/// <summary>
/// Asynchronously adds a log to storage
/// </summary>
/// <param name="channelName">The name of the channel associated with the log</param>
/// <param name="log">The log to add</param>
/// <exception cref="StorageException"/>
public Task PutLog(string channelName, Log log)
{
return(AddTaskToQueue(() =>
{
var logJsonString = LogSerializer.Serialize(log);
var maxSize = _storageAdapter.GetMaxStorageSize();
var logSize = Encoding.UTF8.GetBytes(logJsonString).Length;
if (maxSize < 0)
{
throw new StorageException("Failed to store a log to the database.");
}
if (maxSize <= logSize)
{
throw new StorageException($"Log is too large ({logSize} bytes) to store in database. " +
$"Current maximum database size is {maxSize} bytes.");
}
while (true)
{
try
{
_storageAdapter.Insert(TableName,
new[] { ColumnChannelName, ColumnLogName },
new List <object[]> {
new object[] { channelName, logJsonString }
});
return;
}
catch (StorageFullException)
{
var oldestLog = _storageAdapter.Select(TableName, ColumnChannelName, channelName, string.Empty, null, 1, new string[] { ColumnIdName });
if (oldestLog != null && oldestLog.Count > 0 && oldestLog[0].Length > 0)
{
_storageAdapter.Delete(TableName, ColumnIdName, oldestLog[0][0]);
}
else
{
throw new StorageException("Failed to add a new log. Storage is full and old logs cannot be purged.");
}
}
}
}));
}
/// <summary>
/// Asynchronously retrieves logs from storage and flags them to avoid duplicate retrievals on subsequent calls
/// </summary>
/// <param name="channelName">Name of the channel to retrieve logs from</param>
/// <param name="limit">The maximum number of logs to retrieve</param>
/// <param name="logs">A list to which the retrieved logs will be added</param>
/// <returns>A batch ID for the set of returned logs; null if no logs are found</returns>
/// <exception cref="StorageException"/>
public Task <string> GetLogsAsync(string channelName, int limit, List <Log> logs)
{
return(AddTaskToQueue(() =>
{
logs?.Clear();
var retrievedLogs = new List <Log>();
AppCenterLog.Debug(AppCenterLog.LogTag,
$"Trying to get up to {limit} logs from storage for {channelName}");
var idPairs = new List <Tuple <Guid?, long> >();
var failedToDeserializeALog = false;
var objectEntries = _storageAdapter.Select(TableName, ColumnChannelName, channelName, ColumnIdName, _pendingDbIdentifiers.Cast <object>().ToArray(), limit);
var retrievedEntries = objectEntries.Select(entries =>
new LogEntry()
{
Id = (long)entries[0],
Channel = (string)entries[1],
Log = (string)entries[2]
}
).ToList();
foreach (var entry in retrievedEntries)
{
try
{
var log = LogSerializer.DeserializeLog(entry.Log);
retrievedLogs.Add(log);
idPairs.Add(Tuple.Create(log.Sid, Convert.ToInt64(entry.Id)));
}
catch (JsonException e)
{
AppCenterLog.Error(AppCenterLog.LogTag, "Cannot deserialize a log in storage", e);
failedToDeserializeALog = true;
_storageAdapter.Delete(TableName, ColumnIdName, entry.Id);
}
}
if (failedToDeserializeALog)
{
AppCenterLog.Warn(AppCenterLog.LogTag, "Deleted logs that could not be deserialized");
}
if (idPairs.Count == 0)
{
AppCenterLog.Debug(AppCenterLog.LogTag,
$"No available logs in storage for channel '{channelName}'");
return null;
}
// Process the results
var batchId = Guid.NewGuid().ToString();
ProcessLogIds(channelName, batchId, idPairs);
logs?.AddRange(retrievedLogs);
return batchId;
}));
}