Launcher Reference

The launcher is a lightweight artifact (~122K) that installs and configures bloop. The goal of the launcher is to relieve clients of the burden of installing and managing the lifetime of background build servers.

The launcher implements the Build Server Discovery protocol which allows clients to establish a bsp connection and communicate with the server via stdin and stdout.

`launcher`

Usage

Synopsis: launcher [JVM_OPTS...] [FLAGS...] BLOOP_VERSION

BLOOP_VERSION must be a bloop version >= 1.2.0. This version is only used in case an installation is tried.

There is no guarantee that the server provided to the client will be of this version.
JVM_OPTS must be valid JVM arguments prefixed with -J.

Flags

--skip-bsp-connection (type: bool): Do not attempt a bsp connection, but exit as soon as bloop has been installed and a server is running in the background.

Description

The high-level logic steps of the launcher can be summarized as follows:

If bloop is not detected in the $PATH or $HOME/.bloop/, install it.
- If the universal installation (that requires curl and python) fails, then we attempt to resolve bloop and launch an embedded server with a concrete bsp command. This operation is only atempted if and only if --skip-bsp-connection is not used.
Run a server in the background if it's absent.
When a server is running:
- If --skip-bsp-connection: return
- Else establish a bsp connection with the server and forward any message from the launcher stdin to the server and from the server to the launcher stdout.

Reuse server in the background

The launcher will always try to reuse a server already running or spawned by previous launcher executions to ensure that build servers are as hot and efficient as possible.

Use the launcher when off-line

The launcher is designed to be off-line friendly, e.g. if after running the launcher there is no internet connection, the launcher will not need to hit internet again and will instead populate data from caches. The launcher will fail fatally in off-line scenarios if and only if the server is not installed from the start.

Usage

Run the launcher manually

Clients can depend on the launcher and run it when they see fit. The flag --skip-bsp-connection is particularly useful for clients wishing to install and spawn a bloop version, but that do not wish to use BSP and instead prefer to detect manually the installed bloop version by the launcher and run the CLI.

Install the launcher

Version	Published	Resolver
1.3.0	06 Jun 2019 21:34	`-r sonatype:releases`
1.3.0+11-9ac20856+20190608-1823	08 Jun 2019 18:27	`-r bintray:scalacenter/releases`

The launcher is independent from bloop but it's released with the same cadence than the bloop build server. Therefore, you can expect a build server version to have an accompanying launcher version.

Open a BSP connection

To open a bsp a bsp connection with Bloop's build server you need to follow the Build Server Discovery protocol. BSP allow clients to connect to a BSP server in a build-tool-independent way through BSP connection files, a JSON file with build server metadata and an argv field that, if shelled out, will establish a bsp connection with a server.

The bloop BSP connection file is created automatically by any of the supported bloop installation methods (in the global .bsp directory) or by any of its build plugins (in the .bsp workspace directory). If you do not depend on a build plugin or require the installation of bloop, you are required to create a bloop BSP connection file to allow you and other servers follow the Build Server Protocol.