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Review fedmsg-relay SOP

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Remove the link to topology diagram, it's not working anymore. And I
didn't find it in the documentation.

Signed-off-by: Michal Konečný <mkonecny@redhat.com>
This commit is contained in:
Michal Konečný 2021-08-19 14:09:06 +02:00
parent 3c43f7638d
commit d5b724b2d8
2 changed files with 12 additions and 14 deletions
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24
modules/sysadmin_guide/pages/fedmsg-relay.adoc
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@ -15,44 +15,42 @@ Purpose::
== Description
fedmsg-relay is running on app01, which is a bad choice. We should look
to move it to a more isolated place in the future. busgateway01 would be
_fedmsg-relay_ is running on _app01_, which is a bad choice. We should look
to move it to a more isolated place in the future. _busgateway01_ would be
a better choice.
"Ephemeral" scripts like `pkgdb2branch.py`, the post-receive git hook on
pkgs01, and anywhere fedmsg-logger is used all depend on fedmsg-relay.
_pkgs01_, and anywhere _fedmsg-logger_ is used all depend on _fedmsg-relay_.
Instead of emitting messages "directly" to the rest of the bus, they use
fedmsg-relay as an intermediary.
Check that fedmsg-relay is running by looking for it in the process
Check that _fedmsg-relay_ is running by looking for it in the process
list. You can restart it in the standard way with
`sudo service fedmsg-relay restart`. Check for its logs in
`/var/log/fedmsg/fedmsg-relay.log`
Ephemeral scripts know where the fedmsg-relay is by looking for the
Ephemeral scripts know where the _fedmsg-relay_ is by looking for the
relay_inbound and relay_outbound values in the global fedmsg config.
== But What is it Doing? And Why?
The fedmsg bus is designed to be "passive" in its normal operation. A
mod_wsgi process under httpd sets up its fedmsg publisher socket to
The _fedmsg_ bus is designed to be "passive" in its normal operation. A
_mod_wsgi_ process under _httpd_ sets up its _fedmsg_ publisher socket to
passively emit messages on a certain port. When some other service wants
to receive these messages, it is up to that service to know where
mod_wsgi is emitting and to actively connect there. In this way,
_mod_wsgi_ is emitting and to actively connect there. In this way,
emitting is passive and listening is active.
We get a problem when we have a one-off or "ephemeral" script that is
not a long-running process -- a script like pkgdb2branch which is run
not a long-running process -- a script like _pkgdb2branch_ which is run
when a user runs it and which ends shortly after. Listeners who want
these scripts messages will find that they are usually not available
when they try to connect.
To solve this problem, we introduced the "fedmsg-relay" daemon which is
To solve this problem, we introduced the "_fedmsg-relay_" daemon which is
a kind of "passive"-to-"passive" adaptor. It binds to an outbound port
on one end where it will publish messages (like normal) but it also
binds to an another port where it listens passively for inbound
messages. Ephemeral scripts then actively connect to the passive inbound
port of the fedmsg-relay to have their payloads echoed on the
port of the _fedmsg-relay_ to have their payloads echoed on the
bus-proper.
See http://fedmsg.readthedocs.org/en/latest/topology/ for a diagram.