICE_TYPE(registry_query)> query("registry_query", m_registry);
+
+  unsigned offset = 0;
+  for (std::string service_name : m_service_names) {
+    std::set<my_h_service> cache_set;
+
+    my_h_service_iterator iter;
+    if (!query->create(service_name.c_str(), &iter)) {
+      while (!query->is_valid(iter)) {
+        const char *implementation_name;
+        my_h_service svc;
+
+        // can't get the name
+        if (query->get(iter, &implementation_name)) break;
+
+        // not the same service
+        if (strncmp(implementation_name, service_name.c_str(),
+                    service_name.length()))
+          break;
+
+        // not in the ignore list
+        if (m_ignore_list.find(implementation_name) != m_ignore_list.end())
+          continue;
+
+        // add the reference to the list
+        if (!m_registry->acquire(implementation_name, &svc)) {
+          auto res = cache_set.insert(svc);
+
+          /*
+            release the unused reference if it's a duplicate of a reference
+            already added
+          */
+          if (!res.second) m_registry->release(svc);
+        }
+
+        if (query->next(iter)) break;
+      }
+      query->release(iter);
+    } else {
+      // The service is not present in the registry.
+      continue;
+    }
+
+    my_h_service *cache_row = (my_h_service *)my_malloc(
+        KEY_mem_reference_cache, (cache_set.size() + 1) * sizeof(my_h_service),
+        MY_ZEROFILL);
+
+    my_h_service *cache_ptr = cache_row;
+    for (my_h_service ref : cache_set) *cache_ptr++ = ref;
+
+    if (offset == service_name_index) *out_ref = cache_row;
+
+    m_cache[offset++] = cache_row;
+  }
+  return false;
+}
+
+bool cache_imp::flush() {
+  if (m_cache) {
+    unsigned offset = 0;
+    for (auto service_name : m_service_names) {
+      my_h_service *cache_row = m_cache[offset];
+      if (cache_row) {
+        for (my_h_service *iter = cache_row; *iter; iter++)
+          m_registry->release(*iter);
+        my_free(cache_row);
+        m_cache[offset] = nullptr;
+      }
+      offset++;
+    }
+    my_free(m_cache);
+    m_cache = nullptr;
+  }
+  return false;
+}
+
+cache_imp::cache_imp(channel_imp *channel, SERVICE_TYPE(registry) * registry)
+    : m_channel{channel->ref()}, m_cache{nullptr}, m_registry{registry} {
+  m_service_names = channel->get_service_names();
+}
+
+cache_imp::~cache_imp() {
+  flush();
+  m_channel->unref();
+}
+}  // namespace reference_caching

components/reference_cache/cache.h

@@ -0,0 +1,63 @@
+/* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License, version 2.0,
+as published by the Free Software Foundation.
+
+This program is also distributed with certain software (including
+but not limited to OpenSSL) that is licensed under separate terms,
+as designated in a particular file or component or in included license
+documentation.  The authors of MySQL hereby grant you an additional
+permission to link the program and your derivative works with the
+separately licensed software that they have included with MySQL.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License, version 2.0, for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#include <mysql/components/my_service.h>
+#include <mysql/components/services/registry.h>
+#include <set>
+#include <string>
+#include <unordered_map>
+#include "cache_allocator.h"
+#include "reference_cache_common.h"
+
+namespace reference_caching {
+
+class channel_imp;
+
+class cache_imp : public Cache_malloced {
+ public: /* top level APIs */
+  static cache_imp *create(channel_imp *channel,
+                           SERVICE_TYPE(registry) * registry);
+  static bool destroy(cache_imp *cache);
+  bool get(unsigned service_name_index, const my_h_service **ref);
+  bool flush();
+
+ public: /* utility */
+  cache_imp(channel_imp *channel, SERVICE_TYPE(registry) * registry);
+  ~cache_imp();
+
+ private:
+  // disable copy constructors
+  cache_imp(const cache_imp &);
+  cache_imp &operator=(const cache_imp &);
+
+  channel_imp *m_channel;
+  /*
+    This is a opaque pointer handle used to store the acquired service
+    implementaions handles.
+  */
+  my_h_service **m_cache;
+  SERVICE_TYPE(registry) * m_registry;
+  service_names_set<> m_service_names;
+  service_names_set<> m_ignore_list;
+};
+
+}  // namespace reference_caching

components/reference_cache/cache_allocator.h

@@ -0,0 +1,38 @@
+/* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License, version 2.0,
+as published by the Free Software Foundation.
+
+This program is also distributed with certain software (including
+but not limited to OpenSSL) that is licensed under separate terms,
+as designated in a particular file or component or in included license
+documentation.  The authors of MySQL hereby grant you an additional
+permission to link the program and your derivative works with the
+separately licensed software that they have included with MySQL.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License, version 2.0, for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#include <mysql/components/library_mysys/component_malloc_allocator.h>
+
+#ifndef REFERENCE_CACHE_ALLOCATOR_H
+#define REFERENCE_CACHE_ALLOCATOR_H
+
+namespace reference_caching {
+
+class Cache_malloced {
+ public:
+  static void *operator new(std::size_t sz);
+  static void operator delete(void *ptr, std::size_t sz);
+};
+
+}  // namespace reference_caching
+
+#endif /* REFERENCE_CACHE_ALLOCATOR_H */