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p

lerna.util

sequence

package sequence

Lerna Util Sequence

Overview

The package provides an ID generator.

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Type Members

  1. abstract class CassandraSequenceFactory extends SequenceFactory with AppLogging

    A sequence factory using Cassandra

    A sequence factory using Cassandra

    Overview

    • Manage sequences using (seqId,subId) as a key
    • Reduce overhead by generating and persisting sequence beforehand
    • For each key (seqId,subId), hold the next IDs in memory

    seqID concept is introduced by this implementation. It can be thought of as a sub-namespace.

    Details

    Define an increment value as max server count (name it n) beforehand. Assign the different initial values (that is in the range [1 to n]) to each server. We can generate a unique ID using the above condition.

    For example, suppose we have 3 servers initially and scale it out to 5 servers in the future.

    Assign initial values as follows

    • Server A: (Assign an initial value = 1)
    • Server B: (Assign an initial value = 2)
    • Server C: (Assign an initial value = 3)

    Each server generates a sequence like the below

    • Server A generates a sequence 1, 6, 11, ..., Ai = 1 + n * i
    • Server B generates a sequence 2, 7, 12, ..., Bi = 2 + n * i
    • Server C generates a sequence 3, 8, 13, ..., Ci = 3 + n * i

    In the future, we can add two servers (named Server D and Server E).

    • Server D is assigned 4 as an initial value. It generates a sequence 4, 9, 14, ..., Di = 4 + n * i.
    • Server E is assigned 5 as an initial value. It generates a sequence 5, 10, 15, ..., Ei = 5 + n * i.

    Therefore, as we see the above, we can generate unique IDs.

    Annotations
    @SuppressWarnings()
  2. trait SequenceFactory extends AnyRef

    A trait that provides generating ID sequence

    A trait that provides generating ID sequence

    A concrete implementation for this trait must behave like below.

    • Generate unique ID only for the given subID This means that IDs generated with different subID can be the same value. We can think subID as a namespace.
    • A Generated ID should be in the range [0, maxSequence] (both inclusive)

    Behaviors that are not described above are dependent on a concrete implementation.

  3. class SequenceFactoryCassandraConfig extends AnyRef

Value Members

  1. object FutureConverters

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