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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* @class storage::NodeStateUpdater
* @ingroup common
*
* @brief Interface to implement for handler of state updates
*
* This component is responsible for keeping the node and system state, and
* make it available to all components that want to access it. For thread
* safety it returns shared pointers to states, such that state objects
* retrieved are still valid after changes.
*
* If you're using the state so much that copying the shared pointer is too
* much, you can instead add yourself as a state listener, and keep your own
* copy of the state.
*
* When you set a new reported state, pending get node state requests will be
* answered, so do all your updates in one call.
*
* This interface exist so the storage server interface is not implementation
* dependent, and such that the state updater can be easily faked in tests.
*
*/
#pragma once
#include <string>
#include <vespa/vdslib/state/nodestate.h>
#include <vespa/vdslib/state/clusterstate.h>
namespace storage {
struct StateListener {
virtual ~StateListener() {}
virtual void handleNewState() = 0;
};
struct NodeStateUpdater {
typedef std::unique_ptr<NodeStateUpdater> UP;
virtual ~NodeStateUpdater() {}
virtual lib::NodeState::CSP getReportedNodeState() const = 0;
virtual lib::NodeState::CSP getCurrentNodeState() const = 0;
virtual lib::ClusterState::CSP getSystemState() const = 0;
virtual void addStateListener(StateListener&) = 0;
virtual void removeStateListener(StateListener&) = 0;
/**
* Multiple components typically request state, changes something and sets
* it back. To prevent race conditions here, they should grab this lock
* before altering the state.
*/
struct Lock {
typedef std::shared_ptr<Lock> SP;
virtual ~Lock() {}
};
virtual Lock::SP grabStateChangeLock() = 0;
/**
* Sets the node state. Remember that other components might be setting
* parts of the node state you don't care about. Thus, when you alter the
* nodestate, first retrieve it and only change the parts you want to.
*/
virtual void setReportedNodeState(const lib::NodeState& state) = 0;
};
} // storage
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