SERVER-26411 Move balancer sources under mongo/db/s

1 files changed, 289 insertions, 0 deletions

diff --git a/src/mongo/s/balancer_configuration.h b/src/mongo/s/balancer_configuration.h
new file mode 100644
index 00000000000..2f5370d162c
--- /dev/null
+++ b/src/mongo/s/balancer_configuration.h
@@ -0,0 +1,289 @@
+/**
+ *    Copyright (C) 2016 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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 Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <boost/date_time/posix_time/posix_time.hpp>
+#include <boost/optional.hpp>
+#include <cstdint>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/platform/atomic_word.h"
+#include "mongo/s/migration_secondary_throttle_options.h"
+#include "mongo/stdx/mutex.h"
+
+namespace mongo {
+
+class BSONObj;
+class MigrationSecondaryThrottleOptions;
+class OperationContext;
+class Status;
+template <typename T>
+class StatusWith;
+
+/**
+ * Utility class to parse the balancer settings document, which has the following format:
+ *
+ * balancer: {
+ *  stopped: <true|false>,
+ *  mode: <full|autoSplitOnly|off>,         // Only consulted if "stopped" is missing or false
+ *  activeWindow: { start: "<HH:MM>", stop: "<HH:MM>" }
+ * }
+ */
+class BalancerSettingsType {
+public:
+    // Supported balancer modes
+    enum BalancerMode {
+        kFull,           // Balancer will always try to keep the cluster even
+        kAutoSplitOnly,  // Only balance on auto splits
+        kOff,            // Balancer is completely off
+    };
+
+    // The key under which this setting is stored on the config server
+    static const char kKey[];
+
+    // String representation of the balancer modes
+    static const char* kBalancerModes[];
+
+    /**
+     * Constructs a settings object with the default values. To be used when no balancer settings
+     * have been specified.
+     */
+    static BalancerSettingsType createDefault();
+
+    /**
+     * Interprets the BSON content as balancer settings and extracts the respective values.
+     */
+    static StatusWith<BalancerSettingsType> fromBSON(const BSONObj& obj);
+
+    /**
+     * Returns whether the balancer is enabled.
+     */
+    BalancerMode getMode() const {
+        return _mode;
+    }
+
+    /**
+     * Returns true if either 'now' is in the balancing window or if no balancing window exists.
+     */
+    bool isTimeInBalancingWindow(const boost::posix_time::ptime& now) const;
+
+    /**
+     * Returns the secondary throttle options.
+     */
+    const MigrationSecondaryThrottleOptions& getSecondaryThrottle() const {
+        return _secondaryThrottle;
+    }
+
+    /**
+     * Returns whether the balancer should wait for deletions after each completed move.
+     */
+    bool waitForDelete() const {
+        return _waitForDelete;
+    }
+
+private:
+    BalancerSettingsType();
+
+    BalancerMode _mode{kFull};
+
+    boost::optional<boost::posix_time::ptime> _activeWindowStart;
+    boost::optional<boost::posix_time::ptime> _activeWindowStop;
+
+    MigrationSecondaryThrottleOptions _secondaryThrottle;
+
+    bool _waitForDelete{false};
+};
+
+/**
+ * Utility class to parse the chunk size settings document, which has the following format:
+ *
+ * chunksize: { value: <value in MB between 1 and 1024> }
+ */
+class ChunkSizeSettingsType {
+public:
+    // The key under which this setting is stored on the config server
+    static const char kKey[];
+
+    // Default value to use for the max chunk size if one is not specified in the balancer
+    // configuration
+    static const uint64_t kDefaultMaxChunkSizeBytes;
+
+    /**
+     * Constructs a settings object with the default values. To be used when no chunk size settings
+     * have been specified.
+     */
+    static ChunkSizeSettingsType createDefault();
+
+    /**
+     * Interprets the BSON content as chunk size settings and extracts the respective values.
+     */
+    static StatusWith<ChunkSizeSettingsType> fromBSON(const BSONObj& obj);
+
+    uint64_t getMaxChunkSizeBytes() const {
+        return _maxChunkSizeBytes;
+    }
+
+    /**
+     * Validates that the specified max chunk size value (in bytes) is allowed.
