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Table of Contents
Reverse proxy for Synapse with workers
Changing nginx's configuration from a reverse proxy for a normal, monolithi Synapse to one for a Synapse that uses workers, quite a lot has to be changed.
As mentioned in Synapse with workers, we're changing from network sockets to UNIX sockets.
Because we're going to have to forward a lot of specific requests to all kinds of workers, we'll split the configuration into a few bits:
** all proxy_forward settings
** all location definitions
** maps that define variables
** upstreams that point to the correct socket(s) with the correct settings
** settings for private access
** connection optimizations
Some of these go into /etc/nginx/conf.d because they are part of the
configuration of nginx itself, others go into /etc/nginx/snippets because we
need to include them several times in different places.
Maps
A map sets a variable based on, usually, another variable. One case we use is determining the type of sync a client is doing. A normal sync, simply updating an existing session, is a rather lightweight operation.
An initial sync, meaning a full sync because the session is brand new, is not so lightweight.
A normal sync can be recognised by the since bit in the request: it tells
the server when its last sync was. If there is no since, we're dealing with
an initial sync.
Initial syncs are forwarded to the initial_sync workers, the normal syncs to
normal_sync.
We decide to which type of worker to forward the sync request to by looking at
the presence or absence of since: if it's there, it's a normal sync and we
set the variable $sync to normal_sync. If it's not there, we set $sync to
initial_sync.
The last bit is to foward the request to the upstream $sync. This is what
that map looks like:
map $arg_since $sync {
default normal_sync;
'' initial_sync;
}
We filter the argument since by using $arg_since, see the index of
variables in nginx for more
variables we can use.