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class factory

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In Java it is possible to create an object by knowing its class name in
runtime. Replication strategies are created this way (I presume class
name comes from configuration somehow), so when I translated the code to
urchin I wrote replication_strategy_registry class to map a class name to
a factory function. Now I see that this is used in other places too (I
see that snitch class created in the same way), so instead of repeating
the same code for each class hierarchy that is created from its name in
origin this patch tries to introduce an infrastructure to do that easily.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
This commit is contained in:
Gleb Natapov
2015-04-14 19:40:50 +03:00
committed by Avi Kivity
parent 3d134a797e
commit d0a1e35a86
4 changed files with 61 additions and 34 deletions
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19
locator/abstract_replication_strategy.cc
View File

@@ -3,14 +3,15 @@
*/
#include "abstract_replication_strategy.hh"
#include "utils/class_registrator.hh"
namespace locator {
abstract_replication_strategy::abstract_replication_strategy(const sstring& ks_name, token_metadata& token_metadata, std::unordered_map<sstring, sstring>& config_options) :
_ks_name(ks_name), _config_options(config_options), _token_metadata(token_metadata) {}
std::unique_ptr<abstract_replication_strategy> abstract_replication_strategy::create_replication_strategy(const sstring& ks_name, const sstring& strategy_name, token_metadata& token_metadata, std::unordered_map<sstring, sstring>& config_options) {
return replication_strategy_registry::create(strategy_name, ks_name, token_metadata, config_options);
std::unique_ptr<abstract_replication_strategy> abstract_replication_strategy::create_replication_strategy(const sstring& ks_name, const sstring& strategy_name, token_metadata& tk_metadata, std::unordered_map<sstring, sstring>& config_options) {
return create_object<abstract_replication_strategy>(strategy_name, ks_name, tk_metadata, config_options);
}
std::vector<inet_address> abstract_replication_strategy::get_natural_endpoints(token& search_token) {
@@ -18,18 +19,4 @@ std::vector<inet_address> abstract_replication_strategy::get_natural_endpoints(t
return calculate_natural_endpoints(key_token);
}
std::unordered_map<sstring, strategy_creator_type> replication_strategy_registry::_strategies;
void replication_strategy_registry::register_strategy(sstring name, strategy_creator_type creator) {
_strategies.emplace(name, std::move(creator));
}
std::unique_ptr<abstract_replication_strategy> replication_strategy_registry::create(const sstring& name, const sstring& keyspace_name, token_metadata& token_metadata, std::unordered_map<sstring, sstring>& config_options) {
return _strategies[name](keyspace_name, token_metadata, config_options);
}
replication_strategy_registrator::replication_strategy_registrator(sstring name, strategy_creator_type creator) {
replication_strategy_registry::register_strategy(name, creator);
}
}

14
locator/abstract_replication_strategy.hh
View File

@@ -33,18 +33,4 @@ public:
std::vector<inet_address> get_natural_endpoints(token& search_token);
};
using strategy_creator_type = std::function<std::unique_ptr<abstract_replication_strategy>(const sstring&, token_metadata&, std::unordered_map<sstring, sstring>&)>;
class replication_strategy_registry {
static std::unordered_map<sstring, strategy_creator_type> _strategies;
public:
static void register_strategy(sstring name, strategy_creator_type creator);
static std::unique_ptr<abstract_replication_strategy> create(const sstring& name, const sstring& keyspace_name, token_metadata& token_metadata, std::unordered_map<sstring, sstring>& config_options);
};
class replication_strategy_registrator {
public:
explicit replication_strategy_registrator(sstring name, strategy_creator_type creator);
};
}

7
locator/simple_strategy.cc
View File

@@ -4,6 +4,7 @@
#include <algorithm>
#include "simple_strategy.hh"
#include "utils/class_registrator.hh"
namespace locator {
@@ -45,9 +46,7 @@ size_t simple_strategy::get_replication_factor() const {
return std::stol(it->second);
}
static replication_strategy_registrator registerator("org.apache.cassandra.locator.SimpleStrategy",
[] (const sstring& keyspace_name, token_metadata& token_metadata, std::unordered_map<sstring, sstring>& config_options) {
return std::make_unique<simple_strategy>(keyspace_name, token_metadata, config_options);
});
using registry = class_registrator<abstract_replication_strategy, simple_strategy, const sstring&, token_metadata&, std::unordered_map<sstring, sstring>&>;
static registry registrator("org.apache.cassandra.locator.SimpleStrategy");
}