From 0f40fe4bc71d53346027fa8d1a12815c25dbd19a Mon Sep 17 00:00:00 2001
From: sdong <siying.d@fb.com>
Date: Tue, 15 Apr 2014 09:06:13 -0700
Subject: [PATCH] When creating a new DB, fail it when wal_dir contains
 existing log files

Summary: Current behavior of creating new DB is, if there is existing log files, we will go ahead and replay them on top of empty DB. This is a behavior that no user would expect. With this patch, we will fail the creation if a user creates a DB with existing log files.

Test Plan: make all check

Reviewers: haobo, igor, ljin

Reviewed By: haobo

CC: nkg-, yhchiang, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D17817
---
 db/db_impl.cc | 15 +++++++++++----
 db/db_test.cc | 25 +++++++++++++++++++------
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/db/db_impl.cc b/db/db_impl.cc
index 918402df51..77d6ca04c3 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -1062,6 +1062,7 @@ Status DBImpl::Recover(
     bool error_if_log_file_exist) {
   mutex_.AssertHeld();
 
+  bool is_new_db = false;
   assert(db_lock_ == nullptr);
   if (!read_only) {
     // We call CreateDirIfMissing() as the directory may already exist (if we
@@ -1090,6 +1091,7 @@ Status DBImpl::Recover(
       if (options_.create_if_missing) {
         // TODO: add merge_operator name check
         s = NewDB();
+        is_new_db = true;
         if (!s.ok()) {
           return s;
         }
@@ -1140,10 +1142,15 @@ Status DBImpl::Recover(
     for (size_t i = 0; i < filenames.size(); i++) {
       uint64_t number;
       FileType type;
-      if (ParseFileName(filenames[i], &number, &type)
-          && type == kLogFile
-          && ((number >= min_log) || (number == prev_log))) {
-        logs.push_back(number);
+      if (ParseFileName(filenames[i], &number, &type) && type == kLogFile) {
+        if (is_new_db) {
+          return Status::Corruption(
+              "While creating a new Db, wal_dir contains "
+              "existing log file: ",
+              filenames[i]);
+        } else if ((number >= min_log) || (number == prev_log)) {
+          logs.push_back(number);
+        }
       }
     }
 
diff --git a/db/db_test.cc b/db/db_test.cc
index d3c5e2d555..c9578a65ac 100644
--- a/db/db_test.cc
+++ b/db/db_test.cc
@@ -2095,7 +2095,24 @@ TEST(DBTest, IgnoreRecoveredLog) {
     ASSERT_EQ(one, Get("bar"));
     Close();
     Destroy(&options);
+    Reopen(&options);
+    Close();
 
+    // copy the logs from backup back to wal dir
+    env_->CreateDirIfMissing(options.wal_dir);
+    for (auto& log : logs) {
+      if (log != ".." && log != ".") {
+        CopyFile(backup_logs + "/" + log, options.wal_dir + "/" + log);
+      }
+    }
+    // assert that we successfully recovered only from logs, even though we
+    // destroyed the DB
+    Reopen(&options);
+    ASSERT_EQ(two, Get("foo"));
+    ASSERT_EQ(one, Get("bar"));
+
+    // Recovery will fail if DB directory doesn't exist.
+    Destroy(&options);
     // copy the logs from backup back to wal dir
     env_->CreateDirIfMissing(options.wal_dir);
     for (auto& log : logs) {
@@ -2105,12 +2122,8 @@ TEST(DBTest, IgnoreRecoveredLog) {
         env_->DeleteFile(backup_logs + "/" + log);
       }
     }
-    // assert that we successfully recovered only from logs, even though we
-    // destroyed the DB
-    Reopen(&options);
-    ASSERT_EQ(two, Get("foo"));
-    ASSERT_EQ(one, Get("bar"));
-    Close();
+    Status s = TryReopen(&options);
+    ASSERT_TRUE(!s.ok());
   } while (ChangeOptions());
 }