API for getting archived log files

Summary: Also expanded class LogFile to have startSequene and FileSize and exposed it publicly

Test Plan: make all check

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12087

include/leveldb/db.h

@@ -12,7 +12,7 @@
 #include "leveldb/iterator.h"
 #include "leveldb/options.h"
 #include "leveldb/types.h"
-#include "leveldb/transaction_log_iterator.h"
+#include "leveldb/transaction_log.h"
 
 namespace leveldb {
 
@@ -232,6 +232,14 @@ class DB {
   virtual Status GetLiveFiles(std::vector<std::string>&,
                               uint64_t* manifest_file_size) = 0;
 
+  // Retrieve the sorted list of all wal files with earliest file first
+  virtual Status GetSortedWalFiles(VectorLogPtr& files) = 0;
+
+  // Delete wal files in files. These can be either live or archived.
+  // Returns Status::OK if all files could be deleted, otherwise Status::IOError
+  // which contains information about files that could not be deleted.
+  virtual Status DeleteWalFiles(const VectorLogPtr& files) = 0;
+
   // The sequence number of the most recent transaction.
   virtual SequenceNumber GetLatestSequenceNumber() = 0;
 

include/leveldb/transaction_log.h

@@ -3,10 +3,46 @@
 #define STORAGE_LEVELDB_INCLUDE_TRANSACTION_LOG_ITERATOR_H_
 
 #include "leveldb/status.h"
+#include "leveldb/types.h"
 #include "leveldb/write_batch.h"
 
 namespace leveldb {
 
+class LogFile;
+typedef std::vector<std::unique_ptr<LogFile>> VectorLogPtr;
+
+enum  WalFileType {
+  /* Indicates that WAL file is in archive directory. WAL files are moved from
+   * the main db directory to archive directory once they are not live and stay
+   * there for a duration of WAL_ttl_seconds which can be set in Options
+   */
+  kArchivedLogFile = 0,
+
+  /* Indicates that WAL file is live and resides in the main db directory */
+  kAliveLogFile = 1
+} ;
+
+class LogFile {
+ public:
+  LogFile() {}
+  virtual ~LogFile() {}
+
+  // Returns log file's name excluding the db path
+  virtual std::string Filename() const = 0;
+
+  // Primary identifier for log file.
+  // This is directly proportional to creation time of the log file
+  virtual uint64_t LogNumber() const = 0;
+
+  // Log file can be either alive or archived
+  virtual WalFileType Type() const = 0;
+
+  // Starting sequence number of writebatch written in this log file
+  virtual SequenceNumber StartSequence() const = 0;
+
+  // Size of log file on disk in Bytes
+  virtual uint64_t SizeFileBytes() const = 0;
+};
 
 struct BatchResult {
   SequenceNumber sequence;

include/leveldb/types.h

@@ -7,7 +7,7 @@ namespace leveldb {
 
 // Define all public custom types here.
 
-//  Represents a sequence number in a WAL file.
+// Represents a sequence number in a WAL file.
 typedef uint64_t SequenceNumber;
 
 }  //  namespace leveldb

include/utilities/stackable_db.h

@@ -139,6 +139,15 @@ class StackableDB : public DB {
     return sdb_->GetLatestSequenceNumber();
   }
 
+  virtual Status GetSortedWalFiles(VectorLogPtr& files) override {
+    return sdb_->GetSortedWalFiles(files);
+  }
+
+  virtual Status DeleteWalFiles(const VectorLogPtr& files)
+    override{
+      return sdb_->DeleteWalFiles(files);
+  }
+
   virtual Status GetUpdatesSince(SequenceNumber seq_number,
                                  unique_ptr<TransactionLogIterator>* iter)
     override {