After change 5995, zone transfers were using a small
compression context that only had space for the first
few dozen names in each message. They now use a large
compression context with enough space for every name.
The "final reference detached" message was meant to be DEBUG(1), but was
instead kept at INFO level. Move it to the DEBUG(1) logging level, so
it's not printed under normal operations.
Currently, the ADB uses TTL of 0 for ADB names that the server is
authoritative for and TTL of 10 seconds for HINT and GLUE ADB names.
This requires the unlinked ADB entries to be kept around, because they
would disappear too quickly. This especially affect the root zone as
the trust level is "ultimate" for the root zone nameservers.
This commit restores the ability to keep the unlinked ADB entries in the
database for later reuse, restores printing the unlinked entries and
adds some extra cleaning of the unlinked ADB entries on the tail of the
LRU list (similar to what we are doing for the ADB names).
The dns_adb unit has been refactored to be much simpler. Following
changes have been made:
1. Simplify the ADB to always allow GLUE and hints
There were only two places where dns_adb_createfind() was used - in
the dns_resolver unit where hints and GLUE addresses were ok, and in
the dns_zone where dns_adb_createfind() would be called without
DNS_ADBFIND_HINTOK and DNS_ADBFIND_GLUEOK set.
Simplify the logic by allowing hint and GLUE addresses when looking
up the nameserver addresses to notify. The difference is negligible
and would cause a difference in the notified addresses only when
there's mismatch between the parent and child addresses and we
haven't cached the child addresses yet.
2. Drop the namebuckets and entrybuckets
Formerly, the namebuckets and entrybuckets were used to reduced the
lock contention when accessing the double-linked lists stored in each
bucket. In the previous refactoring, the custom hashtable for the
buckets has been replaced with isc_ht/isc_hashmap, so only a single
item (mostly, see below) would end up in each bucket.
Removing the entrybuckets has been straightforward, the only matching
was done on the isc_sockaddr_t member of the dns_adbentry.
Removing the zonebuckets required GLUEOK and HINTOK bits to be
removed because the find could match entries with-or-without the bits
set, and creating a custom key that stores the
DNS_ADBFIND_STARTATZONE in the first byte of the key, so we can do a
straightforward lookup into the hashtable without traversing a list
that contains items with different flags.
3. Remove unassociated entries from ADB database
Previously, the adbentries could live in the ADB database even after
unlinking them from dns_adbnames. Such entries would show up as
"Unassociated entries" in the ADB dump. The benefit of keeping such
entries is little - the chance that we link such entry to a adbname
is small, and it's simpler to evict unlinked entries from the ADB
cache (and the hashtable) than create second LRU cleaning mechanism.
Unlinked ADB entries are now directly deleted from the hash
table (hashmap) upon destruction.
4. Cleanup expired entries from the hash table
When buckets were still in place, the code would keep the buckets
always allocated and never shrink the hash table (hashmap). With
proper reference counting in place, we can delete the adbnames from
the hash table and the LRU list.
5. Stop purging the names early when we hit the time limit
Because the LRU list is now time ordered, we can stop purging the
names when we find a first entry that doesn't fullfil our time-based
eviction criteria because no further entry on the LRU list will meet
the criteria.
Future work:
1. Lock contention
In this commit, the focus was on correctness of the data structure,
but in the future, the lock contention in the ADB database needs to
be addressed. Currently, we use simple mutex to lock the hash
tables, because we almost always need to use a write lock for
properly purging the hashtables. The ADB database needs to be
sharded (similar to the effect that buckets had in the past). Each
shard would contain own hashmap and own LRU list.
2. Time-based purging
The ADB names and entries stay intact when there are no lookups.
When we add separate shards, a timer needs to be added for time-based
cleaning in case there's no traffic hashing to the inactive shard.
3. Revisit the 30 minutes limit
The ADB cache is capped at 30 minutes. This needs to be revisited,
and at least the limit should be configurable (in both directions).
The dns_adb would serialize all fetches on a single task. Create a
per-thread task, so the fetches will stay local to the thread that
initiated the fetch.
Before the refactoring, there was only few buckets with many names in
them, so cleaning up stale ADB names per-bucket made sense. After the
refactoring, each bucket directly maps to ADB name, so purging has been
effectively disabled.
Create a global LRU list for ADB names (and ADB entries) and purge the
stale ADB names globally.
Previously, the name and entry buckets were much larger, so the dead
names and entries were moved to a secondary list to be cleaned
later (f.e. after the already running fetch has been canceled). After
the last refactoring, the bucket now contains only the name (entry)
itself and thus the extra list has a little use. Remove the .deadnames
and .deadentries from dns_adbnamebucket_t and dns_adbentrybucket_t
structures.
