Achieving absolute ordering on JPA event-entities











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I try to define immutable Event-Entites (Event Sourcing) using Java JPA/Hibernate and want those events to have an absolute ordering that already is defined right after object-creation, before any persistence has taken place (no distributed setup where one would need consensus)



We are using automatic auditing properties using @CreatedDate but I crossed that off my list since this is only populated during persistence.



I can think of 2 options:




  1. using a global database-sequence that is queried during object-creation


  2. Long ordering = System.nanoTime()


any advice/idea appreciated.










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    up vote
    0
    down vote

    favorite












    I try to define immutable Event-Entites (Event Sourcing) using Java JPA/Hibernate and want those events to have an absolute ordering that already is defined right after object-creation, before any persistence has taken place (no distributed setup where one would need consensus)



    We are using automatic auditing properties using @CreatedDate but I crossed that off my list since this is only populated during persistence.



    I can think of 2 options:




    1. using a global database-sequence that is queried during object-creation


    2. Long ordering = System.nanoTime()


    any advice/idea appreciated.










    share|improve this question


























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I try to define immutable Event-Entites (Event Sourcing) using Java JPA/Hibernate and want those events to have an absolute ordering that already is defined right after object-creation, before any persistence has taken place (no distributed setup where one would need consensus)



      We are using automatic auditing properties using @CreatedDate but I crossed that off my list since this is only populated during persistence.



      I can think of 2 options:




      1. using a global database-sequence that is queried during object-creation


      2. Long ordering = System.nanoTime()


      any advice/idea appreciated.










      share|improve this question















      I try to define immutable Event-Entites (Event Sourcing) using Java JPA/Hibernate and want those events to have an absolute ordering that already is defined right after object-creation, before any persistence has taken place (no distributed setup where one would need consensus)



      We are using automatic auditing properties using @CreatedDate but I crossed that off my list since this is only populated during persistence.



      I can think of 2 options:




      1. using a global database-sequence that is queried during object-creation


      2. Long ordering = System.nanoTime()


      any advice/idea appreciated.







      java hibernate sorting jpa event-sourcing






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Nov 23 at 1:13









      Aleksandr Semyannikov

      556216




      556216










      asked Nov 22 at 16:40









      hotzen

      1,5691636




      1,5691636
























          1 Answer
          1






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          down vote














          want those events to have an absolute ordering that already is defined
          right after object-creation






          1. The simpliest solution is like:



            public class SomeEntity {
            private LocalDateTime createdAt = LocalDateTime.now();
            }


            Of course it is possible that two objects will be created simultaneously and will have the same date, but it might be extremely hard to get.




          2. A bit more complex - ordered by id if dates are equal and both objects are persisted. There may be indeterminacy if some of objects is not persisted yet, but if both are persisted - strict order is guaranteed:



            public class SomeEntity implements Comparable<SomeEntity> {

            private Long id;

            private LocalDateTime createdAt = LocalDateTime.now();

            @Override
            public int compareTo(SomeEntity o) {
            int result = createdAt.compareTo(o.createdAt);
            if (result == 0) {
            if (id != null && o.id != null) {
            result = id.compareTo(o.id);
            } else if (id != null) {
            result = 1;
            } else if (o.id != null) {
            result = -1;
            }
            }
            return result;
            }
            }



          3. The most complex option but strict ordering is guaranteed: you can create counter service in your JVM and create events through factory, that will use that counter during event creation.



            public class CounterService {
            AtomicInteger counter = new AtomicInteger();
            public int getNext() {
            return counter.incrementAndGet();
            }
            }

            public class SomeEntityFactory {
            private CounterService counterService;

            public SomeEntity create() {
            return new SomeEntity(counterService.getNext());
            }
            }

            public class SomeEntity {
            private int order;

            SomeEntity(int order) {
            this.order = order;
            }
            }


            Of course, this is example only, counter service might return BigInteger and be a web service, for instance. Or you can use a database sequence like a counter.








          share|improve this answer























          • i am hesistant to use the wall-clock time (LocalDateTime.now()).
            – hotzen
            Nov 23 at 13:15










          • the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
            – hotzen
            Nov 23 at 13:16










          • There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
            – Aleksandr Semyannikov
            Nov 23 at 13:28










          • @hotzen I changed code in the second solution a little.
            – Aleksandr Semyannikov
            Nov 23 at 13:48










          • i am hesistant because of time skew (even if ntp)
            – hotzen
            Nov 30 at 8:22











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          up vote
          1
          down vote














          want those events to have an absolute ordering that already is defined
          right after object-creation






          1. The simpliest solution is like:



            public class SomeEntity {
            private LocalDateTime createdAt = LocalDateTime.now();
            }


            Of course it is possible that two objects will be created simultaneously and will have the same date, but it might be extremely hard to get.




