Add ReadOnly Support for IDevice (#870)

* add readOnly flag in streamProvider for LocalStorageDevice

* add linux readOnly flag for managed device

* add explicit readOnly assignment for parameter

libs/common/StreamProvider.cs

@@ -120,8 +120,9 @@ public class StreamProviderFactory
         /// <param name="locationType">Type of location of files the stream provider reads from / writes to</param>
         /// <param name="connectionString">Connection string to Azure Storage, if applicable</param>
         /// <param name="resourceAssembly">Assembly from which to load the embedded resource, if applicable.</param>
+        /// <param name="readOnly">Open file in read only mode</param>
         /// <returns>StreamProvider instance</returns>
-        public static IStreamProvider GetStreamProvider(FileLocationType locationType, string connectionString = null, Assembly resourceAssembly = null)
+        public static IStreamProvider GetStreamProvider(FileLocationType locationType, string connectionString = null, Assembly resourceAssembly = null, bool readOnly = false)
         {
             switch (locationType)
             {
@@ -130,7 +131,7 @@ public static IStreamProvider GetStreamProvider(FileLocationType locationType, s
                         throw new ArgumentException("Azure Storage connection string is required to read/write to Azure Storage", nameof(connectionString));
                     return new AzureStreamProvider(connectionString);
                 case FileLocationType.Local:
-                    return new LocalFileStreamProvider();
+                    return new LocalFileStreamProvider(readOnly);
                 case FileLocationType.EmbeddedResource:
                     if (resourceAssembly == null)
                         throw new ArgumentException(
@@ -181,11 +182,18 @@ protected override long GetBytesToWrite(byte[] bytes, IDevice device)
     /// </summary>
     internal class LocalFileStreamProvider : StreamProviderBase
     {
+        private readonly bool readOnly;
+
+        public LocalFileStreamProvider(bool readOnly = false)
+        {
+            this.readOnly = readOnly;
+        }
+
         protected override IDevice GetDevice(string path)
         {
             var fileInfo = new FileInfo(path);
 
-            INamedDeviceFactory settingsDeviceFactoryCreator = new LocalStorageNamedDeviceFactory(disableFileBuffering: false);
+            INamedDeviceFactory settingsDeviceFactoryCreator = new LocalStorageNamedDeviceFactory(disableFileBuffering: false, readOnly: readOnly);
             settingsDeviceFactoryCreator.Initialize("");
             var settingsDevice = settingsDeviceFactoryCreator.Get(new FileDescriptor(fileInfo.DirectoryName, fileInfo.Name));
             settingsDevice.Initialize(-1, epoch: null, omitSegmentIdFromFilename: true);

libs/host/ServerSettingsManager.cs

@@ -259,7 +259,7 @@ private static bool TryImportServerOptions(string path, ConfigFileType configFil
         {
             var assembly = fileLocationType == FileLocationType.EmbeddedResource ? Assembly.GetExecutingAssembly() : null;
 
-            var streamProvider = StreamProviderFactory.GetStreamProvider(fileLocationType, connString, assembly);
+            var streamProvider = StreamProviderFactory.GetStreamProvider(fileLocationType, connString, assembly, readOnly: true);
             var configProvider = ConfigProviderFactory.GetConfigProvider(configFileType);
 
             using var stream = streamProvider.Read(path);

