websocket communication with Fedora apps.
See-also: fedmsg-gateway SOP
Messaging SIG, Fedora Infrastructure Team
#fedora-apps, #fedora-admin, #fedora-noc
busgateway01, proxy0*, app0*
Expose a websocket server for FI apps to use
WebSocket is a protocol (an extension of HTTP/1.1) by which client web browsers can establish full-duplex socket communications with a server --the "real-time web".
The websocket server itself is a fedmsg-hub daemon running on busgateway01. It is configured to enable its websocket server component in the presence of certain configuration values.
haproxy mediates connections to the fedmsg-hub websocket server daemon. An stunnel daemon provides SSL support.
The connection flow is much the same as in the fedmsg-gateway SOP, but is somewhat more complicated.
"Normal" HTTP requests to our app servers traverse the following chain:
Client -> apache(proxy01) -> haproxy(proxy01) -> apache(app01)
The flow for a websocket requests looks something like this:
Client -> stunnel(proxy01) -> haproxy(proxy01) -> fedmsg-hub(busgateway01)
stunnel is listening on a public port, negotiates the SSL connection, and redirects the connection to haproxy who in turn hands it off to the fedmsg-hub websocket server listening on busgateway01.
At the time of this writing, haproxy does not actually load balance zeromq session requests across multiple busgateway0* machines, but there is nothing stopping us from adding them. New hosts can be added in ansible and pressed from busgateway01's template. Add them to the fedmsg-websockets listen in haproxy's config and it should Just Work.
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