Sequence number
A sequence number is a value or identifier associated with an ordered sequence or its items to indicate position, order, or sequence identity.
Akka in Action, Second Edition
A sequence number is an ascending ordinal identifying an event's position within an entity's event stream.
- How it is used
- Identifies an entity’s event position and supports resuming journal consumption.
- How deep it goes
- Defines per-entity numbering, contrasts it with global ordering, and connects it to query offsets and ranges.
- Examples
- Uses cargo events for containers 9 and 11, journal tables, tagged reads, and an EventEnvelope containing sequence value 1.
- What you can do after
- Apply it via Akka Persistence Query to start from no offset or continue from a recorded journal position.
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Acing the CCNA Exam: Volume 2 Advanced Networking and Security
A sequence number is an ordinal value attached to a message to identify its position in a sequence of messages.
- How it is used
- Identifies the order of Syslog messages for interpreting device-generated logs.
- How deep it goes
- Defines placement, optionality, defaults, and activation behavior but does not detail sequence-number generation internals.
- Examples
- Uses the numbered message 000065 and the service sequence-numbers global configuration command.
- What you can do after
- Configure sequence numbers for future Syslog messages with Cisco IOS global configuration.
Read how Acing the CCNA Exam: Volume 2 Advanced Networking and Security explains sequence number →
Apache Kafka in Action
A sequence ID is an ordered identifier assigned to a Kafka message to detect duplicates and verify message order within a partition.
- How it is used
- Supports exactly-once producer delivery by identifying duplicate, missing, or out-of-order messages within a partition.
- How deep it goes
- Explains producer and broker checks, ACK/NACK responses, required settings, and partition scope without detailing internal sequence-number encoding.
- Examples
- Uses an idempotent console producer, a lost-acknowledgment duplicate, and an out-of-order message rejected with a NACK.
- What you can do after
- Diagnose/debug with it: identify duplicate and ordering failures, then verify idempotence settings and partition placement.
Related concepts
- syslog messagepart of · A Syslog message is a structured event record generated by a device or one of its services to report an occurrence or status change.
- idempotencyimplements · Idempotency is the property of an operation whereby repeating it has the same effective result or externally observable effect as performing it once.
- Domain Storytellingpart of · Domain Storytelling is a collaborative modeling technique that captures domain knowledge through visual stories of actors, activities, objects, and interactions in a process.
- vertical data formatused by · A vertical data format represents sequence data by storing occurrences with their sequence identifiers and element positions rather than storing complete sequences horizontally.
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