Implement iterator to go through expiration events

Ordered by deadline.

qclient @ 0ef4113c

-Subproject commit 18af58123af20bef3578b0f314e6cd4a638c5eb4
+Subproject commit 0ef4113c8902d5b79893989a0eaef3354ac79e69

src/CMakeLists.txt

@@ -63,6 +63,7 @@ add_library(XrdQuarkDB SHARED
   redis/Transaction.cc                redis/Transaction.hh
 
   storage/ConsistencyScanner.cc       storage/ConsistencyScanner.hh
+  storage/ExpirationEventIterator.cc  storage/ExpirationEventIterator.hh
   storage/KeyConstants.cc             storage/KeyConstants.hh
                                       storage/KeyDescriptor.hh
   storage/KeyDescriptorBuilder.cc     storage/KeyDescriptorBuilder.hh

src/storage/ExpirationEventIterator.cc

+// ----------------------------------------------------------------------
+// File: ExpirationEventIterator.cc
+// Author: Georgios Bitzes - CERN
+// ----------------------------------------------------------------------
+
+/************************************************************************
+ * quarkdb - a redis-like highly available key-value store              *
+ * Copyright (C) 2018 CERN/Switzerland                                  *
+ *                                                                      *
+ * This program is free software: you can redistribute it and/or modify *
+ * it under the terms of the GNU General Public License as published by *
+ * the Free Software Foundation, either version 3 of the License, or    *
+ * (at your option) any later version.                                  *
+ *                                                                      *
+ * 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 for more details.                         *
+ *                                                                      *
+ * You should have received a copy of the GNU General Public License    *
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.*
+ ************************************************************************/
+
+#include "ExpirationEventIterator.hh"
+#include "StagingArea.hh"
+#include "KeyLocators.hh"
+#include "../utils/IntToBinaryString.hh"
+
+using namespace quarkdb;
+
+ExpirationEventIterator::ExpirationEventIterator(StagingArea &st)
+: stagingArea(st), iter(stagingArea.getIterator()) {
+
+  std::string searchPrefix(1, char(InternalKeyType::kExpirationEvent));
+  iter->Seek(searchPrefix);
+  assertDeadlineSanity();
+}
+
+ExpirationEventIterator::~ExpirationEventIterator() {
+
+}
+
+bool ExpirationEventIterator::valid() {
+  if(!iter) return false;
+  if(!iter->Valid()) {
+    iter.reset();
+    return false;
+  }
+
+  if(iter->key()[0] != char(InternalKeyType::kExpirationEvent)) {
+    iter.reset();
+    return false;
+  }
+
+  return true;
+}
+
+void ExpirationEventIterator::next() {
+  iter->Next();
+  assertDeadlineSanity();
+}
+
+void ExpirationEventIterator::assertDeadlineSanity() {
+  if(valid()) {
+    ClockValue deadline = getDeadline();
+    qdb_assert(lastDeadline <= deadline);
+    lastDeadline = deadline;
+  }
+}
+
+ClockValue ExpirationEventIterator::getDeadline() {
+  return binaryStringToUnsignedInt(iter->key().data()+1);
+}
+
+std::string_view ExpirationEventIterator::getRedisKey() {
+  constexpr size_t offset = 1 + sizeof(ClockValue);
+  return std::string_view(iter->key().data()+offset, iter->key().size()-offset);
+}

