emqx4.3/apps/emqx_machine

EMQX machine

This application manages other OTP applications in EMQX and serves as the entry point when BEAM VM starts up. It prepares the node before starting mnesia/mria, as well as EMQX business logic. It keeps track of the business applications storing data in Mnesia, which need to be restarted when the node joins the cluster by registering ekka callbacks. Also it kicks off autoclustering (EMQX cluster discovery) on the core nodes.

emqx_machine application doesn't do much on its own, but it facilitates the environment for running other EMQX applications.

Features

Global GC

emqx_global_gc is a gen_server that forces garbage collection of all Erlang processes running in the BEAM VM. This is meant to save the RAM.

Restricted shell

emqx_restricted_shell module prevents user from accidentally issuing Erlang shell commands that can stop the remote node.

Signal handler

emqx_machine_signal_handler handles POSIX signals sent to BEAM VM process. It helps to shut down EMQX broker gracefully when it receives SIGTERM signal.

Cover

emqx_cover is a helper module that helps to collect coverage reports during testing.

Limitation

Currently emqx_machine boots the business apps before starting autocluster, so a fresh node joining the cluster actually starts business application twice: first in the singleton mode, and then in clustered mode.

Documentation links

Configuration: node.global_gc_interval

Configurations

The following application environment variables are used:

• emqx_machine.global_gc_interval: interval at which global GC is run
• emqx_machine.custom_shard_transports: contains a map that allows to fine tune transport (rpc or gen_rpc) used to send Mria transactions from the core node to the replicant
• emqx_machine.backtrace_depth: set maximum depth of Erlang stacktraces in crash reports

Contributing

Please see our contributing.md.