reverter: download objects history in parallel while restoring/undeleting

[naoliv]

When reverting a larger changeset (with a considerable number of objects) we can see that the reverter plugin takes some time to download the objects history, one by one.
Could this be improved by downloading them in parallel? (4, by default, maybe).

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2015-03-30 01:30:55
Last Changed Author: stoecker
Revision: 8159
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Relative URL: ^/trunk
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2015-03-29 14:37:50 +0200 (Sun, 29 Mar 2015)
Last Changed Rev: 8159

Identification: JOSM/1.5 (8159 pt_BR) Linux Debian GNU/Linux 8.0 (jessie)
Memory Usage: 750 MB / 4029 MB (124 MB allocated, but free)
Java version: 1.7.0_75, Oracle Corporation, OpenJDK 64-Bit Server VM
Java package: openjdk-7-jre:amd64-7u75-2.5.4-3
VM arguments: [-Dawt.useSystemAAFontSettings=on]
Dataset consistency test: No problems found

Plugins:
- AddrInterpolation (30892)
- Create_grid_of_ways (30892)
- FastDraw (30892)
- FixAddresses (30892)
- ImageryCache (30892)
- OpeningHoursEditor (30962)
- PicLayer (30962)
- SimplifyArea (30962)
- buildings_tools (30955)
- download_along (30892)
- editgpx (30892)
- geotools (31068)
- graphview (30892)
- jts (31002)
- measurement (30892)
- merge-overlap (30988)
- opendata (31050)
- pdfimport (30892)
- poly (31056)
- reverter (30990)
- tagging-preset-tester (30892)
- todo (29154)
- turnrestrictions (31034)
- undelete (30892)
- utilsplugin2 (31040)

[simon04]

A more performant way would be an enhancement of the API. I created a ticket: ​https://github.com/openstreetmap/openstreetmap-website/issues/1067

[mmd]

This has been implemented in cgimap in the meantime, Rails port is still open (but not used anyway for this API call): ​https://github.com/openstreetmap/openstreetmap-website/pull/1189

[GerdP]

I think the performance is very good with current binaries.

[GerdP]

History data is downloaded with multifetch since [o35078]. Download is not done with parallel tasks but is very quick since then.