The dns_rpz_zones structure was using .refs and .irefs for strong and
weak reference counting. Rewrite the unit to use just a single
reference counting + shutdown sequence (dns_rpz_destroy_rpzs) that must
be called by the creator of the dns_rpz_zones_t object. Remove the
reference counting from the dns_rpz_zone structure as it is not needed
because the zone objects are fully embedded into the dns_rpz_zones
structure and dns_rpz_zones_t object must never be destroyed before all
dns_rpz_zone_t objects.
The dns_rps_zones_t reference counting uses the new ISC_REFCOUNT_TRACE
capability - enable by defining DNS_RPZ_TRACE in the dns/rpz.h header.
Additionally, add magic numbers to the dns_rpz_zone and dns_rpz_zones
structures.
The new ISC_REFCOUNT_TRACE_{IMPL,DECL} macros can be used to add a
reference tracing capability to any unit using the reference counting.
It requires a little bit of extra work in each header as you can't have
a define from inside a define (see rpz.h), but it's fairly easy to add
tracing to any struct using reference counting with these macros.
The dns_cache API contained a cache cleaning mechanism that would be
disabled for 'rbt' based cache. As named doesn't have any other cache
implementations, remove the cache cleaning mechanism from dns_cache API.
The RBTDB has own cache cleaning mechanism and therefor the iterator
.cleaning member would never be set to true. Remove the code that
checks for iterator->cleaning from the RBTDB.
This commit make TCP code use uv_try_write() on best effort basis,
just like TCP DNS and TLS DNS code does.
This optimisation was added in
'caa5b6548a11da6ca772d6f7e10db3a164a18f8d' but, similar change was
mistakenly omitted for generic TCP code. This commit fixes that.
The `gen` program was causing a lengthy single-threaded pause in
the BIND build. When generating RDATATYPE_FROMTEXT_SW(), `gen` hit
the inner loop of `find_typename()` over 1.2 billion times. This
change avoids long deeply-nested loops, so `gen` now runs in less
than 10ms, about 300x faster.
No changes to the output.
Don't restart reading in the send callback after the httpdmgr has been
shut down, and call httpd_request(..., ISC_R_SHUTDOWN, ...) when
shutting down the httpdmgr to reduce code duplication.
Previously, the send callback would be synchronous only on success. Add
an option (similar to what other callbacks have) to decide whether we
need the asynchronous send callback on a higher level.
On a general level, we need the asynchronous callbacks to happen only
when we are invoking the callback from the public API. If the path to
the callback went through the libuv callback or netmgr callback, we are
already on asynchronous path, and there's no need to make the call to
the callback asynchronous again.
For the send callback, this means we need the asynchronous path for
failure paths inside the isc_nm_send() (which calls isc__nm_udp_send(),
isc__nm_tcp_send(), etc...) - all other invocations of the send callback
could be synchronous, because those are called from the respective libuv
send callbacks.
Previously, the read callback would be synchronous only on success or
timeout. Add an option (similar to what other callbacks have) to decide
whether we need the asynchronous read callback on a higher level.
On a general level, we need the asynchronous callbacks to happen only
when we are invoking the callback from the public API. If the path to
the callback went through the libuv callback or netmgr callback, we are
already on asynchronous path, and there's no need to make the call to
the callback asynchronous again.
For the read callback, this means we need the asynchronous path for
failure paths inside the isc_nm_read() (which calls isc__nm_udp_read(),
isc__nm_tcp_read(), etc...) - all other invocations of the read callback
could be synchronous, because those are called from the respective libuv
or netmgr read callbacks.
The various factors like NS_PER_MS are now defined in a single place
and the names are no longer inconsistent. I chose the _PER_SEC names
rather than _PER_S because it is slightly more clear in isolation;
but the smaller units are always NS, US, and MS.
The system test should never attempt to start or stop any other server
than those that belong to that system test. Therefore, it is not
necessary to specify the system test name in function calls.
Additionally, this makes it possible to run the test inside a
differently named directory, as its name is automatically detected with
the $SYSTESTDIR variable. This enables running the system tests inside a
temporary directory.
Direct use of stop.pl was replaced with a more systematic approach to
use stop_servers helper function.
Extract the tlss values if present from the ipkeylist entry and add
the resulting tls setting to the constructed configuration for the
primary.
When comparing catalog zone entries for reuse also check the
masters.tlss values for equality.
the 'nupdates' field was originally used to track whether a client
was ready to shut down, along with other similar counters nreads,
nrecvs, naccepts and nsends. this is now tracked differently, but
nupdates was overlooked when the other counters were removed.
