Adaptive Last-Modified Rounding for HTTP Resource Validation
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Solution Overview
Problem
The HTTP Last-Modified header's maximum granularity of whole seconds leads to inaccurate validation responses when a resource is updated multiple times within the same second, causing clients to miss subsequent updates.
Innovation Solution
A computing device determines whether to round up or down the update time of a resource based on the timing of validation requests relative to a defined window, ensuring accurate validation and currency of resources by adjusting the timestamp accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the server uses the Last-Modified header with whole second granularity to indicate resource update time, then the header format is simple and compatible with HTTP specifications, but the server cannot accurately respond to validation requests when multiple updates occur within the same second, causing clients to miss updates
Solution Approach 1:
The patent applies dynamics by making the rounding behavior adaptive rather than fixed. The server dynamically adjusts whether to round up or round down the update time based on the comparison between the validation request timestamp and the actual update time. This dynamic adjustment resolves the contradiction by maintaining simple whole-second granularity while achieving accurate update validation through context-dependent rounding decisions.
Solution Approach 2:
The patent changes the parameter of timestamp representation from a fixed rounding rule to a conditional rounding rule. By introducing a comparison parameter (whether validation request time is before or after the update), the system transforms the static Last-Modified header into a dynamic validation mechanism that accurately reflects resource update status without requiring sub-second precision in the header format.
2Productivity
If the server rounds down the update time to the whole second, then clients may receive updates more frequently, but clients may receive false positives indicating they have up-to-date copies when they actually do not
Solution Approach 1:
The patent implements feedback by using the validation request timestamp as a reference point to determine rounding direction. The server compares the client's validation request time with the actual update time and adjusts the rounding behavior accordingly. This feedback mechanism ensures that rounding down only occurs when it accurately reflects the update status, preventing false positives while maintaining appropriate update delivery frequency.
Solution Approach 2:
The rounding behavior is made dynamic based on the temporal relationship between validation requests and updates. When the validation request occurs before the update within the same second, the server rounds down; when it occurs after, the server rounds up. This dynamic approach balances update delivery frequency with validation accuracy, resolving the contradiction between productivity and reliability.
3Reliability
If the server rounds up the update time to the whole second, then clients may receive fewer false positives about having up-to-date copies, but clients may miss updates that occur after their cached copy's timestamp
Solution Approach 1:
The patent uses feedback from the validation request timing to control rounding behavior. When validation requests occur frequently within the same second as updates, the server rounds up to prevent false positives. When validation requests occur less frequently, the server rounds down to prevent update loss. This feedback-driven approach balances reliability with information completeness.
Solution Approach 2:
The system dynamically switches between rounding up and rounding down based on the temporal context of validation requests. This dynamic behavior ensures that rounding up is applied only when necessary to prevent false positives, while rounding down is applied when it prevents update loss, thereby resolving the contradiction between validation accuracy and update information retention.
4Measurement precision
If the server provides exact sub-second update timestamps, then the update time precision is high, but the Last-Modified header cannot accommodate sub-seconds according to HTTP specifications
Solution Approach 1:
The patent resolves this contradiction by moving the precision information from the vertical dimension (header format) to the horizontal dimension (validation request timing). Instead of storing sub-second precision in the Last-Modified header, the system uses the temporal relationship between validation requests and updates to convey precise update timing information, maintaining header compatibility while achieving precision through a different dimensional approach.
Solution Approach 2:
The validation request timestamp serves as an intermediary that bridges the gap between the coarse-grained Last-Modified header and the fine-grained actual update time. By comparing this intermediary timestamp with the update time, the server can determine appropriate rounding behavior, effectively translating precise update information into the constrained header format without losing validation accuracy.
Data Source
AI summary
Methods, systems, computer-readable media, and apparatuses are described for sending different update times corresponding to a same version of a resource. A computing device may provide a version of a resource in response to requests from a plurality of different devices, and may indicate different update times for the version of the resource. The different update times may be based on times associated with the requests from the plurality of different devices.