This allows for a faster config load due to less locking required.
The change is slightly backwards-incompatible. Before, you could manipulate the
globals namespace at a later stage, but disallowing this feels reasonable for
the performance benefit alone (which especially shows on many-core machines).
Apart from that, it's doubtful if doing so is even useful at all as the DSL
provides no mechanism for you to synchronize your operations that may run in
parallel. The data structures itself are protected from race conditions, but
anything implemented on top of this may still be subject to race conditions.
And even if some user has a good reason for doing this, there's a feasible
workaround by creating your own namespace like globals.mutable and using that
instead.
If a connection hangs for too long in ApiListener#NewClientHandler(),
ApiListener#AddConnection()'s Timeout calls boost::asio::basic_socket#cancel()
on that connection to trigger an exception which unwinds
ApiListener#NewClientHandler(). Previously that unwind could trigger a Defer
which called boost::asio::ssl::stream#async_shutdown() which extended the hang.
Normally if for some reason an ack comment still exists on a checkable not
acked anymore, still clean it up. But while replaying log config objects
incl. ack comments come before check results and acks. I.e. 1) ack comment,
2) DOWN check result and 3) ack. Not 1) DOWN check result, 2) ack and 3) ack
comment. So the checkable is temporarily not acked, but already has the ack
comment. In this case the DOWN check result which is older than the ack
comment shall not clean up the latter.
Traditional behaviour was to regard all dependecies as cumulative (e.g., the parent considered unreachable if any one dependency is violated), commit ed58922389 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.
Alexander A. Klimov
Julian Brost
Silas
Mattia Codato
Edgar Fuß