          2. A bit more complex - ordered by id if dates are equal and both objects are persisted. There may be indeterminacy if some of objects is not persisted yet, but if both are persisted - strict order is guaranteed:



            public class SomeEntity implements Comparable<SomeEntity> {

            private Long id;

            private LocalDateTime createdAt = LocalDateTime.now();

            @Override
            public int compareTo(SomeEntity o) {
            int result = createdAt.compareTo(o.createdAt);
            if (result == 0) {
            if (id != null && o.id != null) {
            result = id.compareTo(o.id);
            } else if (id != null) {
            result = 1;
            } else if (o.id != null) {
            result = -1;
            }
            }
            return result;
            }
            }



          3. The most complex option but strict ordering is guaranteed: you can create counter service in your JVM and create events through factory, that will use that counter during event creation.



            public class CounterService {
            AtomicInteger counter = new AtomicInteger();
            public int getNext() {
            return counter.incrementAndGet();
            }
            }

            public class SomeEntityFactory {
            private CounterService counterService;

            public SomeEntity create() {
            return new SomeEntity(counterService.getNext());
            }
            }

            public class SomeEntity {
            private int order;

            SomeEntity(int order) {
            this.order = order;
            }
            }


            Of course, this is example only, counter service might return BigInteger and be a web service, for instance. Or you can use a database sequence like a counter.








          share|improve this answer























          • i am hesistant to use the wall-clock time (LocalDateTime.now()).
            – hotzen
            Nov 23 at 13:15










          • the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
            – hotzen
            Nov 23 at 13:16










          • There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
            – Aleksandr Semyannikov
            Nov 23 at 13:28










          • @hotzen I changed code in the second solution a little.
            – Aleksandr Semyannikov
            Nov 23 at 13:48










          • i am hesistant because of time skew (even if ntp)
            – hotzen
            Nov 30 at 8:22















          up vote
          1
          down vote














          want those events to have an absolute ordering that already is defined
          right after object-creation






          1. The simpliest solution is like:



            public class SomeEntity {
            private LocalDateTime createdAt = LocalDateTime.now();
            }


            Of course it is possible that two objects will be created simultaneously and will have the same date, but it might be extremely hard to get.




          2. A bit more complex - ordered by id if dates are equal and both objects are persisted. There may be indeterminacy if some of objects is not persisted yet, but if both are persisted - strict order is guaranteed:



            public class SomeEntity implements Comparable<SomeEntity> {

            private Long id;

            private LocalDateTime createdAt = LocalDateTime.now();

            @Override
            public int compareTo(SomeEntity o) {
            int result = createdAt.compareTo(o.createdAt);
            if (result == 0) {
            if (id != null && o.id != null) {
            result = id.compareTo(o.id);
            } else if (id != null) {
            result = 1;
            } else if (o.id != null) {
            result = -1;
            }
            }
            return result;
            }
            }



          3. The most complex option but strict ordering is guaranteed: you can create counter service in your JVM and create events through factory, that will use that counter during event creation.



            public class CounterService {
            AtomicInteger counter = new AtomicInteger();
            public int getNext() {
            return counter.incrementAndGet();
            }
            }

            public class SomeEntityFactory {
            private CounterService counterService;

            public SomeEntity create() {
            return new SomeEntity(counterService.getNext());
            }
            }

            public class SomeEntity {
            private int order;

            SomeEntity(int order) {
            this.order = order;
            }
            }


            Of course, this is example only, counter service might return BigInteger and be a web service, for instance. Or you can use a database sequence like a counter.








          share|improve this answer























          • i am hesistant to use the wall-clock time (LocalDateTime.now()).
            – hotzen
            Nov 23 at 13:15










          • the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
            – hotzen
            Nov 23 at 13:16










          • There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
            – Aleksandr Semyannikov
            Nov 23 at 13:28










          • @hotzen I changed code in the second solution a little.
            – Aleksandr Semyannikov
            Nov 23 at 13:48










          • i am hesistant because of time skew (even if ntp)
            – hotzen
            Nov 30 at 8:22













          up vote
          1
          down vote










          up vote
          1
          down vote










          want those events to have an absolute ordering that already is defined
          right after object-creation






          1. The simpliest solution is like:



            public class SomeEntity {
            private LocalDateTime createdAt = LocalDateTime.now();
            }


            Of course it is possible that two objects will be created simultaneously and will have the same date, but it might be extremely hard to get.