libs/storage/Tsavorite/cs/src/core/Device/Devices.cs

@@ -20,26 +20,27 @@ public static class Devices
         /// Create a storage device for the log
         /// </summary>
         /// <param name="logPath">Path to file that will store the log (empty for null device)</param>
-        /// <param name="preallocateFile">Whether we try to preallocate the file on creation</param>
+        /// <param name="preallocateFile">Whether we try to pre-allocate the file on creation</param>
         /// <param name="deleteOnClose">Delete files on close</param>
-        /// <param name="capacity">The maximal number of bytes this storage device can accommondate, or CAPACITY_UNSPECIFIED if there is no such limit</param>
+        /// <param name="capacity">The maximal number of bytes this storage device can accommodate, or CAPACITY_UNSPECIFIED if there is no such limit</param>
         /// <param name="recoverDevice">Whether to recover device metadata from existing files</param>
         /// <param name="useIoCompletionPort">Whether we use IO completion port with polling</param>
         /// <param name="disableFileBuffering">Whether file buffering (during write) is disabled (default of true requires aligned writes)</param>
         /// <param name="useNativeDeviceLinux">Use native device on Linux, instead of managed device based on FileStream</param>
+        /// <param name="readOnly">Open file in readOnly mode</param>
         /// <param name="logger"></param>
         /// <returns>Device instance</returns>
-        public static IDevice CreateLogDevice(string logPath, bool preallocateFile = false, bool deleteOnClose = false, long capacity = CAPACITY_UNSPECIFIED, bool recoverDevice = false, bool useIoCompletionPort = false, bool disableFileBuffering = true, bool useNativeDeviceLinux = false, ILogger logger = null)
+        public static IDevice CreateLogDevice(string logPath, bool preallocateFile = false, bool deleteOnClose = false, long capacity = CAPACITY_UNSPECIFIED, bool recoverDevice = false, bool useIoCompletionPort = false, bool disableFileBuffering = true, bool useNativeDeviceLinux = false, bool readOnly = false, ILogger logger = null)
         {
             if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
                 if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) && useNativeDeviceLinux)
                     return new NativeStorageDevice(logPath, deleteOnClose, disableFileBuffering, capacity, logger: logger);
                 else
-                    return new ManagedLocalStorageDevice(logPath, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice);
+                    return new ManagedLocalStorageDevice(logPath, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice, readOnly: readOnly);
             }
             else
-                return new LocalStorageDevice(logPath, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice, useIoCompletionPort);
+                return new LocalStorageDevice(logPath, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice, useIoCompletionPort, readOnly: readOnly);
         }
     }
 }

libs/storage/Tsavorite/cs/src/core/Device/LocalStorageDevice.cs

@@ -39,6 +39,7 @@ public unsafe class LocalStorageDevice : StorageDeviceBase
         private readonly ConcurrentQueue<SimpleAsyncResult> results;
         private static uint sectorSize = 0;
         private bool _disposed;
+        readonly bool readOnly;
 
         /// <summary>
         /// Number of pending reads on device
@@ -62,8 +63,10 @@ public LocalStorageDevice(string filename,
                                   bool deleteOnClose = false,
                                   bool disableFileBuffering = true,
                                   long capacity = Devices.CAPACITY_UNSPECIFIED,
-                                  bool recoverDevice = false, bool useIoCompletionPort = false)
-            : this(filename, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice, null, useIoCompletionPort)
+                                  bool recoverDevice = false,
+                                  bool useIoCompletionPort = false,
+                                  bool readOnly = false)
+            : this(filename, preallocateFile, deleteOnClose, disableFileBuffering, capacity, recoverDevice, null, useIoCompletionPort, readOnly: readOnly)
         {
         }
 
@@ -96,7 +99,8 @@ protected internal LocalStorageDevice(string filename,
                                       long capacity = Devices.CAPACITY_UNSPECIFIED,
                                       bool recoverDevice = false,
                                       IEnumerable<KeyValuePair<int, SafeFileHandle>> initialLogFileHandles = null,
-                                      bool useIoCompletionPort = true)
+                                      bool useIoCompletionPort = true,
+                                      bool readOnly = false)
                 : base(filename, GetSectorSize(filename), capacity)
         {
             if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -134,6 +138,7 @@ protected internal LocalStorageDevice(string filename,
             this.preallocateFile = preallocateFile;
             this.deleteOnClose = deleteOnClose;
             this.disableFileBuffering = disableFileBuffering;
+            this.readOnly = readOnly;
             results = new ConcurrentQueue<SimpleAsyncResult>();
 
             logHandles = initialLogFileHandles != null
@@ -388,14 +393,14 @@ public override long GetFileSize(int segment)
         }
 
         private SafeFileHandle CreateHandle(int segmentId, bool disableFileBuffering, bool deleteOnClose, bool preallocateFile, long segmentSize, string fileName, IntPtr ioCompletionPort)
-            => CreateHandle(segmentId, disableFileBuffering, deleteOnClose, preallocateFile, segmentSize, fileName, ioCompletionPort, OmitSegmentIdFromFileName);
+            => CreateHandle(segmentId, disableFileBuffering, deleteOnClose, preallocateFile, segmentSize, fileName, ioCompletionPort, OmitSegmentIdFromFileName, readOnly);
 
