fix(web): guard against division by zero and nil in metrics handlers - #299
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The metrics handlers in the applications LiveView could crash with an
ArithmeticError when dividing by zero or nil:
- handle_info({:update_system_info, ...}) divided by host_info.memory_total,
which is nil | non_neg_integer() per Host.Info. A nil or 0 value crashed
the LiveView process.
- handle_info({:metrics_new_data, ...}) divided by the metric limit. A node
reporting limit: 0 crashed the LiveView process.
Add guards to both handlers so they skip the metric update when the divisor
is nil or 0, and add a fallback clause for update_system_info that still
updates host_info without computing the memory percentage.
Risk assessment:
- Impact: the applications LiveView no longer crashes when host memory info
is incomplete or a VM metric reports a zero limit
- Blast radius: deployex_web applications LiveView only; no other handlers
or apps are touched
- Regression risk: low - the guards only skip the percentage computation in
edge cases that previously crashed; normal values are unaffected
- Rollback: plain commit revert
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Summary
handle_info({:update_system_info, ...})divided byhost_info.memory_total, which isnil | non_neg_integer()perHost.Info. A nil or 0 value crashed the LiveView process withArithmeticError.handle_info({:metrics_new_data, ...})divided by the metric limit. A node reportinglimit: 0crashed the LiveView process.update_system_infothat still updateshost_infowithout computing the memory percentage.Test plan
mix test apps/deployex_web/test/deployex_web/live/applications/index_test.exs --warnings-as-errors(20 tests)mix format --check-formattedmix credo --strict apps/deployex_web/lib/deployex_web/live/applications/index.exRisk assessment
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