From 9055f63742231dc87284e36e0de60867b9d982f7 Mon Sep 17 00:00:00 2001
From: Benguang Zhao <bgzhao@taosdata.com>
Date: Fri, 30 Sep 2022 18:54:49 +0800
Subject: [PATCH] fix: ftruncate WAL log after the last valid WAL record
 properly in walScanLogGetLastVer

---
 source/libs/wal/src/walMeta.c | 79 +++++++++++++++++++----------------
 1 file changed, 42 insertions(+), 37 deletions(-)

diff --git a/source/libs/wal/src/walMeta.c b/source/libs/wal/src/walMeta.c
index 597fd0000b..797393c47e 100644
--- a/source/libs/wal/src/walMeta.c
+++ b/source/libs/wal/src/walMeta.c
@@ -45,12 +45,11 @@ static FORCE_INLINE int walBuildTmpMetaName(SWal* pWal, char* buf) {
 
 static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal) {
   int32_t sz = taosArrayGetSize(pWal->fileInfoSet);
-  ASSERT(sz > 0);
-#if 0
-  for (int i = 0; i < sz; i++) {
-    SWalFileInfo* pFileInfo = taosArrayGet(pWal->fileInfoSet, i);
+  if (sz <= 0) {
+    wError("No WAL log file found.");
+    terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
+    return -1;
   }
-#endif
 
   SWalFileInfo* pLastFileInfo = taosArrayGet(pWal->fileInfoSet, sz - 1);
   char          fnameStr[WAL_FILE_LEN];
@@ -61,7 +60,7 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal) {
   int32_t readSize = TMIN(WAL_SCAN_BUF_SIZE, fileSize);
   pLastFileInfo->fileSize = fileSize;
 
-  TdFilePtr pFile = taosOpenFile(fnameStr, TD_FILE_READ);
+  TdFilePtr pFile = taosOpenFile(fnameStr, TD_FILE_READ | TD_FILE_WRITE);
   if (pFile == NULL) {
     terrno = TAOS_SYSTEM_ERROR(errno);
     return -1;
@@ -69,28 +68,30 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal) {
 
   uint64_t magic = WAL_MAGIC;
 
-  char* buf = taosMemoryMalloc(readSize + 5);
+  char* buf = taosMemoryMalloc(readSize + sizeof(uint64_t));
   if (buf == NULL) {
-    taosCloseFile(&pFile);
     terrno = TSDB_CODE_WAL_OUT_OF_MEMORY;
-    return -1;
+    goto _err;
   }
 
   int64_t offset;
   offset = taosLSeekFile(pFile, -readSize, SEEK_END);
   if (readSize != taosReadFile(pFile, buf, readSize)) {
-    taosMemoryFree(buf);
-    taosCloseFile(&pFile);
     terrno = TAOS_SYSTEM_ERROR(errno);
-    return -1;
+    goto _err;
   }
 
+  int64_t walCkHeadSz = sizeof(SWalCkHead);
   char* found = NULL;
   while (1) {
     char* haystack = buf;
-    char* candidate;
+    char* candidate = NULL;
     while ((candidate = tmemmem(haystack, readSize - (haystack - buf), (char*)&magic, sizeof(uint64_t))) != NULL) {
       // read and validate
+      int64_t len = readSize - (candidate - buf);
+      if (len < walCkHeadSz) {
+          break;
+      }
       SWalCkHead* logContent = (SWalCkHead*)candidate;
       if (walValidHeadCksum(logContent) == 0 && walValidBodyCksum(logContent) == 0) {
         found = candidate;
@@ -98,35 +99,26 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal) {
       haystack = candidate + 1;
     }
     if (found || offset == 0) break;
-    offset = TMIN(0, offset - readSize + sizeof(uint64_t));
-    int64_t offset2 = taosLSeekFile(pFile, offset, SEEK_SET);
-    ASSERT(offset == offset2);
-    if (readSize != taosReadFile(pFile, buf, readSize)) {
-      taosMemoryFree(buf);
-      taosCloseFile(&pFile);
+
+    // go backwards, i.e. by at most one WAL scan buf size
+    offset = TMAX(0, offset - readSize + walCkHeadSz);
+    int64_t ret = taosLSeekFile(pFile, offset, SEEK_SET);
+    if (ret < 0)  {
+      wError("failed to lseek file due to %s. offset:%lld", strerror(errno), offset);
       terrno = TAOS_SYSTEM_ERROR(errno);
-      return -1;
+      goto _err;
     }
-#if 0
-    if (found == buf) {
-      SWalCkHead* logContent = (SWalCkHead*)found;
-      if (walValidHeadCksum(logContent) != 0 || walValidBodyCksum(logContent) != 0) {
-        // file has to be deleted
-        taosMemoryFree(buf);
-        taosCloseFile(&pFile);
-        terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
-        return -1;
-      }
+    ASSERT(offset == ret);
+    if (readSize != taosReadFile(pFile, buf, readSize)) {
+      terrno = TAOS_SYSTEM_ERROR(errno);
+      goto _err;
     }
-#endif
   }
 
   if (found == NULL) {
-    // file corrupted, no complete log
-    // TODO delete and search in previous files
-    /*ASSERT(0);*/
+    wError("WAL log file corrupted: no valid WAL record found. file: %s", fnameStr);
     terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
-    return -1;
+    goto _err;
   }
 
   // truncate file
@@ -137,15 +129,28 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal) {
   if (lastEntryEndOffset != fileSize) {
     wWarn("vgId:%d repair meta truncate file %s to %ld, orig size %ld", pWal->cfg.vgId, fnameStr, lastEntryEndOffset,
           fileSize);
-    taosFtruncateFile(pFile, lastEntryEndOffset);
+    if (taosFtruncateFile(pFile, lastEntryEndOffset) < 0) {
+        wError("failed to truncate file due to %s. file:%s", strerror(errno), fnameStr);
+        terrno = TAOS_SYSTEM_ERROR(errno);
+        goto _err;
+    }
+    if (taosFsyncFile(pFile) < 0) {
+        wError("failed to fsync file due to %s. file:%s", strerror(errno), fnameStr);
+        terrno = TAOS_SYSTEM_ERROR(errno);
+        goto _err;
+    }
     ((SWalFileInfo*)taosArrayGetLast(pWal->fileInfoSet))->fileSize = lastEntryEndOffset;
     pWal->totSize -= (fileSize - lastEntryEndOffset);
   }
 
   taosCloseFile(&pFile);
   taosMemoryFree(buf);
-
   return retVer;
+
+_err:
+  taosCloseFile(&pFile);
+  taosMemoryFree(buf);
+  return -1;
 }
 
 int walCheckAndRepairMeta(SWal* pWal) {
-- 
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