d_cfg_mgr.h 15.8 KB
Newer Older
1
// Copyright (C) 2013-2016 Internet Systems Consortium, Inc. ("ISC")
2
//
3 4 5
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
6

7 8 9
#ifndef D_CFG_MGR_H
#define D_CFG_MGR_H

10 11
#include <cc/data.h>
#include <exceptions/exceptions.h>
12
#include <dhcpsrv/parsers/dhcp_parsers.h>
13 14 15 16

#include <stdint.h>
#include <string>

17 18 19 20 21 22 23
// Undefine the macro OPTIONAL which is defined in some operating
// systems but conflicts with class constant is the context base class.

#ifdef OPTIONAL
#undef OPTIONAL
#endif

24
namespace isc {
25
namespace process {
26

27 28 29
/// @brief Defines a map of ConstElementPtrs keyed by name
typedef std::map<std::string, isc::data::ConstElementPtr> ElementMap;

30 31 32 33 34 35 36
/// @brief Exception thrown if the configuration manager encounters an error.
class DCfgMgrBaseError : public isc::Exception {
public:
    DCfgMgrBaseError(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) { };
};

37 38 39 40
class DCfgContextBase;
/// @brief Pointer to a configuration context.
typedef boost::shared_ptr<DCfgContextBase> DCfgContextBasePtr;

41 42 43 44 45 46 47 48
/// @brief Abstract class that implements a container for configuration context.
/// It provides a single enclosure for the storage of configuration parameters
/// and any other context specific information that needs to be accessible
/// during configuration parsing as well as to the application as a whole.
/// The base class supports storage for a small set of simple data types.
/// Derivations simply add additional storage as needed.  Note that this class
/// declares the pure virtual clone() method, its copy constructor is protected,
/// and its copy operator is inaccessible.  Derivations must supply an
49 50 51
/// implementation of clone that calls the base class copy constructor.
/// This allows the management class to perform context backup and restoration
/// without derivation specific knowledge using logic like
52 53 54 55 56 57 58 59 60 61
/// the following:
///
///    // Make a backup copy
///    DCfgContextBasePtr backup_copy(context_->clone());
///    :
///    // Restore from backup
///    context_ = backup_copy;
///
class DCfgContextBase {
public:
62
    /// @brief Indicator that a configuration parameter is optional.
63 64
    static const bool OPTIONAL = true;
    static const bool REQUIRED = false;
65

66 67 68 69 70 71 72 73 74 75 76 77
    /// @brief Constructor
    DCfgContextBase();

    /// @brief Destructor
    virtual ~DCfgContextBase();

    /// @brief Fetches the value for a given boolean configuration parameter
    /// from the context.
    ///
    /// @param name is the name of the parameter to retrieve.
    /// @param value is an output parameter in which to return the retrieved
    /// value.
78 79 80 81
    /// @param optional if true, the parameter is optional and the method
    /// will not throw if the parameter is not found in the context. The
    /// contents of the output parameter, value, will not be altered.
    /// It defaults to false if not specified.
82 83 84 85
    ///
    /// @return The parameter's element's position information if found,
    /// otherwise it returns isc::data::Element::ZERO_POSITION().
    ///
86
    /// @throw throws DhcpConfigError if the context does not contain the
87
    /// parameter and optional is false.
88 89
    const data::Element::Position&
    getParam(const std::string& name, bool& value, bool optional=false);
90 91 92 93 94 95 96

    /// @brief Fetches the value for a given uint32_t configuration parameter
    /// from the context.
    ///
    /// @param name is the name of the parameter to retrieve.
    /// @param value is an output parameter in which to return the retrieved
    /// value.
97 98 99
    /// @param optional if true, the parameter is optional and the method
    /// will not throw if the parameter is not found in the context. The
    /// contents of the output parameter, value, will not be altered.
100 101 102 103
    ///
    /// @return The parameter's element's position information if found,
    /// otherwise it returns isc::data::Element::ZERO_POSITION().
    ///
104
    /// @throw throws DhcpConfigError if the context does not contain the
105
    /// parameter and optional is false.
106 107
    const data::Element::Position&
    getParam(const std::string& name, uint32_t& value,
108
                 bool optional=false);
109 110 111 112 113 114 115

