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Hazelcast C++ Client
Hazelcast C++ Client Library
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Hazelcast C++ Client
Hazelcast C++ Client Library
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A cluster-wide unique ID generator. More...
#include <flake_id_generator.h>
Inheritance diagram for hazelcast::client::flake_id_generator:Static Public Attributes | |
| static constexpr const char * | SERVICE_NAME = "hz:impl:flakeIdGeneratorService" |
Friends | |
| class | spi::ProxyManager |
A cluster-wide unique ID generator.
Generated IDs are
primitive values and are k-ordered (roughly ordered). IDs are in the range from
to
.
The IDs contain timestamp component and a node ID component, which is assigned when the member joins the cluster. This allows the IDs to be ordered and unique without any coordination between members, which makes the generator safe even in split-brain scenario (for caveats, see here).
Timestamp component is in milliseconds since 1.1.2018, 0:00 UTC and has 41 bits. This caps the useful lifespan of the generator to little less than 70 years (until ~2088). The sequence component is 6 bits. If more than 64 IDs are requested in single millisecond, IDs will gracefully overflow to the next millisecond and uniqueness is guaranteed in this case. The implementation does not allow overflowing by more than 15 seconds, if IDs are requested at higher rate, the call will block. Note, however, that clients are able to generate even faster because each call goes to a different (random) member and the 64 IDs/ms limit is for single member.
Node ID component of the ID has 16 bits. Members with member list join version higher than 2^16 won't be able to generate IDs, but functionality will be preserved by forwarding to another member. It is possible to generate IDs on any member or client as long as there is at least one member with join version smaller than 2^16 in the cluster. The remedy is to restart the cluster: nodeId will be assigned from zero again. Uniqueness after the restart will be preserved thanks to the timestamp component.
Definition at line 52 of file flake_id_generator.h.
1.9.1 