private static void LockTasks(List <ScheduledTask> tasks, IDbConnection db, IDbTransaction t)
{
const string sql = @"
UPDATE ScheduledTask
SET
LockedAt = @Now,
LockedBy = @User
WHERE Id IN
@Ids
";
var now = DateTime.Now;
var user = LockedIdentity.Get();
db.Execute(sql, new
{
Now = now,
Ids = tasks.Select(task => task.Id),
User = user
}, t);
foreach (var task in tasks)
{
task.LockedAt = now;
task.LockedBy = user;
}
}
public IList <ScheduledTask> GetAndLockNextAvailable(int readAhead)
{
var all = _tasks.SelectMany(t => t.Value);
// None locked, failed or succeeded, must be due, ordered by due time then priority
var now = DateTimeOffset.UtcNow;
var query = all
.Where(t => !t.FailedAt.HasValue && !t.SucceededAt.HasValue && !t.LockedAt.HasValue)
.Where(t => t.RunAt <= now)
.OrderBy(t => t.RunAt)
.ThenBy(t => t.Priority);
var tasks = query.Count() > readAhead?query.Take(readAhead).ToList() : query.ToList();
// Lock tasks:
if (tasks.Any())
{
foreach (ScheduledTask scheduledTask in tasks)
{
scheduledTask.LockedAt = now;
scheduledTask.LockedBy = LockedIdentity.Get();
}
}
return(tasks);
}