amlint for VS Code

Catch Prometheus Alertmanager config mistakes while you edit: alerts that reach no receiver, routes that never match, inhibit rules that mute too much. Hover a route to see where its alerts go.

The extension runs amlint, an open-source linter for Alertmanager configs. It catches what amtool check-config catches, plus configs that load fine but don't route the way you meant.

Features

Findings as you type. The same findings as amlint check, on the same lines. amlint lints the editor buffer, so you don't have to save first. Click a check code to read what goes wrong and how to fix it.

Hover a route to see:

• its matchers, and the matchers on the way to it
• its receiver, group_by and timings, and where each comes from: set here, inherited from a parent route, or Alertmanager's default
• an example alert that ends on this route, and the receivers it goes to. The example comes from amlint's routing simulation, the same one behind amlint route.

Quick fixes. Silence a finding you accept: add # amlint: disable=<code> to its line, or # amlint: disable-file=<code> to the top of the file.

Reads the file you deploy. A plain alertmanager.yml, a Kubernetes Secret or ConfigMap, kube-prometheus-stack Helm values, a Mimir or Cortex tenant config, or prometheus-operator AlertmanagerConfig resources. Findings point into your file, even inside an embedded alertmanager.yaml: | block.

Requirements

amlint 0.6.0 or newer, which has the amlint lsp command:

pip install -U amlint

Check that it works: amlint lsp --help. If VS Code can't find amlint on its PATH, set amlint.path to the full path, for example ${workspaceFolder}/.venv/bin/amlint.

Which files it lints

Every YAML file that holds an Alertmanager config:

• a document with route: or receivers: at the top
• a Secret or ConfigMap with an alertmanager.yaml key
• Helm values with an alertmanager: section, or a Mimir config with alertmanager_config:
• AlertmanagerConfig resources

Other YAML files, such as Kubernetes manifests or Prometheus rule files, get no findings.

Settings

In an untrusted workspace, amlint.path comes from your user settings only.

To ignore checks or change their severity for a whole repository, use .amlint.yml in the workspace folder, as for the CLI. amlint re-lints open files when it changes:

# .amlint.yml
ignore: [empty-receiver]
severity:
  unused-receiver: error

Commands

• amlint: Restart Server: restart amlint lsp, for example after upgrading amlint.

Troubleshooting

• "could not start amlint lsp": amlint isn't installed, isn't on VS Code's PATH, or is older than 0.6.0. Run which amlint in a terminal and put that path in amlint.path.
• No findings in a config: check that the file's language mode (bottom right) is YAML. Then set amlint.trace.server to messages and look at the amlint output channel.

Links

• Docs: every check, with examples and fixes
• Editor setup, including Neovim and Helix
• Playground: try amlint in the browser
• Issues