Error: NameResolutionFailure

Jules · July 17, 2018, 7:07am

Hi folks,

Duplicati went well for a couple of weeks. The last 2 updates broke my 2 running backups. The last one has done it for me completely. How to fix this?

Error: NameResolutionFailure

Fatal error
System.Net.WebException: Error: NameResolutionFailure
  at System.Net.WebConnection+<Connect>d__16.MoveNext () [0x00044] in <fc308f916aec4e4283e0c1d4b761760a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0003e] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult () [0x00000] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Net.WebConnection+<InitConnection>d__19.MoveNext () [0x000cc] in <fc308f916aec4e4283e0c1d4b761760a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0003e] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in <71d8ad678db34313b7f718a414dfcb25>:0 
  at System.Net.WebOperation+<Run>d__57.MoveNext () [0x0009a] in <fc308f916aec4e4283e0c1d4b761760a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Net.WebCompletionSource`1+<WaitForCompletion>d__15[T].MoveNext () [0x00094] in <fc308f916aec4e4283e0c1d4b761760a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Net.HttpWebRequest+<RunWithTimeoutWorker>d__244`1[T].MoveNext () [0x000ba] in <fc308f916aec4e4283e0c1d4b761760a>:0 
--- End of stack trace from previous location where exception was thrown ---
  at Duplicati.Library.Main.BackendManager.List () [0x00049] in <ae134c5a9abb455eb7f06c134d211773>:0 
  at Duplicati.Library.Main.Operation.FilelistProcessor.RemoteListAnalysis (Duplicati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options options, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Main.IBackendWriter log, System.String protectedfile) [0x0000d] in <ae134c5a9abb455eb7f06c134d211773>:0 
  at Duplicati.Library.Main.Operation.FilelistProcessor.VerifyRemoteList (Duplicati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options options, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Main.IBackendWriter log, System.String protectedfile) [0x00000] in <ae134c5a9abb455eb7f06c134d211773>:0 
  at Duplicati.Library.Main.Operation.BackupHandler.PreBackupVerify (Duplicati.Library.Main.BackendManager backend, System.String protectedfile) [0x000fd] in <ae134c5a9abb455eb7f06c134d211773>:0 
  at Duplicati.Library.Main.Operation.BackupHandler.Run (System.String[] sources, Duplicati.Library.Utility.IFilter filter) [0x003c6] in <ae134c5a9abb455eb7f06c134d211773>:10

Jules · July 19, 2018, 12:23pm

Bump.

No one?

What I’ve done until now:

deleted & reinstalled the application
deleted & remade the jobs - does not work.

JonMikelV · July 21, 2018, 2:44pm

Hi @Jules, welcome to the forum!

It would help if we know what version of Dupliati you are running and on what OS (Linux, MacOS, Windows) - but usually that NameResolutionFailure error happens on Linux/MacOS so I’m going to assume you’re using one of those for now. (Here are some similar issues mentioned by other users Search results for ‘NameResolutionFailure’ - Duplicati).

Can you try running ping localhost in a terminal window? You should see something like “Reply from…” repeated a number of times (you can use ctrl-c to stop it).

If you DON’T get a “Reply from…” response, then you mist likely need to add 127.0.0.1 localhost to your /etc/hosts file.

Of course you had Duplicati running fine for a while so unless something else has removed localhost from your hosts file I’m not sure why this would have started happening, so please let us know whether or not this helps you out.

(By the way, I edited your original post by adding “~~~” before and after the error message to make it easier to read.)

ech · August 14, 2019, 10:46am

I’m seeing this now - had no problem like this with the version I’m running until today, and “ping localhost” returns 127.0.0.1 just fine… it happens after the “verifying backend” has been showing on the top of the web ui for a few minutes. The backend is B2 backblaze.

This is in Fedora 30, version 2.0.4.21_experimental_2019-06-28. And restarting the service doesn’t break anything - it comes up fine.

