The check makes no attempt to explicitly connect to Redis, it uses the
connection of the IcingaDB feature, so this message better describes the state
in this situation.
IcingaDB::GetConnection() uses IcingaDB::m_Rcon which is only initialized in
IcingaDB::Start(), therefore add a nullptr check to the check command.
Additionally, as m_Rcon is potentially accessed concurrently, add a copy of the
value that is safe for concurrent use.
icingadb-web shows multiple lines from the check output collapsed into a single
line. The lines containing just minuses make this look cluttered and making
making it a heading provides little to no benefit. Even when rendering markdown
in the check output at some point, having the lists labeled using normal
paragraphs would look just fine.
- Add icinga2_ and icingadb_ prefixes to make clear which component is
responsible for the value.
- Rename heartbeat_lag to heartbeat_age, describes it better in my opinion and
sound a bit less like something that should be as close to zero as possible.
- Rename redis_dump/database_sync into full_dump/full_sync as this is how these
operations are refered to in log messages as well.
- Rename Redis backlog into Redis query backlog, makes it a bit clearer in my
opinion.
- Rename runtime_backlog into runtime_update_backlog, as the component in
Icinga DB is called that way and this naming is also exposed in log messages.
- Rename dump_config/state/history into config/state/history_dump, makes it
sound more natural.
They add no additional information compared to the *_1min values as it's always
the same value divided by 60 anyways. Adding the actual value from the last
second makes little sense for realistic values of check_interval.
Use the already existing format to pass performance data to Icinga 2 rather
than some new JSON structure. Has the additional benefit of doing more things
in Go than in C++.
