@danielmitterdorfer I just happened to see the issue thread, and ingest-user-agent was mentioned there. We actually did another rally benchmark with that ingest plugin as well and we found around 35% indexing performance hit with it; the weirdest part was that the "agent" source field value that we have is exactly the same across all of the 5mil docs, we thought it would be much faster but apparently not so much..
These are some of the few lines of the input docs fo reference,
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{"@timestamp":"2016-12-08T23:54:57.272+0000","clientip":"67.59.33.139","response":"200","request":"/Unless.OF?os_destination\u003dWARRANTIES/and.permissions\u0026xxx\u003dexpress\u0026yyy\u003dunder\u0026id\u003d345","bytes":"15651","referer":"/pages/editpage.action","agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7","uid":"7786045c-fe6d-48e6-b183-d5f7b12c215e","pagetime":"615"}
{"@timestamp":"2016-12-08T23:54:57.273+0000","clientip":"33.17.149.6","response":"200","request":"/BASIS.writing?os_destination\u003dan/BASIS.or\u0026xxx\u003dan\u0026yyy\u003dfor\u0026id\u003d193","bytes":"15651","referer":"/pages/editpage.action","agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7","uid":"76cbbc43-746c-43ac-95ea-c7563e00a299","pagetime":"304"}
{"@timestamp":"2016-12-08T23:54:57.273+0000","clientip":"44.24.40.67","response":"200","request":"/BASIS.OF?os_destination\u003dWITHOUT/distributed.License\u0026xxx\u003ddistributed\u0026yyy\u003din\u0026id\u003d207","bytes":"15651","referer":"/pages/editpage.action","agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7","uid":"3cfdf2ed-f309-40ad-9af4-7f965b7866c2","pagetime":"792"}
{"@timestamp":"2016-12-08T23:54:57.273+0000","clientip":"178.85.183.115","response":"200","request":"/language.AS?os_destination\u003dor/an.language\u0026xxx\u003dANY\u0026yyy\u003drequired\u0026id\u003d9","bytes":"15651","referer":"/pages/editpage.action","agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7","uid":"20a214e5-bf8f-4e97-8808-f48c8100b660","pagetime":"200"}
{"@timestamp":"2016-12-08T23:54:57.273+0000","clientip":"21.203.59.189","response":"200","request":"/implied.law?os_destination\u003dKIND/required.the\u0026xxx\u003dsoftware\u0026yyy\u003dUnless\u0026id\u003d185","bytes":"15651","referer":"/pages/editpage.action","agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7","uid":"c1d27c6c-efd7-40f4-9777-572847b34597","pagetime":"19"}