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wsrep-lib/include/wsrep/server_context.hpp
Teemu Ollakka 3456a8b953 Unit tests for identifier class.
2018-06-12 11:22:02 +03:00

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//
// Copyright (C) 2018 Codership Oy <info@codership.com>
//
/*! \file server_context.hpp
*
* Server Context Abstraction
* ==========================
*
* This file defines an interface for WSREP Server Context.
* The Server Context will encapsulate server identification,
* server state and server capabilities. The class also
* defines an interface for manipulating server state, applying
* of remote transaction write sets, processing SST requests,
* creating local client connections for local storage access
* operations.
*
* Concepts
* ========
*
* State Snapshot Transfer
* -----------------------
*
* Depending on SST type (physical or logical), the server storage
* engine initialization must be done before or after SST happens.
* In case of physical SST method (typically rsync, filesystem snapshot)
* the SST happens before the storage engine is initialized, in case
* of logical backup typically after the storage engine initialization.
*
* Rollback Mode
* -------------
*
* When High Prioity Transaction (HTP) write set is applied, it
* may be required that the HTP Brute Force Aborts (BFA) locally
* executing transaction. As HTP must be able to apply all its
* write sets without interruption, the locally executing transaction
* must yield immediately, otherwise a transaction processing
* may stop or even deadlock. Depending on DBMS implementation,
* the local transaction may need to be rolled back immediately
* (synchronous mode) or the rollback may happen later on
* (asynchronous mode). The Server Context implementation
* which derives from Server Context base class must provide
* the base class the rollback mode which server operates on.
*
* ### Synchronous
*
* If the DBMS server implementation does not allow asynchronous rollback,
* the victim transaction must be rolled back immediately in order to
* allow transaction processing to proceed. Depending on DBMS process model,
* there may be either background thread which processes the rollback
* or the rollback can be done by the HTP applier.
*
* ### Asynchronous
*
* In asynchronous mode the BFA victim transaction is just marked
* to be aborted or in case of fully optimistic concurrency control,
* the conflict is detected at commit.
*
*/
#ifndef WSREP_SERVER_CONTEXT_HPP
#define WSREP_SERVER_CONTEXT_HPP
#include "mutex.hpp"
#include "condition_variable.hpp"
#include <vector>
#include <string>
namespace wsrep
{
// Forward declarations
class ws_handle;
class ws_meta;
class provider;
class client_context;
class transaction_context;
class gtid;
class view;
class data;
/*! \class Server Context
*
*
*/
class server_context
{
public:
/*!
* Server state enumeration.
*
* \todo Fix UML generation
*
* Server state diagram if the sst_before_init() returns false.
*
* [*] --> disconnected
* disconnected --> initializing
* initializing --> initialized
* initialized --> connected
* connected --> joiner
* joiner --> joined
* joined --> synced
* synced --> donor
* donor --> joined
*
* Server state diagram if the sst_before_init() returns true.
*
* [*] --> disconnected
* disconnected --> connected
* connected --> joiner
* joiner --> initializing
* initializing --> initialized
* initialized --> joined
* joined --> synced
* synced --> donor
* donor --> joined
*/
enum state
{
/*! Server is in disconnected state. */
s_disconnected,
/*! Server is initializing */
s_initializing,
/*! Server has been initialized */
s_initialized,
/*! Server is connected to the cluster */
s_connected,
/*! Server is receiving SST */
s_joiner,
/*! Server has received SST succesfully but has not synced
with rest of the cluster yet. */
s_joined,
/*! Server is donating state snapshot transfer */
s_donor,
/*! Server has synced with the cluster */
s_synced,
/*! Server is disconnecting from group */
s_disconnecting
};
static const int n_states_ = s_disconnecting + 1;
/*!
* Rollback Mode enumeration
*/
enum rollback_mode
{
/*! Asynchronous rollback mode */
rm_async,
/*! Synchronous rollback mode */
rm_sync
};
virtual ~server_context();
/*!
* Return human readable server name.
*
* \return Human readable server name string.
*/
const std::string& name() const { return name_; }
/*!
* Return Server identifier string.
*
* \return Server indetifier string.
*/
const std::string& id() const { return id_; }
/*!
* Return server group communication address.
*
* \return Return server group communication address.
*/
const std::string& address() const { return address_; }
/*!
* Return working directory
*
* \return String containing path to working directory.
*/
const std::string& working_dir() const { return working_dir_; }
/*!
* Get the rollback mode which server is operating in.
*
* \return Rollback mode.
*/
enum rollback_mode rollback_mode() const { return rollback_mode_; }
/*!
* Create client context which acts only locally, i.e. does
* not participate in replication. However, local client
* connection may execute transactions which require ordering,
* as when modifying local SR fragment storage requires
* strict commit ordering.
*
* \return Pointer to Client Context.
*/
virtual client_context* local_client_context() = 0;
/*!
* Load WSRep provider.
*
* \param provider WSRep provider library to be loaded.
* \param provider_options Provider specific options string
* to be passed for provider during initialization.
*
* \return Zero on success, non-zero on error.
*/
int load_provider(const std::string& provider,
const std::string& provider_options);
/*!
* Return reference to provider.
*
* \return Reference to provider
*
* \throw wsrep::runtime_error if provider has not been loaded
*/
virtual wsrep::provider& provider() const
{
if (provider_ == 0)
{
throw wsrep::runtime_error("provider not loaded");
}
return *provider_;
}
int connect(const std::string& cluster_name,
const std::string& cluster_address,
const std::string& state_donor,
bool bootstrap);
int disconnect();
/*!
