keep snapshot on log delete fail (#391)

- Improvement: Cleaned up snapshot writing for CompactCAS/FileCas/Cache/Project stores
- Improvement: Safer recovery when failing to delete log for CompactCAS/FileCas/Cache/Project stores
- Improvement: Added log file reset when writing snapshot at startup for FileCas

1 files changed, 7 insertions, 54 deletions

diff --git a/src/zenserver/projectstore/projectstore.cpp b/src/zenserver/projectstore/projectstore.cpp
index 071aab137..6a55efdb7 100644
--- a/src/zenserver/projectstore/projectstore.cpp
+++ b/src/zenserver/projectstore/projectstore.cpp
@@ -1643,31 +1643,9 @@ ProjectStore::Oplog::WriteIndexSnapshot()
 
 	namespace fs = std::filesystem;
 
-	fs::path IndexPath	   = m_BasePath / "ops.zidx";
-	fs::path TempIndexPath = m_BasePath / "ops.zidx.tmp";
-
-	// Move index away, we keep it if something goes wrong
-	if (IsFile(TempIndexPath))
-	{
-		std::error_code Ec;
-		if (!RemoveFile(TempIndexPath, Ec) || Ec)
-		{
-			ZEN_WARN("oplog '{}/{}': snapshot failed to clean up temp snapshot at {}, reason: '{}'",
-					 GetOuterProject()->Identifier,
-					 m_OplogId,
-					 TempIndexPath,
-					 Ec.message());
-			return;
-		}
-	}
-
+	const fs::path IndexPath = m_BasePath / "ops.zidx";
 	try
 	{
-		if (IsFile(IndexPath))
-		{
-			RenameFile(IndexPath, TempIndexPath);
-		}
-
 		// Write the current state of the location map to a new index state
 		std::vector<uint32_t>		   LSNEntries;
 		std::vector<Oid>			   Keys;
@@ -1781,7 +1759,11 @@ ProjectStore::Oplog::WriteIndexSnapshot()
 		ObjectIndexFile.MoveTemporaryIntoPlace(IndexPath, Ec);
 		if (Ec)
 		{
-			throw std::system_error(Ec, fmt::format("Failed to move temp file '{}' to '{}'", ObjectIndexFile.GetPath(), IndexPath));
+			throw std::system_error(Ec,
+									fmt::format("Snapshot failed to rename new snapshot '{}' to '{}', reason: '{}'",
+												ObjectIndexFile.GetPath(),
+												IndexPath,
+												Ec.message()));
 		}
 		EntryCount		   = LSNEntries.size();
 		m_LogFlushPosition = IndexLogPosition;
@@ -1789,35 +1771,6 @@ ProjectStore::Oplog::WriteIndexSnapshot()
 	catch (const std::exception& Err)
 	{
 		ZEN_WARN("oplog '{}/{}': snapshot FAILED, reason: '{}'", m_OuterProject->Identifier, m_OplogId, Err.what());
-
-		// Restore any previous snapshot
-
-		if (IsFile(TempIndexPath))
-		{
-			std::error_code Ec;
-			RemoveFile(IndexPath, Ec);	// We don't care if this fails, we try to move the old temp file regardless
-			RenameFile(TempIndexPath, IndexPath, Ec);
-			if (Ec)
-			{
-				ZEN_WARN("oplog '{}/{}': snapshot failed to restore old snapshot from {}, reason: '{}'",
-						 m_OuterProject->Identifier,
-						 m_OplogId,
-						 TempIndexPath,
-						 Ec.message());
-			}
-		}
-	}
-	if (IsFile(TempIndexPath))
-	{
-		std::error_code Ec;
-		if (!RemoveFile(TempIndexPath, Ec) || Ec)
-		{
-			ZEN_WARN("oplog '{}/{}': snapshot failed to remove temporary file {}, reason: '{}'",
-					 m_OuterProject->Identifier,
-					 m_OplogId,
-					 TempIndexPath,
-					 Ec.message());
-		}
 	}
 }
 
@@ -1827,7 +1780,7 @@ ProjectStore::Oplog::ReadIndexSnapshot()
 	ZEN_MEMSCOPE(GetProjectstoreTag());
 	ZEN_TRACE_CPU("Oplog::ReadIndexSnapshot");
 
-	std::filesystem::path IndexPath = m_BasePath / "ops.zidx";
+	const std::filesystem::path IndexPath = m_BasePath / "ops.zidx";
 	if (IsFile(IndexPath))
 	{
 		uint64_t   EntryCount = 0;