Built-in services and service classes

The syndicate-server program includes built-in knowledge about a handful of useful services, including a means of loading external programs and integrating them into the running system.

• Every server program starts a gatekeeper service, which is able to manage conversion between live references and so-called “sturdy refs”, long-lived capabilities for access to resources managed by the server.

• A simple logging actor copies log messages from the system dataspace to the server’s standard error file descriptor.

• Any number of TCP/IP, WebSocket, and Unix socket transports may be configured to allow external access to the gatekeeper and its registered services. (These can also be started from the syndicate-server command-line with -p and -s options.)

• Any number of configuration watchers may be created to monitor directories for changes to files written using the server scripting language. (These can also be started from the syndicate-server command-line with -c options.)

• Finally, external programs can be started, either as long-lived “daemon” services or as one-off scripts.

Resources available at startup

The syndicate-server program uses the Rust tracing crate, which means different levels of internal logging verbosity are available via the RUST_LOG environment variable. See here for more on RUST_LOG.

If tracing of Syndicated Actor Model actions is enabled with the -t flag, it is configured prior to the start of the main server actor.

As the main actor starts up, it

• creates a fresh dataspace, known as the $config dataspace, intended to contain top-level/global configuration for the server instance;

• creates a fresh dataspace, known as $log, for assertions and messages related to service logging within the server instance;

• creates the $gatekeeper actor implementing the gatekeeper service, attaching it to the $config dataspace;

• exposes $config, $log and $gatekeeper as the variables available to configuration scripts loaded by config-watchers started with the -c flag (N.B. the $config dataspace is thus the default target for assertions in config files);

• creates service factories monitoring various service assertions in the $config dataspace;

• processes -p command-line options, each of which creates a TCP/IP relay listener;

• processes -s command-line options, each of which creates a Unix socket relay listener;

• processes -c command-line options, each of which creates a config-watcher monitoring a file-system directory; and finally

• creates the logging actor, listening to certain events on the $log dataspace.

Once these tasks have been completed, it quiesces, leaving the rest of the operation of the system up to other actors (relay-listeners, configuration scripts, and other configured services).

Copyright © 2021–2023 Tony Garnock-Jones, CC BY 4.0