{"action":"closed","issue":{"url":"https://api.github.com/repos/Netflix/Hystrix/issues/955","labels_url":"https://api.github.com/repos/Netflix/Hystrix/issues/955/labels{/name}","comments_url":"https://api.github.com/repos/Netflix/Hystrix/issues/955/comments","events_url":"https://api.github.com/repos/Netflix/Hystrix/issues/955/events","html_url":"https://github.com/Netflix/Hystrix/issues/955","id":112519581,"number":955,"title":"HystrixCollapser completes without emitting","user":{"login":"amitcse","id":431013,"avatar_url":"https://avatars.githubusercontent.com/u/431013?v=3","gravatar_id":"","url":"https://api.github.com/users/amitcse","html_url":"https://github.com/amitcse","followers_url":"https://api.github.com/users/amitcse/followers","following_url":"https://api.github.com/users/amitcse/following{/other_user}","gists_url":"https://api.github.com/users/amitcse/gists{/gist_id}","starred_url":"https://api.github.com/users/amitcse/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/amitcse/subscriptions","organizations_url":"https://api.github.com/users/amitcse/orgs","repos_url":"https://api.github.com/users/amitcse/repos","events_url":"https://api.github.com/users/amitcse/events{/privacy}","received_events_url":"https://api.github.com/users/amitcse/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2015-10-21T06:12:12Z","updated_at":"2015-10-21T06:14:02Z","closed_at":"2015-10-21T06:14:02Z","body":"Hi, I am facing a weird issue wherein the observable returned by `HystrixCollapser` completes without emitting any item. Since I am using `HystrixCollapser.toObservable()` inside to do composition using RxJava operator, this is leading to items being missed from the data flow. \r\nOn debugging I have found that the `HystrixCollapser` do call the `HystrixCommand.run()` and `mapResponsetoRequests` function is also called. \r\nI am unable to debug this more because this behaviour is completely random. \r\n\r\nFor reference, my rx observable composition is something like this,\r\n```\r\nObservable.from(id1, id2, id3, ....)\r\n.flatMap(id -> collapser1(id))\r\n.flatMap(collapser1Result -> {\r\n    collapser2Observable = collapser2(collapser1Result);\r\n    collapser3Observable = collapser3(collapser1Result);\r\n    collapser4Observable = collapser4(collapser1Result);\r\n\r\n    return Observable.zip(collapser2Observable, collapser3Observable, collapser4Observable, \r\n        (collapser2Res, collapser3Res, collapser4Res) \r\n                    -> makeFinalResult(collapser2Res, collapser3Res, collapser4Res));\r\n})\r\n.map(finalResult -> doSomeTransformations(finalResult))\r\n.toList().toBlocking().single();\r\n```\r\nSince any of collapser2/3/4 completes without emitting, this lead to zip being called and corresponding related result goes missing from the final list.\r\n"}}