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GENI Instrumentation and Measurement System - Schema

GENI Instrumentation and Measurement System - Schema. Martin Swany. Schema. Generally: model of objects and their relationships We should talk in terms of the general “schema” in this sense Renderings later XML schema SQL schema IPFIX JSON. I&M Schema Requirements.

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GENI Instrumentation and Measurement System - Schema

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  1. GENI Instrumentation and Measurement System -Schema Martin Swany

  2. Schema • Generally: model of objects and their relationships • We should talk in terms of the general “schema” in this sense • Renderings later • XML schema • SQL schema • IPFIX • JSON

  3. I&M Schema Requirements • Consistent basic representation of measurement and instrumentation data inside and outside of a slice • Flexibility of encoding and transport • timestamp and value or values • Expressive metadata • Easily extensible • Reusable components and models • Reasonable relationship to RSpec

  4. perfSONAR Model • perfSONAR is an internationally-adopted framework for instrumentation and measurement • Based on schemata and protocols defined in the *Grid Forum over the last 10 years • Recognized by the NSF as a key technology; recent NSF-funded workshop • Again, consider the model in the abstract rather than the XML encoding or RNC files

  5. perfSONAR Schema • Key Goals: Extensibility, Normalization, Readability • Break representation of performance measurements down into basic elements • Data and Metadata • Measurement Data • A set of of measurement events that have some value or values at a particular time • Measurement Metadata • The details about the set of measurement data

  6. Schema Normalization • Can simplify the database representation for many types of measurement data • While optimizations are possible, many measurement types can be viewed as one value measured over time • Assists Combination/Concatenation of metrics • Creating derived metrics • Normalization helps with inferring relationships between types of metrics

  7. Schema Basic Elements - Metadata • Subject (Noun) • The measured/tested entity • EventType (Verb) • What type of measurement or event occurred, or instrumented parameter was read • Characteristic, tool output, or generic event • Parameters (Adjectives and Adverbs) • How, or under what conditions, did this event occur?

  8. Schema Basic Elements - Data • Some sort of value - Datum • Existence of an event might point to the case where there no additional value • As in “Link up/down” or threshold events • Time • Is extensible since various representations are appropriate in different cases • E.g. UNIX timestamp vs NTP time

  9. Metadata Data A Message Message Message

  10. Metadata Data An Object Store Store

  11. A Data is Linked to a Metadata Metadata <id>someId</id> Data <metadataIdRef> someId </metadataIdRef>

  12. A Metadata may be linked to another Metadata <id>someId</id> Metadata <id>someOtherId</id> <metadataIdRef> someId </metadataIdRef>

  13. Schema Namespaces • Observation: all measurements have some sort of Data and Time • All measurements can be described by the Metadata identifying who, what and how • The specific structures of the Data and Metadata elements depend on the measurement • Approach: Consistently use Data and Metadata elements and vary the namespaces of the specific elements

  14. Schema Namespaces - 2 • We encode the measurement/event type in the namespace • And as a standalone element • Some components of the system can pass Data and Metadata elements through without understanding their specific structure • Allows and implementation to decide whether it supports a particular type of data or not • Allows validation based on extended (namespace-specific) schemata

  15. Schema Namespaces and Extensibility • One key to extensibility is the use of hierarchy with delegation • Similar to OIDs in the IETF management world • The OGF NM-WG defined a hierarchy of network characteristics • Good starting point • However, not all tools are cleanly mapped onto the Characteristic space • Often a matter of some debate

  16. Schema Namespaces and Extensibility • Organization-rooted tools namespace addresses this • Some top-level tools • ping, traceroute • Easy to add new tools in organization-specific namespaces • Performance Event Repository • Add a schema and get a URI • Add Java classes

  17. Linking Metadata • Metadata can be linked in two ways • Merge chaining allows for elements to be reused and a complete metadata can be built • Operation chaining requests or describes operations on data sets • Representation of data provenance A A A B B(A) B B

  18. Resources, Subjects, Topology • perfSONAR has a topology schema called UNIS – Unified Network Information Schema • Related to the control frameworks’ Resource Specification • Measurement and Instrumentation must be related to the resources themselves

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