From b434ac2fc9663fc41c7bd42cfdaf74dbd085e17e Mon Sep 17 00:00:00 2001
From: Benguang Zhao <bgzhao@taosdata.com>
Date: Wed, 28 Jun 2023 14:43:47 +0800
Subject: [PATCH] enh: improve walScanLogGetLastVer

---
 source/libs/wal/src/walMeta.c | 60 +++++++++++++++++------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/source/libs/wal/src/walMeta.c b/source/libs/wal/src/walMeta.c
index a12f8051ba..6fa3c8ebfe 100644
--- a/source/libs/wal/src/walMeta.c
+++ b/source/libs/wal/src/walMeta.c
@@ -47,9 +47,7 @@ static FORCE_INLINE int walBuildTmpMetaName(SWal* pWal, char* buf) {
 }
 
 static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
-  int32_t sz = taosArrayGetSize(pWal->fileInfoSet);
-  terrno = TSDB_CODE_SUCCESS;
-
+  int32_t       sz = taosArrayGetSize(pWal->fileInfoSet);
   SWalFileInfo* pFileInfo = taosArrayGet(pWal->fileInfoSet, fileIdx);
   char          fnameStr[WAL_FILE_LEN];
   walBuildLogName(pWal, pFileInfo->firstVer, fnameStr);
@@ -74,13 +72,12 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
   int64_t  capacity = 0;
   int64_t  readSize = 0;
   char*    buf = NULL;
-  bool     firstTrial = pFileInfo->fileSize < fileSize;
   int64_t  offset = TMIN(pFileInfo->fileSize, fileSize);
-  int64_t  offsetForward = offset - stepSize + walCkHeadSz - 1;
-  int64_t  offsetBackward = offset;
   int64_t  retVer = -1;
   int64_t  lastEntryBeginOffset = 0;
   int64_t  lastEntryEndOffset = 0;
+  int64_t  recordLen = 0;
+  bool     forwardStage = false;
 
   // check recover size
   if (2 * tsWalFsyncDataSizeLimit + offset < end) {
@@ -91,14 +88,8 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
 
   // search for the valid last WAL entry, e.g. block by block
   while (1) {
-    offset = (firstTrial) ? TMIN(fileSize, offsetForward + stepSize - walCkHeadSz + 1)
-                          : TMAX(0, offsetBackward - stepSize + walCkHeadSz - 1);
+    offset = (lastEntryEndOffset > 0) ? offset : TMAX(0, offset - stepSize + walCkHeadSz - 1);
     end = TMIN(offset + stepSize, fileSize);
-    if (firstTrial) {
-      offsetForward = offset;
-    } else {
-      offsetBackward = offset;
-    }
 
     readSize = end - offset;
     capacity = readSize + sizeof(magic);
@@ -129,7 +120,16 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
     int64_t     pos = 0;
     SWalCkHead* logContent = NULL;
 
-    while ((candidate = tmemmem(haystack, readSize - (haystack - buf), (char*)&magic, sizeof(magic))) != NULL) {
+    while (true) {
+      forwardStage = (lastEntryEndOffset > 0 || offset == 0);
+      terrno = TSDB_CODE_SUCCESS;
+      if (forwardStage) {
+        candidate = (readSize - (haystack - buf)) > 0 ? haystack : NULL;
+      } else {
+        candidate = tmemmem(haystack, readSize - (haystack - buf), (char*)&magic, sizeof(magic));
+      }
+
+      if (candidate == NULL) break;
       pos = candidate - buf;
 
       // validate head
@@ -137,13 +137,20 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
       if (len < walCkHeadSz) {
         break;
       }
+
       logContent = (SWalCkHead*)(buf + pos);
+      if (logContent->magic != WAL_MAGIC) {
+        terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
+        ASSERT(forwardStage);
+        wError("vgId:%d, wal magic is corrupted. offset:%" PRId64 ", file:%s ", pWal->cfg.vgId, offset + pos, fnameStr);
+        break;
+      }
       if (walValidHeadCksum(logContent) != 0) {
         terrno = TSDB_CODE_WAL_CHKSUM_MISMATCH;
         wWarn("vgId:%d, failed to validate checksum of wal entry header. offset:%" PRId64 ", file:%s", pWal->cfg.vgId,
               offset + pos, fnameStr);
         haystack = buf + pos + 1;
-        if (firstTrial) {
+        if (forwardStage) {
           break;
         } else {
           continue;
@@ -151,9 +158,9 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
       }
 
       // validate body
-      int64_t size = walCkHeadSz + logContent->head.bodyLen;
-      if (len < size) {
-        int64_t extraSize = size - len;
+      recordLen = walCkHeadSz + logContent->head.bodyLen;
+      if (len < recordLen) {
+        int64_t extraSize = recordLen - len;
         if (capacity < readSize + extraSize + sizeof(magic)) {
           capacity += extraSize;
           void* ptr = taosMemoryRealloc(buf, capacity);
@@ -184,7 +191,7 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
         wWarn("vgId:%d, failed to validate checksum of wal entry body. offset:%" PRId64 ", file:%s", pWal->cfg.vgId,
               offset + pos, fnameStr);
         haystack = buf + pos + 1;
-        if (firstTrial) {
+        if (forwardStage) {
           break;
         } else {
           continue;
@@ -194,21 +201,14 @@ static FORCE_INLINE int64_t walScanLogGetLastVer(SWal* pWal, int32_t fileIdx) {
       // found one
       retVer = logContent->head.version;
       lastEntryBeginOffset = offset + pos;
-      lastEntryEndOffset = offset + pos + sizeof(SWalCkHead) + logContent->head.bodyLen;
+      lastEntryEndOffset = offset + pos + recordLen;
 
       // try next
-      haystack = buf + pos + 1;
+      haystack = buf + pos + recordLen;
     }
 
-    if (end == fileSize) firstTrial = false;
-    if (firstTrial) {
-      if (terrno == TSDB_CODE_SUCCESS) {
-        continue;
-      } else {
-        firstTrial = false;
-      }
-    }
-    if (retVer >= 0 || offset == 0) break;
+    offset = (lastEntryEndOffset > 0) ? lastEntryEndOffset : offset;
+    if (forwardStage && (terrno != TSDB_CODE_SUCCESS || end == fileSize)) break;
   }
 
   if (retVer < 0) {