Merge pull request #47 from crupest/avatar-enhance

Use etag for avatar cache.

1 files changed, 82 insertions, 15 deletions

diff --git a/Timeline/Services/UserAvatarService.cs b/Timeline/Services/UserAvatarService.cs
index a83b8a52..7b1f405c 100644
--- a/Timeline/Services/UserAvatarService.cs
+++ b/Timeline/Services/UserAvatarService.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Hosting;

 using Microsoft.EntityFrameworkCore;

 using Microsoft.Extensions.DependencyInjection;

+using Microsoft.Extensions.DependencyInjection.Extensions;

 using Microsoft.Extensions.Logging;

 using SixLabors.ImageSharp;

 using SixLabors.ImageSharp.Formats;

@@ -65,6 +66,12 @@ namespace Timeline.Services
     public interface IDefaultUserAvatarProvider

     {

         /// <summary>

+        /// Get the etag of default avatar.

+        /// </summary>

+        /// <returns></returns>

+        Task<string> GetDefaultAvatarETag();

+

+        /// <summary>

         /// Get the default avatar.

         /// </summary>

         Task<AvatarInfo> GetDefaultAvatar();

@@ -83,6 +90,15 @@ namespace Timeline.Services
     public interface IUserAvatarService

     {

         /// <summary>

+        /// Get the etag of a user's avatar.

+        /// </summary>

+        /// <param name="username">The username of the user to get avatar etag of.</param>

+        /// <returns>The etag.</returns>

+        /// <exception cref="ArgumentException">Thrown if <paramref name="username"/> is null or empty.</exception>

+        /// <exception cref="UserNotExistException">Thrown if the user does not exist.</exception>

+        Task<string> GetAvatarETag(string username);

+

+        /// <summary>

         /// Get avatar of a user. If the user has no avatar, a default one is returned.

         /// </summary>

         /// <param name="username">The username of the user to get avatar of.</param>

@@ -107,22 +123,46 @@ namespace Timeline.Services
     {

         private readonly IHostingEnvironment _environment;

 

-        public DefaultUserAvatarProvider(IHostingEnvironment environment)

+        private readonly IETagGenerator _eTagGenerator;

+

+        private byte[] _cacheData;

+        private DateTime _cacheLastModified;

+        private string _cacheETag;

+

+        public DefaultUserAvatarProvider(IHostingEnvironment environment, IETagGenerator eTagGenerator)

         {

             _environment = environment;

+            _eTagGenerator = eTagGenerator;

         }

 

-        public async Task<AvatarInfo> GetDefaultAvatar()

+        private async Task CheckAndInit()

         {

+            if (_cacheData != null)

+                return;

+

             var path = Path.Combine(_environment.ContentRootPath, "default-avatar.png");

+            _cacheData = await File.ReadAllBytesAsync(path);

+            _cacheLastModified = File.GetLastWriteTime(path);

+            _cacheETag = _eTagGenerator.Generate(_cacheData);

+        }

+

+        public async Task<string> GetDefaultAvatarETag()

+        {

+            await CheckAndInit();

+            return _cacheETag;

+        }

+

+        public async Task<AvatarInfo> GetDefaultAvatar()

+        {

+            await CheckAndInit();

             return new AvatarInfo

             {

                 Avatar = new Avatar

                 {

                     Type = "image/png",

-                    Data = await File.ReadAllBytesAsync(path)

+                    Data = _cacheData

                 },

-                LastModified = File.GetLastWriteTime(path)

+                LastModified = _cacheLastModified

             };

         }

     }

@@ -161,12 +201,36 @@ namespace Timeline.Services
         private readonly IDefaultUserAvatarProvider _defaultUserAvatarProvider;

         private readonly IUserAvatarValidator _avatarValidator;

 

-        public UserAvatarService(ILogger<UserAvatarService> logger, DatabaseContext database, IDefaultUserAvatarProvider defaultUserAvatarProvider, IUserAvatarValidator avatarValidator)

+        private readonly IETagGenerator _eTagGenerator;

+

+        public UserAvatarService(

+            ILogger<UserAvatarService> logger,

+            DatabaseContext database,

+            IDefaultUserAvatarProvider defaultUserAvatarProvider,

+            IUserAvatarValidator avatarValidator,

+            IETagGenerator eTagGenerator)

