Malachi.
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The one surface a boot precondition uses to refuse a start: one line through Malachi.I18n, the
same line on stderr, and a halt with a distinct exit status.
Two gates need it. Malachi.Storage.FormatMarker refuses a data directory written in a format this
binary cannot read (#189), and Malachi.Cluster.ClusterFlags refuses a node whose capability set
lacks a flag the cluster has already enabled (#193). Both say the same three things in the same
order, so they say them here.
The line goes to the logger and to stderr because a container log shows the second even when the logger has not flushed, which is the only output an operator gets from a node that halts during boot.
halt_fun is the seam: production passes System.halt/1, a test passes a function that records the
status instead of taking the VM down with it.
Summary
Functions
The exit status of a refused start (78, EX_CONFIG).
Refuses the start: logs detail inside the standard envelope, prints the same line on stderr, and
halts with exit_status/0 through halt_fun.
Functions
@spec exit_status() :: non_neg_integer()
The exit status of a refused start (78, EX_CONFIG).
@spec refuse!(String.t(), (non_neg_integer() -> any())) :: any()
Refuses the start: logs detail inside the standard envelope, prints the same line on stderr, and
halts with exit_status/0 through halt_fun.
detail is already a rendered I18n string, because only the caller knows which key describes its
own precondition. The envelope around it is the same for every gate, which is what makes a refused
start recognizable by its first words whatever refused it.