src/storage/ExpirationEventIterator.hh

+// ----------------------------------------------------------------------
+// File: ExpirationEventIterator.hh
+// Author: Georgios Bitzes - CERN
+// ----------------------------------------------------------------------
+
+/************************************************************************
+ * quarkdb - a redis-like highly available key-value store              *
+ * Copyright (C) 2018 CERN/Switzerland                                  *
+ *                                                                      *
+ * This program is free software: you can redistribute it and/or modify *
+ * it under the terms of the GNU General Public License as published by *
+ * the Free Software Foundation, either version 3 of the License, or    *
+ * (at your option) any later version.                                  *
+ *                                                                      *
+ * 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 for more details.                         *
+ *                                                                      *
+ * You should have received a copy of the GNU General Public License    *
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.*
+ ************************************************************************/
+
+#ifndef QUARKDB_EXPIRATION_EVENT_ITERATOR_H
+#define QUARKDB_EXPIRATION_EVENT_ITERATOR_H
+
+#include <vector>
+#include <string_view>
+#include "../StateMachine.hh"
+
+namespace quarkdb {
+
+class StagingArea;
+using ClockValue = uint64_t;
+
+class ExpirationEventIterator {
+public:
+  ExpirationEventIterator(StagingArea &stagingArea);
+  virtual ~ExpirationEventIterator();
+
+  bool valid();
+  void next();
+
+  ClockValue getDeadline();
+  std::string_view getRedisKey();
+
+private:
+  void assertDeadlineSanity();
+
+  StagingArea &stagingArea;
+  ClockValue lastDeadline = 0;
+  StateMachine::IteratorPtr iter;
+
+};
+
+}
+
+#endif

test/state-machine.cc

@@ -25,6 +25,7 @@
 #include "storage/StagingArea.hh"
 #include "storage/ReverseLocator.hh"
 #include "storage/PatternMatching.hh"
+#include "storage/ExpirationEventIterator.hh"
 #include "StateMachine.hh"
 #include "test-utils.hh"
 #include <gtest/gtest.h>
@@ -699,6 +700,13 @@ TEST_F(State_Machine, Leases) {
   stateMachine()->getClock(clk);
   ASSERT_EQ(clk, 0u);
 
+  {
+    StagingArea stagingArea(*stateMachine());
+    ExpirationEventIterator iterator(stagingArea);
+    ASSERT_FALSE(iterator.valid());
+  }
+
+
   bool acquired;
   ASSERT_OK(stateMachine()->lease_acquire("my-lease", "some-string", ClockValue(1), 10, acquired));
   ASSERT_TRUE(acquired);
@@ -706,17 +714,55 @@ TEST_F(State_Machine, Leases) {
   stateMachine()->getClock(clk);
   ASSERT_EQ(clk, 1u);
 
+  {
+    StagingArea stagingArea(*stateMachine());
+    ExpirationEventIterator iterator(stagingArea);
+    ASSERT_TRUE(iterator.valid());
+    ASSERT_EQ(iterator.getDeadline(), 11u);
+    ASSERT_EQ(iterator.getRedisKey(), "my-lease");
+    iterator.next();
+    ASSERT_FALSE(iterator.valid());
+  }
+
   ASSERT_OK(stateMachine()->lease_acquire("my-lease", "some-string", ClockValue(9), 10, acquired));
   ASSERT_TRUE(acquired);
 
   stateMachine()->getClock(clk);
   ASSERT_EQ(clk, 9u);
 
+  {
+    StagingArea stagingArea(*stateMachine());
+    ExpirationEventIterator iterator(stagingArea);
+    ASSERT_TRUE(iterator.valid());
+    ASSERT_EQ(iterator.getDeadline(), 19u);
+    ASSERT_EQ(iterator.getRedisKey(), "my-lease");
+    iterator.next();
+    ASSERT_FALSE(iterator.valid());
+  }
+
   stateMachine()->lease_acquire("my-lease", "some-other-string", ClockValue(12), 10, acquired);
   ASSERT_FALSE(acquired);
 
   stateMachine()->getClock(clk);
   ASSERT_EQ(clk, 12u);
+
+  stateMachine()->lease_acquire("my-lease-2", "some-other-string", ClockValue(13), 10, acquired);
+  ASSERT_TRUE(acquired);
+
+  {
+    StagingArea stagingArea(*stateMachine());
+    ExpirationEventIterator iterator(stagingArea);
+    ASSERT_TRUE(iterator.valid());
+    ASSERT_EQ(iterator.getDeadline(), 19u);
+    ASSERT_EQ(iterator.getRedisKey(), "my-lease");
+    iterator.next();
+    ASSERT_TRUE(iterator.valid());
+    ASSERT_EQ(iterator.getDeadline(), 23u);
+    ASSERT_EQ(iterator.getRedisKey(), "my-lease-2");
+    iterator.next();
+    ASSERT_FALSE(iterator.valid());
+  }
+
 }
 
 static std::string sliceToString(const rocksdb::Slice &slice) {