Add instructions to alerting guidance

[piyush-singh]

Piyush Singh (piyush-singh) commented:

While attempting to reproduce a customer issue that was reported to support, I followed our Prometheus and Alertmanager configuration guidance. There are a few issues in the doc as written:

1. (nit) The default config file for Alertmanager has be renamed from simple.yml to alertmanager.yml
2. By default, our prometheus.yml file includes a "path prefix". Our instructions for starting Alertmanager do not configure Alertmanager to serve from this path prefix. In order to do so, we would need to run Alertmanager using a command that adds a flag: alertmanager --config.file=alertmanager.yml --web.external-url=http://localhost:9093/alertmanager. Note that if we add this path prefix, the remaining URLs in the doc will also need to be updated. Alternatively, we could simply remove this path prefix from the prometheus.yml file and instead set it as - path_prefix: "".

Jira Issue: DOC-788

[taroface]

Hi @bobvawter, can you comment on whether it would be safe to set path_prefix to "" in the Prometheus config, or does the value need to be "/alertmanager/" for other reasons?

[taroface]

@bobvawter Ping on this question! Thanks.