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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
Provides the classes for the Vespa config proxy.
<p>The {@link com.yahoo.vespa.config.proxy.ProxyServer ProxyServer}
contains the main method that instantiates a new ProxyServer that
listens for incoming config requests from clients at a given
port. The ProxyServer handles communication with the remote server,
and keeps a cache of {@link com.yahoo.vespa.config.RawConfig RawConfig}
objects.
</p>
<p>This package is very slim, due to extensive reuse of low-level code from
the config client library.
</p>
<h2>Why Vespa needs a config proxy</h2>
<p>It is possible for a client to subscribe
to config from the config server directly. However, if all Vespa
services applied this philosophy, it would cause a tremendous load
on the server that would need to handle a very large number of
requests from individual clients. Even more importantly, it would
inflict a huge load on the network if all config requests were
sent to the remote server.
</p>
<p>
Typically, one config proxy is running on each host in a Vespa
installation, so each subscriber on that host sends requests to
the proxy and never to the remote server. The proxy is responsible
for keeping that config up-to-date on behalf of all clients that
subscribe to it. This means that multiple subscribers to the same
config (and using the same config id) maps to only one request
from the proxy to the external server.
</p>
<p>Another advantage with a local config proxy on each node is
that subscribers become less vulnerable to network
failures. Should the network or the remote server go down for a
short period, only the proxy will notice, hence removing overhead from
the subscribers.
</p>
*/
@com.yahoo.api.annotations.PackageMarker
package com.yahoo.vespa.config.proxy;
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