delegator

Analysis, Planning, and Routing of cryptograms, a part of the delegator architecture.

What

The delegator service is an evaluation engine, offered as a key component of the delegator architecture.

Some high level features available via config file without extending the runtime itself:

• Virtualhost-style routing
• jq-like JSON transformations, available before and after every step in execution (see json-adapter for more)
• Interoperability with existing JSON APIs as steps during evaluation
• Experiment with novel service compositions without redeployment

Why

The delegator is currently offered in one of two variants, both as a standalone edge layer, as well as an in-progress realization of a broader ecosystem.

How

For exploratory integrations, it should be sufficient to launch the delegator pointing at a config file.

The configuration files make use of a concept called "cryptogram", as specified in .../cryptogram.rs, where Language is a jq-inspired transformation language from json-adapter.

An example config is as follows:

example.conf

[events.user_action]  # Stub
queue_url = "noop"

[http]
host = "0.0.0.0"
port = 8080
cors = []

[http.client]
user-agent = "delegator/0.1.0"
default-timeout = "30s"

[services.second] #  #  #  #  #  # Define a service, "second"...
protocol = "rest"
scheme = "http"
authority = "localhost:8080"  #  # Reachable at localhost:8080...

[services.second.methods.world]  # ... with a method "world".
path = "/world"
method = "POST"

[virtualhosts]

[virtualhosts.first]    # Define a virtualhost "first",
hostname = "localhost"  # ... listening on localhost,

[virtualhosts.first.routes."/hello"]  # ... exposing /hello,
                        # running the following program:
cryptogram = """
  {
    "steps": [
      {"payload": "Hello"},
      {"service": "second", "method": "world"}
    ]
  }
  """

[virtualhosts.second]   # Define a virtualhost "second",
hostname = "localhost"  # ... also listening on localhost

[virtualhosts.second.routes."/world"]  # exposing the method we described earlier
                        # running the following program:
cryptogram = """
  {
    "steps": [
      {"preflight": "[., const(\\"World!\\")] | join(\\", \\")"}
    ]
  }
  """

When run...

[nix-shell:~/Projects/delegator]$ cargo run ./helloworld.conf
    Finished dev [unoptimized + debuginfo] target(s) in 0.08s
     Running `target/debug/delegator ./helloworld.conf`
Preparing to bind to 0.0.0.0:8080
[2024-05-05T03:36:13Z INFO  actix_server::builder] starting 14 workers
[2024-05-05T03:36:13Z INFO  actix_server::server] Actix runtime found; starting in Actix runtime

... and then hit with cURL:

$ curl localhost:8080/hello --json '{}'
"Hello, World!"

... you'll see (in the access logs,) /world accessed by delegator/0.1.0, as well as /hello accessed by cURL:

[2024-05-05T03:36:15Z INFO  accesslog] 127.0.0.1 "POST /world HTTP/1.1" 200 15 "-" "delegator/0.1.0" 0.027343
[2024-05-05T03:36:15Z INFO  accesslog] 127.0.0.1 "POST /hello HTTP/1.1" 200 15 "-" "curl/8.4.0" 0.067537

... since /hello issued a call to {"service":"second", "method":"world"}, served by localhost:8080/world.

$ cargo run -- ./config/development.conf