+     */
+    static bool checkMaxChunkSizeValid(uint64_t maxChunkSizeBytes);
+
+private:
+    ChunkSizeSettingsType();
+
+    uint64_t _maxChunkSizeBytes{kDefaultMaxChunkSizeBytes};
+};
+
+/**
+ * Utility class to parse the sharding autoSplit settings document, which has the following format:
+ *
+ * autosplit: { enabled: <true|false> }
+ */
+class AutoSplitSettingsType {
+public:
+    // The key under which this setting is stored on the config server
+    static const char kKey[];
+
+    /**
+     * Constructs a settings object with the default values. To be used when no AutoSplit settings
+     * have been specified.
+     */
+    static AutoSplitSettingsType createDefault();
+
+    /**
+     * Interprets the BSON content as autosplit settings and extracts the respective values
+     */
+    static StatusWith<AutoSplitSettingsType> fromBSON(const BSONObj& obj);
+
+    bool getShouldAutoSplit() const {
+        return _shouldAutoSplit;
+    }
+
+private:
+    AutoSplitSettingsType();
+
+    bool _shouldAutoSplit{true};
+};
+
+/**
+ * Contains settings, which control the behaviour of the balancer.
+ */
+class BalancerConfiguration {
+    MONGO_DISALLOW_COPYING(BalancerConfiguration);
+
+public:
+    /**
+     * Primes the balancer configuration with some default values. The effective settings may change
+     * at a later time after a call to refresh().
+     */
+    BalancerConfiguration();
+    ~BalancerConfiguration();
+
+    /**
+     * Non-blocking method, which checks whether the balancer is enabled (without checking for the
+     * balancing window).
+     */
+    BalancerSettingsType::BalancerMode getBalancerMode() const;
+
+    /**
+     * Synchronous method, which writes the balancer mode to the configuration data.
+     */
+    Status setBalancerMode(OperationContext* txn, BalancerSettingsType::BalancerMode mode);
+
+    /**
+     * Returns whether balancing is allowed based on both the enabled state of the balancer and the
+     * balancing window.
+     */
+    bool shouldBalance() const;
+    bool shouldBalanceForAutoSplit() const;
+
+    /**
+     * Returns the secondary throttle options for the balancer.
+     */
+    MigrationSecondaryThrottleOptions getSecondaryThrottle() const;
+
+    /**
+     * Returns whether the balancer should wait for deletion of orphaned chunk data at the end of
+     * each migration.
+     */
+    bool waitForDelete() const;
+
+    /**
+     * Returns the max chunk size after which a chunk would be considered jumbo.
+     */
+    uint64_t getMaxChunkSizeBytes() const {
+        return _maxChunkSizeBytes.loadRelaxed();
+    }
+
+    bool getShouldAutoSplit() const {
+        return _shouldAutoSplit.loadRelaxed();
+    }
+
+    /**
+     * Blocking method, which refreshes the balancer configuration from the settings in the
+     * config.settings collection. It will stop at the first bad configuration value and return an
+     * error indicating what failed. The value for the bad configuration and the ones after it will
+     * remain unchanged.
+     *
+     * This method is thread-safe but it doesn't make sense to be called from more than one thread
+     * at a time.
+     */
+    Status refreshAndCheck(OperationContext* txn);
+
+private:
+    /**
+     * Reloads the balancer configuration from the settings document. Fails if the settings document
+     * cannot be read, in which case the values will remain unchanged.
+     */
+    Status _refreshBalancerSettings(OperationContext* txn);
+
+    /**
+     * Reloads the chunk sizes configuration from the settings document. Fails if the settings
+     * document cannot be read or if any setting contains invalid value, in which case the offending
+     * value will remain unchanged.
+     */
+    Status _refreshChunkSizeSettings(OperationContext* txn);
+
+    /**
+     * Reloads the autosplit configuration from the settings document. Fails if the settings
+     * document cannot be read.
+     */
+    Status _refreshAutoSplitSettings(OperationContext* txn);
+
+    // The latest read balancer settings and a mutex to protect its swaps
+    mutable stdx::mutex _balancerSettingsMutex;
+    BalancerSettingsType _balancerSettings;
+
+    // Max chunk size after which a chunk would be considered jumbo and won't be moved. This value
+    // is read on the critical path after each write operation, that's why it is cached.
+    AtomicUInt64 _maxChunkSizeBytes;
+    AtomicBool _shouldAutoSplit;
+};
+
+}  // namespace mongo