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Loki - Server

Serve you Tips and tricks to fluidify your (public) transit !

Description

Reads a ntfs dataset and then process protobuf journey requests (the format is specified by the navitia-proto repo) send to a zmq socket, call the loki engine, and returns the protobuf response on the zmq socket.

How to compile

Install libzmq (needed for the zmq crate, cf https://crates.io/crates/zmq/):

apt install libzmq3-dev

Be sure to fetch the navitia-proto git submodule.

git submodule init    # a first time, to fetch the navitia-proto repo
git submodule update  # each time the navitia-proto repo is updated
cargo build --release

How to use

Loki-server can be used to answer the "public transit" part of distributed journey request. The setup is as follow :

  • a jormun server will receive the distributed journey request, and create several subrequest to be handled by backends, before serving the response
  • a loki-server backend will answer all "pt_journey" subrequests
  • a kraken backend will answer all other subrequests

You should have a ntfs dataset in /path/to/ntfs which has been binarized to /path/to/data.nav.lz4 (you can use eitry for generating a data.nav.lz4 from a ntfs dataset). You need to setup :

  • a jormun server from this branch which should be configured with
{"key": "mycoverage", "zmq_socket": "ipc:///tmp/kraken", "pt_zmq_socket" : "ipc:///tmp/loki"}
  • a kraken configured with
[GENERAL]
instance_name = "mycoverage"
database = /path/to/data.nav.lz4
zmq_socket = ipc:///tmp/kraken
  • a loki server launched with 
    cargo run --release -- launch --input_data_path /path/to/ntfs  --input_data_type ntfs --basic_requests_socket ipc:///tmp/loki

Then you can send http requests to the jormun server !

Architecture

Protobuf

This crate uses prost to handle (de)serialization of protobuf. The protobuf schema is specified in navitia-proto. This means that Rust code is generated from .proto files at compile time, by prost-build in the build script build.rs. To see where the rust code is generated, run

cargo build --release -vv

And you should see a line like the following in the output :

[server 0.1.0] Writing protobuf code in /home/pascal/loki/target/release/build/server-52f917f3d3486970/out/pbnavitia.rs

See this page for more information on build scripts.