         /// <summary>
         /// Creates a SafeFileHandle for the specified segment. This can be used by derived classes to prepopulate logHandles in the constructor.
         /// </summary>
-        protected internal static SafeFileHandle CreateHandle(int segmentId, bool disableFileBuffering, bool deleteOnClose, bool preallocateFile, long segmentSize, string fileName, IntPtr ioCompletionPort, bool omitSegmentId = false)
+        protected internal static SafeFileHandle CreateHandle(int segmentId, bool disableFileBuffering, bool deleteOnClose, bool preallocateFile, long segmentSize, string fileName, IntPtr ioCompletionPort, bool omitSegmentId = false, bool readOnly = false)
         {
-            uint fileAccess = Native32.GENERIC_READ | Native32.GENERIC_WRITE;
+            uint fileAccess = readOnly ? Native32.GENERIC_READ : Native32.GENERIC_READ | Native32.GENERIC_WRITE;
             uint fileShare = unchecked(((uint)FileShare.ReadWrite & ~(uint)FileShare.Inheritable));
             uint fileCreation = unchecked((uint)FileMode.OpenOrCreate);
             uint fileFlags = Native32.FILE_FLAG_OVERLAPPED;

libs/storage/Tsavorite/cs/src/core/Device/ManagedLocalStorageDevice.cs

@@ -20,6 +20,7 @@ public sealed class ManagedLocalStorageDevice : StorageDeviceBase
         private readonly bool deleteOnClose;
         private readonly bool disableFileBuffering;
         private readonly bool osReadBuffering;
+        private readonly bool readOnly;
         private readonly SafeConcurrentDictionary<int, (AsyncPool<Stream>, AsyncPool<Stream>)> logHandles;
         private readonly SectorAlignedBufferPool pool;
 
@@ -40,7 +41,8 @@ public sealed class ManagedLocalStorageDevice : StorageDeviceBase
         /// <param name="capacity">The maximal number of bytes this storage device can accommondate, or CAPACITY_UNSPECIFIED if there is no such limit</param>
         /// <param name="recoverDevice">Whether to recover device metadata from existing files</param>
         /// <param name="osReadBuffering">Enable OS read buffering</param>
-        public ManagedLocalStorageDevice(string filename, bool preallocateFile = false, bool deleteOnClose = false, bool disableFileBuffering = true, long capacity = Devices.CAPACITY_UNSPECIFIED, bool recoverDevice = false, bool osReadBuffering = false)
+        /// <param name="readOnly">Open file in readOnly mode</param>
+        public ManagedLocalStorageDevice(string filename, bool preallocateFile = false, bool deleteOnClose = false, bool disableFileBuffering = true, long capacity = Devices.CAPACITY_UNSPECIFIED, bool recoverDevice = false, bool osReadBuffering = false, bool readOnly = false)
             : base(filename, GetSectorSize(filename), capacity)
         {
             pool = new(1, 1);
@@ -55,6 +57,7 @@ public ManagedLocalStorageDevice(string filename, bool preallocateFile = false,
             this.deleteOnClose = deleteOnClose;
             this.disableFileBuffering = disableFileBuffering;
             this.osReadBuffering = osReadBuffering;
+            this.readOnly = readOnly;
             logHandles = new();
             if (recoverDevice)
                 RecoverFiles();
@@ -420,7 +423,7 @@ private Stream CreateReadHandle(int segmentId)
 
