From 3d1e92b05aad8a7f997fb5e3adf2ac1faa13adb5 Mon Sep 17 00:00:00 2001
From: Dhruba Borthakur <dhruba@fb.com>
Date: Sun, 16 Dec 2012 21:01:02 -0800
Subject: [PATCH] Enhancements to rocksdb for better support for replication.

Summary:
1. The OpenForReadOnly() call should not lock the db. This is useful
so that multiple processes can open the same database concurrently
for reading.
2. GetUpdatesSince should not error out if the archive directory
does not exist.
3. A new constructor for WriteBatch that can takes a serialized
string as a parameter of the constructor.

Test Plan: make clean check

Reviewers: sheki

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7449
---
 .arcconfig                          |  7 +----
 db/db_impl.cc                       | 47 ++++++++++++++++-------------
 db/transaction_log_iterator_impl.cc |  4 +--
 include/leveldb/write_batch.h       |  5 ++-
 4 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/.arcconfig b/.arcconfig
index fe8c5aff7..8d6d65afb 100644
--- a/.arcconfig
+++ b/.arcconfig
@@ -1,10 +1,5 @@
 {
   "project_id" : "leveldb",
   "conduit_uri" : "https://reviews.facebook.net/",
-  "copyright_holder" : "",
-  "load" : [
-    "linters/src/"
-  ],
-  "lint_engine" : "FacebookFbcodeLintEngine", 
-  "lint.engine.single.linter" : "FbcodeCppLinter" 
+  "copyright_holder" : ""
 }
diff --git a/db/db_impl.cc b/db/db_impl.cc
index ff45962f7..700be1e8b 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -512,31 +512,33 @@ Status DBImpl::Recover(VersionEdit* edit, bool no_log_recory,
   // Ignore error from CreateDir since the creation of the DB is
   // committed only when the descriptor is created, and this directory
   // may already exist from a previous failed creation attempt.
-  env_->CreateDir(dbname_);
   assert(db_lock_ == NULL);
-  Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
-  if (!s.ok()) {
-    return s;
-  }
+  if (!no_log_recory) {
+    env_->CreateDir(dbname_);
+    Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
+    if (!s.ok()) {
+      return s;
+    }
 
-  if (!env_->FileExists(CurrentFileName(dbname_))) {
-    if (options_.create_if_missing) {
-      s = NewDB();
-      if (!s.ok()) {
-        return s;
+    if (!env_->FileExists(CurrentFileName(dbname_))) {
+      if (options_.create_if_missing) {
+        s = NewDB();
+        if (!s.ok()) {
+          return s;
+        }
+      } else {
+        return Status::InvalidArgument(
+            dbname_, "does not exist (create_if_missing is false)");
       }
     } else {
-      return Status::InvalidArgument(
-          dbname_, "does not exist (create_if_missing is false)");
-    }
-  } else {
-    if (options_.error_if_exists) {
-      return Status::InvalidArgument(
-          dbname_, "exists (error_if_exists is true)");
+      if (options_.error_if_exists) {
+        return Status::InvalidArgument(
+            dbname_, "exists (error_if_exists is true)");
+      }
     }
   }
 
-  s = versions_->Recover();
+  Status s = versions_->Recover();
   if (s.ok()) {
     SequenceNumber max_sequence(0);
 
@@ -897,9 +899,12 @@ Status DBImpl::GetUpdatesSince(SequenceNumber seq,
     return s;
   }
   //  list wal files in archive dir.
-  s = ListAllWALFiles(ArchivalDirectory(dbname_), &walFiles, kArchivedLogFile);
-  if (!s.ok()) {
-    return s;
+  std::string archivedir = ArchivalDirectory(dbname_);
+  if (env_->FileExists(archivedir)) {
+    s = ListAllWALFiles(archivedir, &walFiles, kArchivedLogFile);
+    if (!s.ok()) {
+      return s;
+    }
   }
 
   if (walFiles.empty()) {
diff --git a/db/transaction_log_iterator_impl.cc b/db/transaction_log_iterator_impl.cc
index c2ca14a36..bc118b8c2 100644
--- a/db/transaction_log_iterator_impl.cc
+++ b/db/transaction_log_iterator_impl.cc
@@ -16,8 +16,8 @@ TransactionLogIteratorImpl::TransactionLogIteratorImpl(
   isValid_(true),
   currentFileIndex_(0),
   currentLogReader_(NULL) {
-    assert( files_ != NULL);
-  }
+  assert( files_ != NULL);
+}
 
 LogReporter
 TransactionLogIteratorImpl::NewLogReporter(const uint64_t logNumber) {
diff --git a/include/leveldb/write_batch.h b/include/leveldb/write_batch.h
index ac0e2e11d..6546cadaa 100644
--- a/include/leveldb/write_batch.h
+++ b/include/leveldb/write_batch.h
@@ -51,9 +51,12 @@ class WriteBatch {
   };
   Status Iterate(Handler* handler) const;
 
-  // Returns the serialized string
+  // Retrive the serialized version of this batch.
   std::string Data() { return rep_; }
 
+  // Constructor with a serialized string object
+  WriteBatch(std::string rep): rep_(rep) {}
+
  private:
   friend class WriteBatchInternal;