          2. A bit more complex - ordered by id if dates are equal and both objects are persisted. There may be indeterminacy if some of objects is not persisted yet, but if both are persisted - strict order is guaranteed:



            public class SomeEntity implements Comparable<SomeEntity> {

            private Long id;

            private LocalDateTime createdAt = LocalDateTime.now();

            @Override
            public int compareTo(SomeEntity o) {
            int result = createdAt.compareTo(o.createdAt);
            if (result == 0) {
            if (id != null && o.id != null) {
            result = id.compareTo(o.id);
            } else if (id != null) {
            result = 1;
            } else if (o.id != null) {
            result = -1;
            }
            }
            return result;
            }
            }



          3. The most complex option but strict ordering is guaranteed: you can create counter service in your JVM and create events through factory, that will use that counter during event creation.



            public class CounterService {
            AtomicInteger counter = new AtomicInteger();
            public int getNext() {
            return counter.incrementAndGet();
            }
            }

            public class SomeEntityFactory {
            private CounterService counterService;

            public SomeEntity create() {
            return new SomeEntity(counterService.getNext());
            }
            }

            public class SomeEntity {
            private int order;

            SomeEntity(int order) {
            this.order = order;
            }
            }


            Of course, this is example only, counter service might return BigInteger and be a web service, for instance. Or you can use a database sequence like a counter.








          share|improve this answer















          want those events to have an absolute ordering that already is defined
          right after object-creation






          1. The simpliest solution is like:



            public class SomeEntity {
            private LocalDateTime createdAt = LocalDateTime.now();
            }


            Of course it is possible that two objects will be created simultaneously and will have the same date, but it might be extremely hard to get.




          2. A bit more complex - ordered by id if dates are equal and both objects are persisted. There may be indeterminacy if some of objects is not persisted yet, but if both are persisted - strict order is guaranteed:



            public class SomeEntity implements Comparable<SomeEntity> {

            private Long id;

            private LocalDateTime createdAt = LocalDateTime.now();

            @Override
            public int compareTo(SomeEntity o) {
            int result = createdAt.compareTo(o.createdAt);
            if (result == 0) {
            if (id != null && o.id != null) {
            result = id.compareTo(o.id);
            } else if (id != null) {
            result = 1;
            } else if (o.id != null) {
            result = -1;
            }
            }
            return result;
            }
            }



          3. The most complex option but strict ordering is guaranteed: you can create counter service in your JVM and create events through factory, that will use that counter during event creation.



            public class CounterService {
            AtomicInteger counter = new AtomicInteger();
            public int getNext() {
            return counter.incrementAndGet();
            }
            }

            public class SomeEntityFactory {
            private CounterService counterService;

            public SomeEntity create() {
            return new SomeEntity(counterService.getNext());
            }
            }

            public class SomeEntity {
            private int order;

            SomeEntity(int order) {
            this.order = order;
            }
            }


            Of course, this is example only, counter service might return BigInteger and be a web service, for instance. Or you can use a database sequence like a counter.









          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Nov 23 at 13:48

























          answered Nov 22 at 17:25









          Aleksandr Semyannikov

          556216




          556216












          • i am hesistant to use the wall-clock time (LocalDateTime.now()).
            – hotzen
            Nov 23 at 13:15










          • the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
            – hotzen
            Nov 23 at 13:16










          • There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
            – Aleksandr Semyannikov
            Nov 23 at 13:28










          • @hotzen I changed code in the second solution a little.
            – Aleksandr Semyannikov
            Nov 23 at 13:48










          • i am hesistant because of time skew (even if ntp)
            – hotzen
            Nov 30 at 8:22


















          • i am hesistant to use the wall-clock time (LocalDateTime.now()).
            – hotzen
            Nov 23 at 13:15










          • the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
            – hotzen
            Nov 23 at 13:16










          • There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
            – Aleksandr Semyannikov
            Nov 23 at 13:28










          • @hotzen I changed code in the second solution a little.
            – Aleksandr Semyannikov
            Nov 23 at 13:48










          • i am hesistant because of time skew (even if ntp)
            – hotzen
            Nov 30 at 8:22
















          i am hesistant to use the wall-clock time (LocalDateTime.now()).
          – hotzen
          Nov 23 at 13:15




          i am hesistant to use the wall-clock time (LocalDateTime.now()).
          – hotzen
          Nov 23 at 13:15












          the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
          – hotzen
          Nov 23 at 13:16




          the CounterService would always start from 0, so this would need to be persistant. then one could use a database-sequence right-away. isnt it?
          – hotzen
          Nov 23 at 13:16












          There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
          – Aleksandr Semyannikov
          Nov 23 at 13:28




          There is a plenty of options with counter, I wrote it just for example. DB sequence is just another representation of that approach. Please, clerify for me why are you hesistant to use LocalDateTime? I know that there are some aspects you need to pay attention to, e.g. timezones, but it can be solved. What precision do you need?
          – Aleksandr Semyannikov
          Nov 23 at 13:28












          @hotzen I changed code in the second solution a little.
          – Aleksandr Semyannikov
          Nov 23 at 13:48




          @hotzen I changed code in the second solution a little.
          – Aleksandr Semyannikov
          Nov 23 at 13:48












          i am hesistant because of time skew (even if ntp)
          – hotzen
          Nov 30 at 8:22




          i am hesistant because of time skew (even if ntp)
          – hotzen
          Nov 30 at 8:22


















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