* Alerting: Prevent short uid collision in legacy migration when db is case-insensitive
Two factors come into play that cause sporadic uid conflicts during legacy alert migration:
- MySQL and MySQL-compatible backends use case-insensitive collation.
- Our short uid generator is not a uniform RNG and generates uids in such a way that generations in quick succession have a higher probability of creating similar uids.
Normally we would be guaranteed unique short uid generation, however if the source alphabet contains
duplicate characters (for example, if we use case-insensitive comparison) this guarantee is void.
Generating even ~1000 uids in quick succession is nearly guaranteed to create a case-insensitive
duplicate.
* Alerting: Create fewer contact points on migration
Previously a new contact point was created for every unique combination
of channels attached to any legacy alert. This was very hard to maintain,
requiring modifications in every generated contact point.
This change deduplicates the generated contact points to a more
reasonable state. There should now only be one contact point per legacy
channel, and we attached multiple contact points to a route by nesting
them. The sole exception to this is if there were multiple default
legacy channels, in which case we create a redundant contact point
containing all of them used only in the root policy. This allows for a
much simpler notification policy structure.
Co-authored-by: gotjosh <josue.abreu@gmail.com>
* Alerting: Validate contact point configuration during the migration
This minimises the chances of generating broken configuration as part of the migration. Originally, we wanted to generate it and not produce a hard stop in Grafana but this strategy has the chance to avoid delivering notifications for our users.
We now think it's better to hard stop the migration and let the user take care of resolving the configuration manually.