    /// @brief Fetches the value for a given string configuration parameter
    /// from the context.
    ///
    /// @param name is the name of the parameter to retrieve.
    /// @param value is an output parameter in which to return the retrieved
    /// value.
116 117 118
    /// @param optional if true, the parameter is optional and the method
    /// will not throw if the parameter is not found in the context. The
    /// contents of the output parameter, value, will not be altered.
119 120 121 122
    ///
    /// @return The parameter's element's position information if found,
    /// otherwise it returns isc::data::Element::ZERO_POSITION().
    ///
123
    /// @throw throws DhcpConfigError if the context does not contain the
124
    /// parameter and optional is false.
125 126
    const data::Element::Position&
    getParam(const std::string& name, std::string& value,
127
                  bool optional=false);
128 129 130 131 132

    /// @brief Fetches the Boolean Storage. Typically used for passing
    /// into parsers.
    ///
    /// @return returns a pointer to the Boolean Storage.
133
    isc::dhcp::BooleanStoragePtr getBooleanStorage() {
134 135 136 137 138 139 140
        return (boolean_values_);
    }

    /// @brief Fetches the uint32 Storage. Typically used for passing
    /// into parsers.
    ///
    /// @return returns a pointer to the uint32 Storage.
141
    isc::dhcp::Uint32StoragePtr getUint32Storage() {
142 143 144 145 146 147 148
        return (uint32_values_);
    }

    /// @brief Fetches the string Storage. Typically used for passing
    /// into parsers.
    ///
    /// @return returns a pointer to the string Storage.
149
    isc::dhcp::StringStoragePtr getStringStorage() {
150 151 152
        return (string_values_);
    }

153
    /// @brief Creates a clone of this context object.
154
    ///
155 156 157 158 159 160
    /// As mentioned in the the class brief, derivation must supply an
    /// implementation that initializes the base class storage as well as its
    /// own.  Typically the derivation's clone method would return the result
    /// of passing  "*this" into its own copy constructor:
    ///
    /// @code
161 162 163 164
    /// class DStubContext : public DCfgContextBase {
    /// public:
    ///  :
    ///     // Clone calls its own copy constructor
165 166
    ///     virtual DCfgContextBasePtr clone() {
    ///         return (DCfgContextBasePtr(new DStubContext(*this)));
167 168 169 170 171 172 173 174 175 176 177
    ///     }
    ///
    ///     // Note that the copy constructor calls the base class copy ctor
    ///     // then initializes its additional storage.
    ///     DStubContext(const DStubContext& rhs) : DCfgContextBase(rhs),
    ///         extra_values_(new Uint32Storage(*(rhs.extra_values_))) {
    ///     }
    ///  :
    ///    // Here's the derivation's additional storage.
    ///    isc::dhcp::Uint32StoragePtr extra_values_;
    ///  :
178
    /// @endcode
179
    ///
180 181
    /// @return returns a pointer to the new clone.
    virtual DCfgContextBasePtr clone() = 0;
182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200

protected:
    /// @brief Copy constructor for use by derivations in clone().
    DCfgContextBase(const DCfgContextBase& rhs);

private:
    /// @brief Private assignment operator to avoid potential for slicing.
    DCfgContextBase& operator=(const DCfgContextBase& rhs);

    /// @brief Storage for boolean parameters.
    isc::dhcp::BooleanStoragePtr boolean_values_;

    /// @brief Storage for uint32 parameters.
    isc::dhcp::Uint32StoragePtr uint32_values_;

    /// @brief Storage for string parameters.
    isc::dhcp::StringStoragePtr string_values_;
};

