4498. [test] Simplify prerequisite checks in system tests.
[RT #43516]
(cherry picked from commit 5480a74b70)
(cherry picked from commit 45fd95544c)
(cherry picked from commit 6e09e18400)
3938. [func] Added quotas to be used in recursive resolvers
that are under high query load for names in zones
whose authoritative servers are nonresponsive or
are experiencing a denial of service attack.
- "fetches-per-server" limits the number of
simultaneous queries that can be sent to any
single authoritative server. The configured
value is a starting point; it is automatically
adjusted downward if the server is partially or
completely non-responsive. The algorithm used to
adjust the quota can be configured via the
"fetch-quota-params" option.
- "fetches-per-zone" limits the number of
simultaneous queries that can be sent for names
within a single domain. (Note: Unlike
"fetches-per-server", this value is not
self-tuning.)
- New stats counters have been added to count
queries spilled due to these quotas.
These options are not available by default;
use "configure --enable-fetchlimit" (or
--enable-developer) to include them in the build.
See the ARM for details of these options. [RT #37125]
