This prevents the use of DependencyGroup for storing the dependencies during
the early registration (m_DependencyGroupsPushedToRegistry = false),
m_PendingDependencies is introduced as a replacement to store the dependencies
at that time.
Previously the dependency state was evaluated by picking the first
dependency object from the batched members. However, since the
dependency `disable_{checks,notifications` attributes aren't taken into
account when batching the members, the evaluated state may yield a wrong
result for some Checkables due to some random dependency from other
Checkable of that group that has the `disable_{checks,notifications`
attrs set. This commit forces the callers to always provide the child
Checkable the state is evaluated for and picks only the dependency
objects of that child Checkable.
`checkable` is already added to the set by the insert call above, so calling
emplace for the same checkable doesn't do anything useful and can be removed.
The previous wasn't per-se wrong, but it was way too inefficient. With
this commit each and every Checkable is going to be visited only once,
and we won't traverse the same Checkable's children multiple times
somewhere in the dependency chain.
The previous limit (32) doesn't seem to make sense, and appears to be some random number.
So, this limit is set to 256 to match the limit in IsReachable().
Traditional behaviour was to regard all dependecies as cumulative (e.g., the parent considered unreachable if any one dependency is violated), commit ed5892238916ab667a4c9d904bd73acd3ed162f2 made all dependencies regarded redundant (e.g., the parent considered unreachable only if all dependency are violated). This may lead to unrelated services (or even hosts vs. services) inadvertantly regarded to be redundant to each other.
Most importantly, applying the explicit "disable-host-service-checks" dependency described in the "Monitoring Basics" chapter will defeat all other dependencies.
This commit introduces a new "redundancy_group" attribute for dependencies.
Specifying a redundancy_group causes a dependency to be regarded as redundant only inside that redundancy group.
Dependencies lacking a redundancy_group attribute are regarded as essential for the parent.
This allows for both cumulative and redundant dependencies and even a combination (cumulation of redundancies, like SSH depeding on both LDAP and DNS to function, while operating redundant LDAP servers as well as redundant DNS resolvers).
This commit lacks changes to the tests.
What does this change?
* Remove use of spaces for formatting
These could be found by using `grep -r -l -P '^\t+ +[^*]'
* Removal of training whitespaces
* A few lines longer than 120 chars