201
/// @brief Defines a sequence of Element IDs used to specify a parsing order.
202 203
typedef std::vector<std::string> ElementIdList;

204 205 206 207 208 209 210
/// @brief Configuration Manager
///
/// DCfgMgrBase is an abstract class that provides the mechanisms for managing
/// an application's configuration.  This includes services for parsing sets of
/// configuration values, storing the parsed information in its converted form,
/// and retrieving the information on demand.  It is intended to be the worker
/// class which is handed a set of configuration values to process by upper
211
/// application management layers.
212 213 214 215
///
/// The class presents a public method for receiving new configurations,
/// parseConfig.  This method coordinates the parsing effort as follows:
///
216
/// @code
217
///    make backup copy of configuration context
218 219 220 221 222 223 224 225 226 227
///    Split top-level configuration elements into to sets:
///      1. Set of scalar elements (strings, booleans, ints, etc..)
///      2. Set of object elements (maps, lists, etc...)
///    For each entry in the scalar set:
///        get derivation-specific parser for element
///        run parser
///        update context with parsed results
///        break on error
///
///    For each entry in the object set;
228 229 230 231 232 233 234
///        get derivation-specific parser for element
///        run parser
///        update context with parsed results
///        break on error
///
///    if an error occurred
///        restore configuration context from backup
235
/// @endcode
236
///
237 238 239
/// The above structuring ensures that global parameters are parsed first
/// making them available during subsequent object element parsing. The order
/// in which the object elements are processed is either:
240 241 242 243 244 245
///
///    1. Natural order presented by the configuration set
///    2. Specific order determined by a list of element ids
///
/// This allows a derivation to specify the order in which its elements are
/// parsed if there are dependencies between elements.
246
///
247 248 249 250 251
/// To parse a given element, its id is passed into createConfigParser,
/// which returns an instance of the appropriate parser.  This method is
/// abstract so the derivation's implementation determines the type of parser
/// created. This isolates the knowledge of specific element ids and which
/// application specific parsers to derivation.
252
///
253 254 255
/// Once the parser has been created, it is used to parse the data value
/// associated with the element id and update the context with the parsed
/// results.
256 257 258
///
/// In the event that an error occurs, parsing is halted and the
/// configuration context is restored from backup.
259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283
class DCfgMgrBase {
public:
    /// @brief Constructor
    ///
    /// @param context is a pointer to the configuration context the manager
    /// will use for storing parsed results.
    ///
    /// @throw throws DCfgMgrBaseError if context is null
    DCfgMgrBase(DCfgContextBasePtr context);

    /// @brief Destructor
    virtual ~DCfgMgrBase();

    /// @brief Acts as the receiver of new configurations and coordinates
    /// the parsing as described in the class brief.
    ///
    /// @param config_set is a set of configuration elements to parsed.
    ///
    /// @return an Element that contains the results of configuration composed
    /// of an integer status value (0 means successful, non-zero means failure),
    /// and a string explanation of the outcome.
    isc::data::ConstElementPtr parseConfig(isc::data::ConstElementPtr
                                           config_set);

    /// @brief Adds a given element id to the end of the parse order list.
284
    ///
285 286 287 288
    /// The order in which object elements are retrieved from this is the
    /// order in which they are added to the list. Derivations should use this
    /// method to populate the parse order as part of their constructor.
    /// Scalar parameters should NOT be included in this list.
289
    ///
290 291
    /// @param element_id is the string name of the element as it will appear
    /// in the configuration set.
292
    void addToParseOrder(const std::string& element_id){
293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309
        parse_order_.push_back(element_id);
    }

    /// @brief Fetches the parse order list.
    ///
    /// @return returns a const reference to the list.
    const ElementIdList& getParseOrder() const {
        return (parse_order_);
    }

    /// @brief Fetches the configuration context.
    ///
    /// @return returns a pointer reference to the configuration context.
    DCfgContextBasePtr& getContext() {
        return (context_);
    }

