Glossary · System coordination, integration and orchestration
Logical clock
Also known as: Lamport clock, vector clock
German: Logische Uhr
In distributed systems, a logical clock is a counter-based mechanism that assigns numbers to events so that their causal order can be determined without synchronized physical clocks; Lamport clocks and vector clocks are common forms.
- System integration
In one sentence
A logical clock numbers events so that their causal order can be determined without relying on synchronized physical clocks.
Example
Each edge node attaches a Lamport timestamp to its events, so the central system can order “recipe changed” before “batch started” even though the node clocks differ.
How it applies
- Engineering: Logical clocks help order events and detect concurrent updates in replicated data and event streams, without depending on clock accuracy. Vector clocks can also detect that two events are concurrent, which Lamport clocks cannot.
- Limits: Logical clocks say nothing about real time. For durations, response times or correlating with physical measurements, synchronized physical clocks are still needed.
- Documentation: Where event logs contain both logical sequence numbers and wall-clock timestamps, documentation should explain which one defines the order and which one is only informative.
Logical clock vs. physical clock
A physical clock, such as a device clock synchronized through a Global time base, measures real time. A logical clock only captures the order of events. In industrial systems both are often combined: physical timestamps for analysis, logical counters for ordering and duplicate detection.