Using XMPP JSONPatch for synchronizing an OpenUI5 Model
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The document discusses synchronization challenges in distributed storage systems under the CAP theorem, proposing a solution that utilizes availability and eventual consistency. It highlights conflict-free replicated data types (CRDTs) and the use of XMPP for message distribution through the publish-subscribe paradigm. Additionally, it mentions various technologies including the Strophe library for XMPP in JavaScript, JSON Patch for describing differences in JSON objects, and the xxhash algorithm for duplication detection.
Using XMPP JSONPatch for synchronizing an OpenUI5 Model
- 2. The Problem ● I want to synchronize different datastores
- 3. CAP Theorem ● A distributed storage can only have 2 of the following three properties: – Consistency – a read will always respond with the most current data – Availability – a node will give a reasonable response within a reasonable amount of time – Partition tolerant – the system will still work when nodes are not reachable
- 4. Proposed solution ● The proposed solution is AP and eventual consitent ● This means: – All nodes are always available and can work without speaking to any other node – When back connected to the network all nodes will converge to have the same data
- 6. CRDT ● Conflict free replicated data type ● Data structures that don‘t produce conflicts when merged ● e.g. – State-based PN-Counter – State based grow-only set – last write wins element sets with vector clocks – ...
- 7. XMPP PubSub XEP-0060 ● Specification for distributing messages ● Publish-Subscribe paradigm https://xmpp.org/extensions/xep-0060.html <iq type='set' from='hamlet@denmark.lit/blogbot' to='pubsub.shakespeare.lit' id='publish1'> <pubsub xmlns='http://jabber.org/protocol/pubsub'> <publish node='princely_musings'> <item id='bnd81g37d61f49fgn581'> <entry xmlns='http://www.w3.org/2005/Atom'> <title>Soliloquy</title> <summary> To be, or not to be: that is the question: Whether 'tis nobler in the mind to suffer The slings and arrows of outrageous fortune, Or to take arms against a sea of troubles, And by opposing end them? </summary> <link rel='alternate' type='text/html' href='http://denmark.lit/2003/12/13/atom03'/> <id>tag:denmark.lit,2003:entry-32397</id> <published>2003-12-13T18:30:02Z</published> <updated>2003-12-13T18:30:02Z</updated> </entry> </item> </publish> </pubsub> </iq>
- 8. Strophe ● XMPP Web Socket Library ● JavaScript ● Verschiedene Authorisierungen ● Callbacks um auf XMPP Nachrichten zu antworten ● Logging
- 9. JSON Patch ● Specification for describing differences between to JSON objects ● Used for describing the addition to the set { "op": add", "path":"/inserts/62afb01a", "value": { "created":"2017-03-19T10:41:48.823Z", "title":"Hello World" } }
- 10. xxHash ● Non cryptographic fast hashing algorithm ● Can be used for duplication detection ● Advantage: – Data with same content won‘t duplicate in case of data entry of different offline nodes ● Disadvantage – Data without changing fields like timestamps or UUIDs can be reentered once deleted
- 11. OpenUI5 ● MVC JavaScript framework ● Basis for SAP Fiori ● Rich widget library ● Responsive ● Well integrated with server based on Models e.g. – JSON – OData
- 12. Demo
- 13. Questions?