Different host instances, run for a period of time, the KEY sequence is inconsistent about idgen

[RobThree]

Are you sure (i.e. did you confirm) the _machineId differs on each machine?

static void Main(string[] args)
{
    var a = new IdGenerator(1, new IdGeneratorOptions(sequenceOverflowStrategy: SequenceOverflowStrategy.SpinWait));
    var b = new IdGenerator(2, new IdGeneratorOptions(sequenceOverflowStrategy: SequenceOverflowStrategy.SpinWait));

    for (int i = 0; i < 10; i++)
    {
        var a_id = a.CreateId();
        var b_id = b.CreateId();

        Console.WriteLine($"A: {a_id} {Convert.ToString(a_id, 2)}");
        Console.WriteLine($"B: {b_id} {Convert.ToString(b_id, 2)}");
    }
}

As you can see in the above screenshot the red part contains the _machineId (10 bits), the blue the sequence number (12 bits) and the green part the timestamp.

The values you show seem hand-crafted (probably to demonstrate the problem). Can you please show actual values?

[RobThree]

Oh, wait, nevermind. I think I understood the question wrong. I think I understand now. But I will still need actual generated values (and the corresponding generator (or "machine") id along with it) to see if there's an actual problem or not.

I think what you're seeing is correct. Only part of the ID is a timestamp. There's no guarantee the ID's are all sequential since the machines/generators don't communicate between eachother. The only 'guarantee' you have, concerning ID sequences, is that for a single generator, the values are sequential. IdGen also guarantees that there are no collisions (as long as no sequence overflows occur and machine/generator ID's are different where they need to be etc.) without actually having to coordinate the IdGenerators or requiring communication between those generators. So ID's generated by different generators (on different machines) may not be, and most likely won't be, 100% sequential.

[ArvinHsieh]

Oh, wait, nevermind. I think I understood the question wrong. I think I understand now. But I will still need actual generated values (and the corresponding generator (or "machine") id along with it) to see if there's an actual problem or not.

I think what you're seeing is correct. Only part of the ID is a timestamp. There's no guarantee the ID's are all sequential since the machines/generators don't communicate between eachother. The only 'guarantee' you have, concerning ID sequences, is that for a single generator, the values are sequential. IdGen also guarantees that there are no collisions (as long as no sequence overflows occur and machine/generator ID's are different where they need to be etc.) without actually having to coordinate the IdGenerators or requiring communication between those generators. So ID's generated by different generators (on different machines) may not be, and most likely won't be, 100% sequential.

Thank you for your explanation, the actual _machineId(GeneratorId) I use is 601/604, but if I want to ensure that the serial numbers generated are continuous in this scenario, is there any suggestion? For example, I need to store the ID generated each time in Redis and check whether they need to be regenerated. But this will have an impact on the generation speed for concurrent accesses.

Thanks for your reply.

[RobThree]

If you need sequential, "continuous", ID's then IdGen is not for you. IdGen is, as the first line in the documentation states: "... a low-latency, distributed, uncoordinated, (roughly) time ordered, compact and highly available Id generation system". For Id's to be continuous you always need some form of coordination.

[ArvinHsieh]

Ok, I understood. Thanks.