My router has been up for 9 days w/o incident and I don’t see any errors there regarding dns-related problems. Restarting the duplicati service doesn’t cause any immediate error, but it doesn’t fix things either. Still get something similar to the error logged above, with unfortunately no indication of what hostname lookup is failing.

Here’s the log entry:

System.Net.WebException: Error: NameResolutionFailure
  at System.Net.WebConnection.Connect (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x00079] in <cae6d5d40bdb48e7919fce5039029dd1>:0 
  at System.Net.WebConnection.InitConnection (System.Net.WebOperation operation, System.Threading.CancellationToken cancellationToken) [0x000f7] in <cae6d5d40bdb48e7919fce5039029dd1>:0 
  at System.Net.WebOperation.Run () [0x000b7] in <cae6d5d40bdb48e7919fce5039029dd1>:0 
  at System.Net.WebCompletionSource`1[T].WaitForCompletion () [0x000b1] in <cae6d5d40bdb48e7919fce5039029dd1>:0 
  at System.Net.HttpWebRequest.RunWithTimeoutWorker[T] (System.Threading.Tasks.Task`1[TResult] workerTask, System.Int32 timeout, System.Action abort, System.Func`1[TResult] aborted, System.Threading.CancellationTokenSource cts) [0x00118] in <cae6d5d40bdb48e7919fce5039029dd1>:0 
  at Duplicati.Library.Main.BackendManager.List () [0x00049] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Operation.FilelistProcessor.RemoteListAnalysis (Duplicati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options options, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Main.IBackendWriter log, System.String protectedfile) [0x0000d] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Operation.FilelistProcessor.VerifyRemoteList (Duplicati.Library.Main.BackendManager backend, Duplicati.Library.Main.Options options, Duplicati.Library.Main.Database.LocalDatabase database, Duplicati.Library.Main.IBackendWriter log, System.String protectedfile) [0x00000] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Operation.BackupHandler.PreBackupVerify (Duplicati.Library.Main.BackendManager backend, System.String protectedfile) [0x0010d] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Operation.BackupHandler.RunAsync (System.String[] sources, Duplicati.Library.Utility.IFilter filter) [0x0103a] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at CoCoL.ChannelExtensions.WaitForTaskOrThrow (System.Threading.Tasks.Task task) [0x00050] in <6973ce2780de4b28aaa2c5ffc59993b1>:0 
  at Duplicati.Library.Main.Operation.BackupHandler.Run (System.String[] sources, Duplicati.Library.Utility.IFilter filter) [0x00008] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Controller+<>c__DisplayClass13_0.<Backup>b__0 (Duplicati.Library.Main.BackupResults result) [0x00035] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Controller.RunAction[T] (T result, System.String[]& paths, Duplicati.Library.Utility.IFilter& filter, System.Action`1[T] method) [0x00271] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Library.Main.Controller.Backup (System.String[] inputsources, Duplicati.Library.Utility.IFilter filter) [0x00068] in <0f9596a4606a4cc196eb7582e49cc580>:0 
  at Duplicati.Server.Runner.Run (Duplicati.Server.Runner+IRunnerData data, System.Boolean fromQueue) [0x002f7] in <5ee414afc7e943419837effe11774b4a>:0

Jules · August 14, 2019, 1:34pm

An updated version fixed the problem somehow.

Thank you for looking into this for me.

Thread closed.

ech · August 14, 2019, 9:43pm

I’m using a relatively recent version, and it only just started failing today, having changed nothing else that I can see that would be related to the failure… so not sure this should be closed.

Or maybe I should open another thread?

Or maybe I just had to wait a few more hours… as the problem is now gone and my backup is working again. Hmmm. Not a satisfying fix.

Jules · August 16, 2019, 6:57am

I’ve marked the thread as no solution as there seems to be some others with the same problem.

Alvin · December 29, 2020, 3:05pm

I have the same issue. It threw the error message today. I added 127.0.0.1 localhost to /etc/hosts file.
It fixed the problem.

ts678 · December 29, 2020, 4:58pm

Welcome to the forum @Alvin

Surprising. I guess that’s a reminder not to count on basic things being set up the way one might think.

Thanks for the hint.