310 311 312 313 314 315 316 317 318 319
    /// @brief Returns configuration summary in the textual format.
    ///
    /// This method returns the brief text describing the current configuration.
    /// It may be used for logging purposes, e.g. whn the new configuration is
    /// committed to notify a user about the changes in configuration.
    ///
    /// @param selection Bitfield which describes the parts of the configuration
    /// to be returned.
    ///
    /// @return Summary of the configuration in the textual format.
320
    virtual std::string getConfigSummary(const uint32_t selection) = 0;
321

322
protected:
323 324 325 326 327 328 329 330 331 332 333 334 335 336
    /// @brief Parses a set of scalar configuration elements into global
    /// parameters
    ///
    /// For each scalar element in the set:
    ///  - create a parser for the element
    ///  - invoke the parser's build method
    ///  - invoke the parser's commit method
    ///
    /// This will commit the values to context storage making them accessible
    /// during object parsing.
    ///
    /// @param params_config set of scalar configuration elements to parse
    virtual void buildParams(isc::data::ConstElementPtr params_config);

337 338 339 340 341
    /// @brief  Create a parser instance based on an element id.
    ///
    /// Given an element_id returns an instance of the appropriate parser.
    /// This method is abstract, isolating any direct knowledge of element_ids
    /// and parsers to within the application-specific derivation.
342 343 344
    ///
    /// @param element_id is the string name of the element as it will appear
    /// in the configuration set.
345 346
    /// @param pos position within the configuration text (or file) of element
    /// to be parsed.  This is passed for error messaging.
347 348 349 350
    ///
    /// @return returns a ParserPtr to the parser instance.
    /// @throw throws DCfgMgrBaseError if an error occurs.
    virtual isc::dhcp::ParserPtr
351 352 353
    createConfigParser(const std::string& element_id,
                       const isc::data::Element::Position& pos
                       = isc::data::Element::Position()) = 0;
354

355 356
    /// @brief Abstract factory which creates a context instance.
    ///
357 358 359 360 361 362
    /// This method is used at the beginning of configuration process to
    /// create a fresh, empty copy of the derivation-specific context. This
    /// new context will be populated during the configuration process
    /// and will replace the existing context provided the configuration
    /// process completes without error.
    ///
363 364 365 366 367 368 369 370 371 372 373 374 375
    /// @return Returns a DCfgContextBasePtr to the new context instance.
    virtual DCfgContextBasePtr createNewContext() = 0;

    /// @brief Replaces existing context with a new, emtpy context.
    void resetContext();

    /// @brief Update the current context.
    ///
    /// Replaces the existing context with the given context.
    /// @param context Pointer to the new context.
    /// @throw DCfgMgrBaseError if context is NULL.
    void setContext(DCfgContextBasePtr& context);

376 377
private:

378 379 380
    /// @brief Parse a configuration element.
    ///
    /// Given an element_id and data value, instantiate the appropriate
381 382 383 384 385 386 387 388 389 390 391
    /// parser,  parse the data value, and commit the results.
    ///
    /// @param element_id is the string name of the element as it will appear
    /// in the configuration set.
    /// @param value is the data value to be parsed and associated with
    /// element_id.
    ///
    /// @throw throws DCfgMgrBaseError if an error occurs.
    void buildAndCommit(std::string& element_id,
                        isc::data::ConstElementPtr value);

392 393 394 395
    /// @brief A list of element ids which specifies the element parsing order.
    ///
    /// If the list is empty, the natural order in the configuration set
    /// it used.
396 397 398 399 400 401 402 403 404 405
    ElementIdList parse_order_;

    /// @brief Pointer to the configuration context instance.
    DCfgContextBasePtr context_;
};

/// @brief Defines a shared pointer to DCfgMgrBase.
typedef boost::shared_ptr<DCfgMgrBase> DCfgMgrBasePtr;


406
}; // end of isc::process namespace
407 408 409
}; // end of isc namespace

#endif // D_CFG_MGR_H