Having created log-based metrics in cloud console, I then want to create alerts so that every time there is a new matching log entry, the alert triggers.
In trying to create a suitable metric, the most likely looking options seem to be threshold or rate of change, but I don't think either will work for a policy of 1 log message => 1 alert.
Help appreciated.
You can use another alert triggering software (like PagerDuty) which is pinged by emails sent by Stackdriver. PagerDuty is able to filter all those emails that has the word RESOLVE in its subject. They can be absolutely thrown away in our case if you'd like to avoid autoresolving. Of course Stackdriver and PagerDuty alerts will diverge from each other (states will be inconsistent) but you should consider PD as single source of truth this time. It could be a possible workaround.
With log-based alerts, we can create alerts from the logs, incident will be creatied for each matching entry.
https://cloud.google.com/blog/products/operations/create-logs-alerts-preview