             var logReadHandle = new FileStream(
                 GetSegmentName(segmentId), FileMode.OpenOrCreate,
-                FileAccess.Read, FileShare.ReadWrite, 512, fo);
+                FileAccess.Read, readOnly ? FileShare.Read : FileShare.ReadWrite, 512, fo);
 
             return logReadHandle;
         }

libs/storage/Tsavorite/cs/src/core/Device/StorageDeviceBase.cs

@@ -82,8 +82,9 @@ public abstract class StorageDeviceBase : IDevice
         /// </summary>
         /// <param name="filename">Name of the file to use</param>
         /// <param name="sectorSize">The smallest unit of write of the underlying storage device (e.g. 512 bytes for a disk) </param>
-        /// <param name="capacity">The maximal number of bytes this storage device can accommondate, or CAPAPCITY_UNSPECIFIED if there is no such limit </param>
-        public StorageDeviceBase(string filename, uint sectorSize, long capacity)
+        /// <param name="capacity">The maximal number of bytes this storage device can accommodate, or CAPAPCITY_UNSPECIFIED if there is no such limit </param>
+        /// <param name="readOnly">Open file in readOnly mode </param>
+        public StorageDeviceBase(string filename, uint sectorSize, long capacity, bool readOnly = false)
         {
             FileName = filename;
             SectorSize = sectorSize;

libs/storage/Tsavorite/cs/src/core/Index/CheckpointManagement/LocalStorageNamedDeviceFactory.cs

@@ -21,6 +21,7 @@ public class LocalStorageNamedDeviceFactory : INamedDeviceFactory
         readonly bool preallocateFile;
         readonly bool disableFileBuffering;
         readonly bool useNativeDeviceLinux;
+        readonly bool readOnly;
         readonly ILogger logger;
 
         /// <summary>
@@ -32,13 +33,14 @@ public class LocalStorageNamedDeviceFactory : INamedDeviceFactory
         /// <param name="throttleLimit">Throttle limit (max number of pending I/Os) for this device instance</param>
         /// <param name="useNativeDeviceLinux">Use native device on Linux</param>
         /// <param name="logger"></param>
-        public LocalStorageNamedDeviceFactory(bool preallocateFile = false, bool deleteOnClose = false, bool disableFileBuffering = true, int? throttleLimit = null, bool useNativeDeviceLinux = false, ILogger logger = null)
+        public LocalStorageNamedDeviceFactory(bool preallocateFile = false, bool deleteOnClose = false, bool disableFileBuffering = true, int? throttleLimit = null, bool useNativeDeviceLinux = false, bool readOnly = false, ILogger logger = null)
         {
             this.preallocateFile = preallocateFile;
             this.deleteOnClose = deleteOnClose;
             this.disableFileBuffering = disableFileBuffering;
             this.throttleLimit = throttleLimit;
             this.useNativeDeviceLinux = useNativeDeviceLinux;
+            this.readOnly = readOnly;
             this.logger = logger;
         }
 
@@ -51,15 +53,21 @@ public void Initialize(string baseName)
         /// <inheritdoc />
         public IDevice Get(FileDescriptor fileInfo)
         {
-            var device = Devices.CreateLogDevice(Path.Combine(baseName, fileInfo.directoryName, fileInfo.fileName), preallocateFile: preallocateFile, deleteOnClose: deleteOnClose, disableFileBuffering: disableFileBuffering, useNativeDeviceLinux: useNativeDeviceLinux, logger: logger);
+            var device = Devices.CreateLogDevice(
+                Path.Combine(baseName, fileInfo.directoryName, fileInfo.fileName),
+                preallocateFile: preallocateFile,
+                deleteOnClose: deleteOnClose,
+                disableFileBuffering: disableFileBuffering,
+                useNativeDeviceLinux: useNativeDeviceLinux,
+                readOnly: readOnly,
+                logger: logger);
             if (throttleLimit.HasValue)
             {
                 device.ThrottleLimit = throttleLimit.Value;
             }
             return device;
         }
 
-
         /// <inheritdoc />
         public IEnumerable<FileDescriptor> ListContents(string path)
         {