{"action":"created","issue":{"url":"https://api.github.com/repos/crossbario/crossbar/issues/1445","repository_url":"https://api.github.com/repos/crossbario/crossbar","labels_url":"https://api.github.com/repos/crossbario/crossbar/issues/1445/labels{/name}","comments_url":"https://api.github.com/repos/crossbario/crossbar/issues/1445/comments","events_url":"https://api.github.com/repos/crossbario/crossbar/issues/1445/events","html_url":"https://github.com/crossbario/crossbar/issues/1445","id":385881251,"node_id":"MDU6SXNzdWUzODU4ODEyNTE=","number":1445,"title":"Channel redirect commands","user":{"login":"sjdv1982","id":8017841,"node_id":"MDQ6VXNlcjgwMTc4NDE=","avatar_url":"https://avatars1.githubusercontent.com/u/8017841?v=4","gravatar_id":"","url":"https://api.github.com/users/sjdv1982","html_url":"https://github.com/sjdv1982","followers_url":"https://api.github.com/users/sjdv1982/followers","following_url":"https://api.github.com/users/sjdv1982/following{/other_user}","gists_url":"https://api.github.com/users/sjdv1982/gists{/gist_id}","starred_url":"https://api.github.com/users/sjdv1982/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sjdv1982/subscriptions","organizations_url":"https://api.github.com/users/sjdv1982/orgs","repos_url":"https://api.github.com/users/sjdv1982/repos","events_url":"https://api.github.com/users/sjdv1982/events{/privacy}","received_events_url":"https://api.github.com/users/sjdv1982/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":4,"created_at":"2018-11-29T19:04:15Z","updated_at":"2018-11-29T20:19:33Z","closed_at":null,"author_association":"NONE","body":"I would like to suggest a feature, which I think will be useful for myself and others. I can code it myself, if the PR would be accepted (or even if not), but I would like to hear if you think it a good idea or not.\r\n\r\nI am mostly interested in Crossbar to coordinate a cluster of computing nodes. I want precise control over which node receives which job, so I don't want to use slurm/torque, nor do I want to use any kind of automatic load balancer (random, round-robin or otherwise). In any case, each job is a stream of requests, with large payloads per request.\r\n\r\nFor my case, Crossbar is ideal, because I can set up WAMP channels for each worker (input.workerX and output.workerX), and my own frontend, with input.frontend and output.frontend channels. All job streams would go to input.frontend (in the public realm) and the frontend would then decide dynamically where to send it.\r\nNow, I could already do this, but the frontend would have to re-encode each request and send it back to the router on the input.workerX channel, to be forwarded to the worker. With big payloads and multiple layers of frontends, this would be very bad for performance.\r\n\r\nWhat I would like to implement is a special kind of channel, the redirect channel. \r\nAny message sent over the  redirect channel will be interpreted by Crossbar.io as a redirect command. \r\nA redirect command must have the format `<command>, <source channel>, <target channel>, [target realm]`. \r\n`<command>` must be \"add\" or \"remove\". A redirect command causes all messages from `<source channel>` to be sent to `<target channel>` in the target realm. \r\n\r\n- Every realm may have one redirect channel, of which the name must be configured in config.json.\r\n- Only clients with {\"allow\": {\"redirect\": true}}  are allowed to send messages to the redirect channel.\r\n- Every realm may have a list of friend realms (empty by default) that are allowed to target the realm via redirect commands.\r\n\r\nAs far as I can see, the place to store redirect commands would be in the UriObservationMap class in crossbar/router/observation.py.\r\n\r\nFor this to work, the ordering guarantees of the WAMP protocol must be strong enough (I was not sure from reading the spec).\r\nIs the event handler of a client required to be synchronous and unbuffered? In other words, if a client responds to a event X with an unsubscribe, is it guaranteed that it will never receive event X+1 (from the same channel)?\r\nAre subscribe and unsubscribe guaranteed to be ordered? If in an event handler, a client subscribes to A and unsubscribes to B, will it at every point in time be subscribed to A XOR B? \r\n"},"comment":{"url":"https://api.github.com/repos/crossbario/crossbar/issues/comments/442979015","html_url":"https://github.com/crossbario/crossbar/issues/1445#issuecomment-442979015","issue_url":"https://api.github.com/repos/crossbario/crossbar/issues/1445","id":442979015,"node_id":"MDEyOklzc3VlQ29tbWVudDQ0Mjk3OTAxNQ==","user":{"login":"meejah","id":145599,"node_id":"MDQ6VXNlcjE0NTU5OQ==","avatar_url":"https://avatars3.githubusercontent.com/u/145599?v=4","gravatar_id":"","url":"https://api.github.com/users/meejah","html_url":"https://github.com/meejah","followers_url":"https://api.github.com/users/meejah/followers","following_url":"https://api.github.com/users/meejah/following{/other_user}","gists_url":"https://api.github.com/users/meejah/gists{/gist_id}","starred_url":"https://api.github.com/users/meejah/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/meejah/subscriptions","organizations_url":"https://api.github.com/users/meejah/orgs","repos_url":"https://api.github.com/users/meejah/repos","events_url":"https://api.github.com/users/meejah/events{/privacy}","received_events_url":"https://api.github.com/users/meejah/received_events","type":"User","site_admin":false},"created_at":"2018-11-29T20:19:33Z","updated_at":"2018-11-29T20:19:33Z","author_association":"MEMBER","body":"So essentially you want to publish to topic \"redirect\" always but be able to \"re-target\" where which topic that publish is \"really\" sent out on..?\r\n\r\nIf so, one approach w/o modifying crossbar could be to run a component \"in/alongside\" the router which simply does that: re-publishes the event to whatever the new topic is. If this component is written in Twisted, it can run in the same process as the router-process (and hence, even though you're technically re-publishing something large, it should be very fast as it's all in-memory and not round-tripping over the network to some other component)."}}
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