Add active hosts manager for balance in the future. (vesoft-inc#304)

* Add active hosts manager for balance in the future.

* Address dutor's and sherman's comments

src/meta/ActiveHostsMan.h

@@ -0,0 +1,101 @@
+/* Copyright (c) 2018 - present, VE Software Inc. All rights reserved
+ *
+ * This source code is licensed under Apache 2.0 License
+ *  (found in the LICENSE.Apache file in the root directory)
+ */
+
+#ifndef META_ACTIVEHOSTSMAN_H_
+#define META_ACTIVEHOSTSMAN_H_
+
+#include "base/Base.h"
+#include <gtest/gtest_prod.h>
+#include "thread/GenericWorker.h"
+#include "time/TimeUtils.h"
+
+namespace nebula {
+namespace meta {
+
+struct HostInfo {
+    HostInfo() = default;
+    explicit HostInfo(int64_t lastHBTimeInSec)
+        : lastHBTimeInSec_(lastHBTimeInSec) {}
+
+    bool operator==(const HostInfo& that) const {
+        return this->lastHBTimeInSec_ == that.lastHBTimeInSec_;
+    }
+
+    bool operator!=(const HostInfo& that) const {
+        return !(*this == that);
+    }
+
+    int64_t lastHBTimeInSec_ = 0;
+};
+
+class ActiveHostsMan final {
+    FRIEND_TEST(ActiveHostsManTest, NormalTest);
+
+public:
+    ActiveHostsMan(int32_t intervalSeconds, int32_t expiredSeconds)
+        : intervalSeconds_(intervalSeconds)
+        , expirationInSeconds_(expiredSeconds) {
+        CHECK(checkThread_.start());
+        checkThread_.addTimerTask(intervalSeconds * 1000,
+                                  intervalSeconds * 1000,
+                                  &ActiveHostsMan::cleanExpiredHosts,
+                                  this);
+    }
+
+    ~ActiveHostsMan() {
+        checkThread_.stop();
+        checkThread_.wait();
+    }
+
+    void updateHostInfo(HostAddr hostAddr, HostInfo info) {
+        folly::RWSpinLock::ReadHolder rh(&lock_);
+        auto it = hostsMap_.find(hostAddr);
+        if (it == hostsMap_.end()) {
+            folly::RWSpinLock::UpgradedHolder uh(&lock_);
+            hostsMap_.emplace(std::move(hostAddr), std::move(info));
+        } else {
+            it->second.lastHBTimeInSec_ = info.lastHBTimeInSec_;
+        }
+    }
+
+    std::vector<HostAddr> getActiveHosts() {
+        std::vector<HostAddr> hosts;
+        folly::RWSpinLock::ReadHolder rh(&lock_);
+        hosts.resize(hostsMap_.size());
+        std::transform(hostsMap_.begin(), hostsMap_.end(), hosts.begin(),
+                       [](const auto& entry) -> decltype(auto) {
+            return entry.first;
+        });
+        return hosts;
+    }
+
+protected:
+    void cleanExpiredHosts() {
+        int64_t now = time::TimeUtils::nowInSeconds();
+        folly::RWSpinLock::WriteHolder rh(&lock_);
+        auto it = hostsMap_.begin();
+        while (it != hostsMap_.end()) {
+            if ((now - it->second.lastHBTimeInSec_) > expirationInSeconds_) {
+                LOG(INFO) << it->first << " expired! last hb time "
+                          << it->second.lastHBTimeInSec_;
+                it = hostsMap_.erase(it);
+            } else {
+                it++;
+            }
+        }
+    }
+
+private:
+    folly::RWSpinLock lock_;
+    std::unordered_map<HostAddr, HostInfo> hostsMap_;
+    thread::GenericWorker checkThread_;
+    int32_t intervalSeconds_ = 0;
+    int32_t expirationInSeconds_ = 5 * 60;
+};
+}  // namespace meta
+}  // namespace nebula
+
+#endif  // META_ACTIVEHOSTSMAN_H_

src/meta/test/ActiveHostsManTest.cpp

@@ -0,0 +1,47 @@
+/* Copyright (c) 2018 - present, VE Software Inc. All rights reserved
+ *
+ * This source code is licensed under Apache 2.0 License
+ *  (found in the LICENSE.Apache file in the root directory)
+ */
+#include "base/Base.h"
+#include <gtest/gtest.h>
+#include "meta/ActiveHostsMan.h"
+
+namespace nebula {
+namespace meta {
+
+TEST(ActiveHostsManTest, NormalTest) {
+    auto now = time::TimeUtils::nowInSeconds();
+    ActiveHostsMan ahMan(1, 1);
+    ahMan.updateHostInfo(HostAddr(0, 0), HostInfo(now));
+    ahMan.updateHostInfo(HostAddr(0, 1), HostInfo(now));
+    ahMan.updateHostInfo(HostAddr(0, 2), HostInfo(now));
+
+    ASSERT_EQ(3, ahMan.getActiveHosts().size());
+    ahMan.updateHostInfo(HostAddr(0, 0), HostInfo(now + 2));
+    ASSERT_EQ(3, ahMan.getActiveHosts().size());
+    {
+        folly::RWSpinLock::ReadHolder rh(&ahMan.lock_);
+        ASSERT_EQ(HostInfo(now + 2),  ahMan.hostsMap_[HostAddr(0, 0)]);
+    }
+
+    sleep(3);
+    ASSERT_EQ(1, ahMan.getActiveHosts().size());
+    {
+        folly::RWSpinLock::ReadHolder rh(&ahMan.lock_);
+        ASSERT_EQ(HostInfo(now + 2),  ahMan.hostsMap_[HostAddr(0, 0)]);
+    }
+}
+
+}  // namespace meta
+}  // namespace nebula
+
+
+int main(int argc, char** argv) {
+    testing::InitGoogleTest(&argc, argv);
+    folly::init(&argc, &argv, true);
+    google::SetStderrLogging(google::INFO);
+    return RUN_ALL_TESTS();
+}
+
+

src/meta/test/CMakeLists.txt

@@ -92,3 +92,19 @@ nebula_link_libraries(
 
 nebula_add_test(meta_client_test)
 
+add_executable(
+    active_hosts_man_test
+    ActiveHostsManTest.cpp
+    $<TARGET_OBJECTS:base_obj>
+    $<TARGET_OBJECTS:thread_obj>
+    $<TARGET_OBJECTS:time_obj>
+    $<TARGET_OBJECTS:fs_obj>
+    $<TARGET_OBJECTS:network_obj>
+)
+nebula_link_libraries(
+    active_hosts_man_test
+    gtest
+)
+
+nebula_add_test(active_hosts_man_test)
+