BEGIN:VCALENDAR VERSION:2.0 PRODID:-//pretalx//talks.staging.osgeo.org//foss4g-europe-2025//speaker//3L 7777 BEGIN:VTIMEZONE TZID:CET BEGIN:STANDARD DTSTART:20001029T040000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET TZOFFSETFROM:+0200 TZOFFSETTO:+0100 END:STANDARD BEGIN:DAYLIGHT DTSTART:20000326T030000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST TZOFFSETFROM:+0100 TZOFFSETTO:+0200 END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:pretalx-foss4g-europe-2025-NH7Y8G@talks.staging.osgeo.org DTSTART;TZID=CET:20250718T110000 DTEND;TZID=CET:20250718T113000 DESCRIPTION:Real-time GIS has become an essential tool in various domains\, including Volunteered Geographic Information (VGI) and disaster managemen t. One of critical topics in real-time GIS is concurrency control (Sun and Li 2016). In the geospatial domain\, concurrency has traditionally been c ontrolled using optimistic or pessimistic models (i.e. versioning and lock ing\, respectively). In the domain of distributed databases\, a standard c onsistency model\, called strong consistency\, ensures that a set of distr ibuted databases behave as if they were a single database. However\, enfor cing strong consistency can introduce bottlenecks and lags\, and requires significant hardware resources and time to implement. \n\nTo address these drawbacks\, a more relaxed approach called strong eventual consistency (S EC) (Gomes et al. 2017) has been developed in the domain of real-time text co-editing. Unlike strong consistency\, SEC lets each site edit its local copy of the data without any restrictions and replicate all the updates t o all other sites\, which\, upon reception\, apply them on their local dat a. Temporary local inconsistencies are allowed between the participating s ites\, but it is guaranteed that\, once all sites have received the same s et of updates\, they will be in the same state (i.e.\, they will converge) .\n\nIt has recently been shown that SEC model i.e. its instantiation\, CR DT (Commutative Replicated Data Type) technology (Shapiro et al. 2011) can also be used for the task of geospatial co-editing. Within the research ( Matijević et al. 2024)\, an experimental real-time geospatial co-editor ( source code referenced in the original paper) has been developed and teste d. The implementation uses OpenLayers (OL) on the graphical user interface (GUI) and a small\, unoptimized but complete and correct Javascript CRDT library called Reference CRDTs (Gentle 2023). The research showed that\, w hen applied to the co-editing of geospatial geometry in its native form\, standard CRDT conflict resolution mechanics exhibit some issues. As an att empt to address these issues\, the authors developed an advanced operation generation technique named “tentative operations”. This technique all ows for the operations to be generated over the most recent session-wide s tate of the data\, which in effect highly reduces concurrency and provides a “geometry aware” conflict resolution. The tests conducted using the developed system showed that in low-latency network conditions\, the nega tive effects of standard CRDT conflict resolution mechanics do get minimiz ed even under increased loads (many concurrent sites co-editing a low vert ex count geometry).\n\nReal-time co-editors generally aim to provide good user experience of the system\, with correct handling of conflicts being o ne of its important aspects. However\, besides correct handling of conflic ts\, the system also has to be responsive. The responsiveness of real-time co-editors depends on the efficiency of the underlying business logic but also on the efficiency of the GUI itself. Especially in the case of geosp atial data manipulation\, both the GUI and the business logic will be addi tionally stressed by increasing the vertex count of geometries being co-ed ited. Since within the original research the tests were performed using po lygons low vertex count (several hundreds)\, it remained unknown how would a CRDT based geospatial co-editor behave when much larger geometries (e.g . hundreds of thousands of vertices) are co-edited.\n\nWithin this researc h we therefore investigate the impact that the increase of vertex count ha s on the overall performance of the system\, which in turn can hinder resp onsiveness. We reused the existing implementation from (Matijević et al. 2024) and only introduced minor modifications to achieve the ability to ti me the execution of its key mechanisms. Instead of focusing on the perform ance of CRDT mechanisms only\, we observed the behaviour of the complete s ystem. We first analysed the overall composition of the system and divided it into several distinct parts. Then\, during load testing we observed ho w the performance of each of those parts changes when handling geometries with increasing vertex counts. To stress the system\, we created three pol ygons with 100K\, 200K and 300K vertexes and conducted real co-editing ses sions over those polygons. The upper limit of 300K was selected based on p reliminary testing which showed that already at this vertex count OL start s to lose responsiveness in editing mode. The sessions were conducted usin g several identical instances of some recent\, mainstream hardware and the latest Google Chrome browser.\n\nAs expected\, the results of the experim ent show that the overall performance of the system does suffer from the i ncreased vertex count of the geometry being co-edited. In the setting as i mplemented within the research (Matijević et al. 2024) the part most affe cted by the increased vertex count turned out to be the redrawing on GUI u pon integration of remote updates while the client is in editing mode. Thi s is because the implementation uses a simple redraw method where the comp lete geometry is replaced by its new version.\n\nThe results from this res earch show that geometries with high vertex count can efficiently be co-ed ited in real-time. However\, there exists a limit where the increased vert ex count will start to render the system irresponsive\, depending on the c apabilities of the hardware that the clients are running on.\n\nThe result s from this research are to be observed in the setting which includes both CRDT and OL written in Javascript\, with CRDT implementation including on ly some simple optimizations and with no tighter CRDT-OL coupling other th an what OL offers off-the-shelf. It can therefore be expected that a deepe r integration of CRDT mechanisms with OL could make some of the critical p arts of the implementation faster. Also\, there exist several mature\, pro duction ready open-source CRDT frameworks which include many optimizations and can outperform the Reference CRDTs by orders of magnitude. DTSTAMP:20260527T015044Z LOCATION:PA01 (Quarticle) SUMMARY:Real Time Co-editing of High Vertex Count Geometries Using OpenLaye rs and CRDTs - a Performance Analysis - Hrvoje Matijević URL:https://talks.staging.osgeo.org/foss4g-europe-2025/talk/NH7Y8G/ END:VEVENT END:VCALENDAR