Fixes #47 - System.InvalidOperationException: Startup() can only be c…

…alled once

If WriteLog.Startup() fails, it can never be retried as startedAt will be populated. This allows for async writes to fail temporarily and then resume once the other process has released the lock on the metastore files.

src/Imazen.HybridCache/MetaStore/WriteLog.cs

@@ -18,6 +18,7 @@ internal class WriteLog
         private readonly MetaStoreOptions options;
         private readonly ILogger logger;
         private long startedAt;
+        private bool startupComplete;
         private FileStream writeLogStream;
         private BinaryWriter binaryLogWriter;
         private readonly object writeLock = new object();
@@ -67,10 +68,10 @@ private void CreateWriteLog(long startedAtTick)
             }
         }
 
-        // Returns a dictionary of the database
+        // Returns a dictionary of the database 
         public async Task<ConcurrentDictionary<string, CacheDatabaseRecord>> Startup()
         {
-            if (startedAt != 0) throw new InvalidOperationException("Startup() can only be called once");
+            if (startupComplete) throw new InvalidOperationException("Startup() can only be called once");
             startedAt = Stopwatch.GetTimestamp();
 
             if (!Directory.Exists(databaseDir))
@@ -200,6 +201,7 @@ public async Task<ConcurrentDictionary<string, CacheDatabaseRecord>> Startup()
                 diskBytes += dict.Values.Sum(r => r.DiskSize);
             }
 
+            startupComplete = true;
             return dict;
         }
 
@@ -246,7 +248,7 @@ private Task WriteLogEntry(LogEntry entry, bool flush)
             lock (writeLock)
             {
                 if (startedAt == 0)
-                    throw new InvalidOperationException("WriteLog cannot be used before calling ReadAll()");
+                    throw new InvalidOperationException("WriteLog cannot be used before calling Startup()");
                 if (writeLogStream == null)
                     throw new InvalidOperationException("WriteLog cannot be after StopAsync is called");
                 var startPos = writeLogStream.Position;