The 'Job' field has a null or empty value in Hangfire

Question

In Startup.cs I tried to enqueue recurring job like this:

RecurringJob.AddOrUpdate(() => Console.WriteLine("test"), Cron.Daily);

but received the error:

Please help to figure out what I'm doing wrong.

My configuration:

    //HangFire
    services.AddHangfire(configuration => configuration
      .SetDataCompatibilityLevel(CompatibilityLevel.Version_170)
      .UseSimpleAssemblyNameTypeSerializer()
      .UseRecommendedSerializerSettings()
      .UseSqlServerStorage(Configuration.GetConnectionString("HangfireConnection"),
          new SqlServerStorageOptions
          {
              CommandBatchMaxTimeout = TimeSpan.FromMinutes(5),
              SlidingInvisibilityTimeout = TimeSpan.FromMinutes(5),
              QueuePollInterval = TimeSpan.Zero,
              UseRecommendedIsolationLevel = true,
              DisableGlobalLocks = true,
          }
      ));

P.S. although 'fire and forget' jobs works.

Answer 1

Hangfire's source indicates that this exception (and message) is thrown when the expression !recurringJob.ContainsKey("Job") || String.IsNullOrWhiteSpace(recurringJob["Job"]) is true.

try
{
    if (!recurringJob.ContainsKey("Job") || String.IsNullOrWhiteSpace(recurringJob["Job"]))
    {
        throw new InvalidOperationException("The 'Job' field has a null or empty value");
    }

    Job = InvocationData.DeserializePayload(recurringJob["Job"]).DeserializeJob();
}
catch (Exception ex)
{
    _errors.Add(ex);
}

The recurringJob Dictionary gets set by the method GetAllEntriesFromHash:

public override Dictionary<string, string> GetAllEntriesFromHash(string key)
{
    if (key == null) throw new ArgumentNullException(nameof(key));

    return _storage.UseConnection(_dedicatedConnection, connection =>
    {
        var result = connection.Query<SqlHash>(
            $"select Field, Value from [{_storage.SchemaName}].Hash with (forceseek, readcommittedlock) where [Key] = @key",
            new { key },
            commandTimeout: _storage.CommandTimeout)
            .ToDictionary(x => x.Field, x => x.Value);

        return result.Count != 0 ? result : null;
    });
}

So what is probably happening is the GetAllEntriesFromHash method is returning null, or a Dictionary that doesn't contain the key Job (or it's null/whitespace). But, in a thread, a Hangfire Contributor commented:

That's not even a problem, just ignore those exceptions or tell Visual Studio to not to break on them. Hangfire handles a lot of exceptions, and may generate tons of OperationCanceledException during shutdown that tells all the background processes that shutdown was requested.

Thus, it seems like this error can be ignored.