         {

             _logger = logger;

             _database = database;

             _defaultUserAvatarProvider = defaultUserAvatarProvider;

             _avatarValidator = avatarValidator;

+            _eTagGenerator = eTagGenerator;

+        }

+

+        public async Task<string> GetAvatarETag(string username)

+        {

+            if (string.IsNullOrEmpty(username))

+                throw new ArgumentException("Username is null or empty.", nameof(username));

+

+            var userId = await _database.Users.Where(u => u.Name == username).Select(u => u.Id).SingleOrDefaultAsync();

+            if (userId == 0)

+                throw new UserNotExistException(username);

+

+            var eTag = (await _database.UserAvatars.Where(a => a.UserId == userId).Select(a => new { a.ETag }).SingleAsync()).ETag;

+            if (eTag == null)

+                return await _defaultUserAvatarProvider.GetDefaultAvatarETag();

+            else

+                return eTag;

         }

 

         public async Task<AvatarInfo> GetAvatar(string username)

@@ -174,16 +238,17 @@ namespace Timeline.Services
             if (string.IsNullOrEmpty(username))

                 throw new ArgumentException("Username is null or empty.", nameof(username));

 

-            var user = await _database.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

-            if (user == null)

+            var userId = await _database.Users.Where(u => u.Name == username).Select(u => u.Id).SingleOrDefaultAsync();

+            if (userId == 0)

                 throw new UserNotExistException(username);

 

-            await _database.Entry(user).Reference(u => u.Avatar).LoadAsync();

-            var avatar = user.Avatar;

+            var avatar = await _database.UserAvatars.Where(a => a.UserId == userId).Select(a => new { a.Type, a.Data, a.LastModified }).SingleAsync();

 

-            if ((avatar.Type == null) == (avatar.Data == null))

+            if ((avatar.Type == null) != (avatar.Data == null))

+            {

                 _logger.LogCritical("Database corupted! One of type and data of a avatar is null but the other is not.");

-                // TODO: Throw an exception to indicate this.

+                throw new DatabaseCorruptedException();

+            }

 

             if (avatar.Data == null)

             {

@@ -218,12 +283,11 @@ namespace Timeline.Services
                     throw new ArgumentException("Data of avatar is null.", nameof(avatar));

             }

 

-            var user = await _database.Users.Where(u => u.Name == username).SingleOrDefaultAsync();

-            if (user == null)

+            var userId = await _database.Users.Where(u => u.Name == username).Select(u => u.Id).SingleOrDefaultAsync();

+            if (userId == 0)

                 throw new UserNotExistException(username);

 

-            await _database.Entry(user).Reference(u => u.Avatar).LoadAsync();

-            var avatarEntity = user.Avatar;

+            var avatarEntity = await _database.UserAvatars.Where(a => a.UserId == userId).SingleAsync();

 

             if (avatar == null)

             {

@@ -233,6 +297,7 @@ namespace Timeline.Services
                 {

                     avatarEntity.Data = null;

                     avatarEntity.Type = null;

+                    avatarEntity.ETag = null;

                     avatarEntity.LastModified = DateTime.Now;

                     await _database.SaveChangesAsync();

                     _logger.LogInformation("Updated an entry in user_avatars.");

@@ -243,6 +308,7 @@ namespace Timeline.Services
                 await _avatarValidator.Validate(avatar);

                 avatarEntity.Type = avatar.Type;

                 avatarEntity.Data = avatar.Data;

+                avatarEntity.ETag = _eTagGenerator.Generate(avatar.Data);

                 avatarEntity.LastModified = DateTime.Now;

                 await _database.SaveChangesAsync();

                 _logger.LogInformation("Updated an entry in user_avatars.");

@@ -254,6 +320,7 @@ namespace Timeline.Services
     {

         public static void AddUserAvatarService(this IServiceCollection services)

         {

+            services.TryAddTransient<IETagGenerator, ETagGenerator>();

             services.AddScoped<IUserAvatarService, UserAvatarService>();

             services.AddSingleton<IDefaultUserAvatarProvider, DefaultUserAvatarProvider>();

             services.AddSingleton<IUserAvatarValidator, UserAvatarValidator>();