* A method which will be called when the server
* has been joined to the cluster
*/
void on_connect();
/*!
* A method which will be called when a view
* notification event has been delivered by the
* provider.
*
* \params view wsrep::view object which holds the new view
* information.
*/
void on_view(const wsrep::view& view);
/*!
* A method which will be called when the server
* has been synchronized with the cluster.
*
* This will have a side effect of changing the Server Context
* state to s_synced.
*/
void on_sync();
/*!
* Wait until server reaches given state.
*/
void wait_until_state(wsrep::server_context::state) const;
/*!
* Virtual method to return true if the configured SST
* method requires SST to be performed before DBMS storage
* engine initialization, false otherwise.
*/
virtual bool sst_before_init() const = 0;
/*!
* Virtual method which will be called on *joiner* when the provider
* requests the SST request information. This method should
* provide a string containing an information which the donor
* server can use to donate SST.
*/
virtual std::string on_sst_required() = 0;
/*!
* Virtual method which will be called on *donor* when the
* SST request has been delivered by the provider.
* This method should initiate SST transfer or throw
* a wsrep::runtime_error
* if the SST transfer cannot be initiated. If the SST request
* initiation is succesful, the server remains in s_donor
* state until the SST is over or fails. The \param bypass
* should be passed to SST implementation. If the flag is true,
* no actual SST should happen, but the joiner server should
* be notified that the donor has seen the request. The notification
* should included \param gtid provided. This must be passed
* to sst_received() call on the joiner.
*
* \todo Figure out better exception for error codition.
*
* \param sst_request SST request string provided by the joiner.
* \param gtid GTID denoting the current replication position.
* \param bypass Boolean bypass flag.
*/
virtual void on_sst_request(const std::string& sst_request,
const wsrep::gtid& gtid,
bool bypass) = 0;
virtual void background_rollback(wsrep::client_context&) = 0;
/*!
*
*/
void sst_sent(const wsrep::gtid& gtid, int error);
/*!
* This method must be called by the joiner after the SST
* transfer has been received.
*
* \param gtid GTID provided by the SST transfer
*/
void sst_received(const wsrep::gtid& gtid, int error);
/*!
* This method must be called after the server initialization
* has been completed. The call has a side effect of changing
* the Server Context state to s_initialized.
*/
void initialized();
/*!
*
*/
/*!
* This method will be called by the provider hen
* a remote write set is being applied. It is the responsibility
* of the caller to set up transaction context and data properly.
*
* \todo Make this private, allow calls for provider implementations
* only.
* \param client_context Applier client context.
* \param transaction_context Transaction context.
* \param data Write set data
*
* \return Zero on success, non-zero on failure.
*/
int on_apply(wsrep::client_context& client_context,
const wsrep::ws_handle& ws_handle,
const wsrep::ws_meta& ws_meta,
const wsrep::data& data);
/*!
* This virtual method should be implemented by the DBMS
* to provide information if the current statement in processing
* is allowd for streaming replication.
*
* \return True if the statement is allowed for streaming
* replication, false otherwise.
*/
virtual bool statement_allowed_for_streaming(
const wsrep::client_context& client_context,
const wsrep::transaction_context& transaction_context) const;
void debug_log_level(int level) { debug_log_level_ = level; }
int debug_log_level() const { return debug_log_level_; }
protected:
/*! Server Context constructor
*
* \param mutex Mutex provided by the DBMS implementation.
* \param name Human Readable Server Name.
* \param id Server Identifier String, UUID or some unique
* identifier.
* \param address Server address in form of IPv4 address, IPv6 address
* or hostname.
* \param working_dir Working directory for replication specific
* data files.
* \param rollback_mode Rollback mode which server operates on.
*/
server_context(wsrep::mutex& mutex,
wsrep::condition_variable& cond,
const std::string& name,
const std::string& id,
const std::string& address,
const std::string& working_dir,
enum rollback_mode rollback_mode)
: mutex_(mutex)
, cond_(cond)
, state_(s_disconnected)
, state_waiters_(n_states_)
, provider_()
, name_(name)
, id_(id)
, address_(address)
, working_dir_(working_dir)
, rollback_mode_(rollback_mode)
, debug_log_level_(0)
{ }
private:
server_context(const server_context&);
server_context& operator=(const server_context&);
void state(wsrep::unique_lock<wsrep::mutex>&, enum state);
wsrep::mutex& mutex_;
wsrep::condition_variable& cond_;
enum state state_;
mutable std::vector<int> state_waiters_;
wsrep::provider* provider_;
std::string name_;
std::string id_;
std::string address_;
std::string working_dir_;
enum rollback_mode rollback_mode_;
int debug_log_level_;
};
static inline std::string to_string(enum wsrep::server_context::state state)
{
switch (state)
{
case wsrep::server_context::s_disconnected: return "disconnected";
case wsrep::server_context::s_initializing: return "initilizing";
case wsrep::server_context::s_initialized: return "initilized";
case wsrep::server_context::s_connected: return "connected";
case wsrep::server_context::s_joiner: return "joiner";
case wsrep::server_context::s_joined: return "joined";
case wsrep::server_context::s_donor: return "donor";
case wsrep::server_context::s_synced: return "synced";
case wsrep::server_context::s_disconnecting: return "disconnecting";
}
return "unknown";
}
}
#endif // WSREP_SERVER_CONTEXT_HPP
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