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Configuration proxy

Read application packages for an overview of the cloud config system. The config proxy runs on every Vespa node. It has a set of config sources, defined in VESPA_CONFIGSERVERS.

The config proxy will act as a proxy for config clients on the same machine, so that all clients can ask for config on localhost:19090. The config source that the config proxy uses is set in VESPA_CONFIGSERVERS and may consist of one or more config sources (usually config servers, but may be other config proxies).

The proxy has a memory cache that is used to serve configs if it is possible. In default mode, the proxy will have an outstanding request to the config server that will return when the config has changed (a new generation of config). This means that every time config changes on the config server, the proxy will get a response, update its cache and respond to all its clients with the changed config.

The config proxy has two modes:

Mode Description
default Gets config from server and stores in memory cache. The config proxy will always be started in default mode. Serves from cache if possible. Always uses a config source. If restarted, it will lose all configs that were cached in memory.
memorycache Serves config from memory cache only. Never uses a config source. A restart will lose all cached configs. Setting the mode to memorycache will make all applications on the node work as before (given that they have previously been running, and requested config), since the config proxy will serve config from cache and work without any connection to the config server. Applications on this node will not work if the config proxy stops, is restarted or crashes.

Interface with the config proxy using vespa-configproxy-cmd - run it without arguments to see usage. The tool displays heap usage for the proxy, displays the configs cached and flushes the cache. View the pending requests it has against the server(s). A pending request is the same as a subscription of server data, the requests are held open until the data changes on the server, through a vespa activate.

Detaching from config servers

$ vespa-configproxy-cmd -m setmode memorycache

Inspecting config

To inspect the configuration for a service, in this example a searchnode (proton) instance, do:

  1. Find the active config generation used by the service, using /state/v1/config - example for http://localhost:19110/state/v1/config, here the generation is 2: 
    {
    "config": {
        "generation": 2,
        "proton": {
            "generation": 2
        },
        "proton.documentdb.music": {
            "generation": 2
        }
    }
}
  2. Find the relevant config definition name, config id and config generation using vespa-configproxy-cmd - e.g.: 
    $ vespa-configproxy-cmd | grep proton

vespa.config.search.core.proton,music/search/cluster.music/0,2,MD5:40087d6195cedb1840721b55eb333735,XXHASH64:43829e79cea8e714
    vespa.config.search.core.proton is the config definition name for this particular config, music/search/cluster.music/0 is the config id used by the proton service instance on this node and 2 is the active config generation. This means, the service is using the correct config generation as it is matching the /state/v1/config response (a restart can be required for some config changes).
  3. Get the generated config using vespa-get-config - e.g.: 
    $ vespa-get-config -n vespa.config.search.core.proton -i music/search/cluster.music/0

basedir "/opt/vespa/var/db/vespa/search/cluster.music/n0"
rpcport 19106
httpport 19110
...