Add Exension and ExtensionFactory classes

include/rocksdb/extensions.h

@@ -0,0 +1,67 @@
+// An Env is an interface used by the rocksdb implementation to access
+// operating system functionality like the filesystem etc.  Callers
+// may wish to provide a custom Env object when opening a database to
+// get fine gain control; e.g., to rate limit file system operations.
+//
+// All Env implementations are safe for concurrent access from
+// multiple threads without any external synchronization.
+
+#ifndef STORAGE_ROCKSDB_INCLUDE_EXTENSION_H_
+#define STORAGE_ROCKSDB_INCLUDE_EXTENSION_H_
+
+#include <string>
+#include <vector>
+#include <unordered_map>
+#include "rocksdb/status.h"
+
+namespace rocksdb {
+  struct DBOptions;
+  struct ColumnFamilyOptions;
+
+  using std::unique_ptr;
+  using std::shared_ptr;
+
+
+  class Extension {
+  public:
+    virtual ~Extension() {}
+    // Names starting with "rocksdb." are reserved and should not be used
+    // by any clients of this package.
+    virtual const char* Name() const = 0;
+
+    // Sanitizes the specified DB Options and ColumnFamilyOptions.
+    //
+    // If the function cannot find a way to sanitize the input DB Options,
+    // a non-ok Status will be returned.
+    virtual Status SetOptions(const std::unordered_map<std::string, std::string> &,
+			      const DBOptions &,
+			      const ColumnFamilyOptions &) const {
+      return Status::OK();
+    }
+
+    // Return a string that contains printable format of table configurations.
+    // RocksDB prints configurations at DB Open().
+    virtual std::string GetPrintableTableOptions() const {
+      return "";
+    }
+
+    virtual Status GetOptionString(std::string* /*opt_string*/,
+				   const std::string& /*delimiter*/) const {
+      return Status::NotSupported(
+				  "The table factory doesn't implement GetOptionString().");
+    }
+
+  };
+
+  class EventListener;
+
+  class ExtensionFactory {
+  public:
+    virtual ~ExtensionFactory() { }
+    virtual Status LoadEventListener(const std::string & name, std::shared_ptr<EventListener> * ) {
+      return Status::NotFound("Event Listener not found", name);
+    }
+  };
+}  // namespace rocksdb
+
+#endif  // STORAGE_ROCKSDB_INCLUDE_EXTENSION_H_

include/rocksdb/listener.h

@@ -12,6 +12,7 @@
 #include <unordered_map>
 #include <vector>
 #include "rocksdb/compaction_job_stats.h"
+#include "rocksdb/extensions.h"
 #include "rocksdb/status.h"
 #include "rocksdb/table_properties.h"
 
@@ -285,7 +286,9 @@ struct ExternalFileIngestionInfo {
 // the current thread holding any DB mutex. This is to prevent potential
 // deadlock and performance issue when using EventListener callback
 // in a complex way.
-class EventListener {
+  class EventListener: public Extension {
+  public: // Methods from Extension
+    virtual const char * Name() const { return ""; }
  public:
   // A callback function to RocksDB which will be called whenever a
   // registered RocksDB flushes a file.  The default implementation is

include/rocksdb/table.h

@@ -24,6 +24,7 @@
 
 #include "rocksdb/cache.h"
 #include "rocksdb/env.h"
+#include "rocksdb/extensions.h"
 #include "rocksdb/iterator.h"
 #include "rocksdb/options.h"
 #include "rocksdb/status.h"
@@ -435,7 +436,7 @@ extern TableFactory* NewCuckooTableFactory(
 class RandomAccessFileReader;
 
 // A base class for table factories.
-class TableFactory {
+class TableFactory : public Extension {
  public:
   virtual ~TableFactory() {}