Extract configuration into a new struct batchlog_manager_config and have the
callers populate it using db::config. This reduces dependencies on global objects.
std::random_device() uses the relatively slow /dev/urandom, and we rarely if
ever intend to use it directly - we normally want to use it to seed a faster
random_engine (a pseudo-random number generator).
In many places in the code, we first created a random_device variable, and then
using it created a random_engine variable. However, this practice created the
risk of a programmer accidentally using the random_device object, instead of the
random_engine object, because both have the same API; This hurts performance.
This risk materialized in just two places in the code, utils/uuid.cc and
gms/gossiper.cc. A patch for to uuid.cc was sent previously by Pawel and is
not included in this patch, and the fix for gossiper.{cc,hh} is included here.
To avoid risking the same mistake in the future, this patch switches across the
code to an idiom where the random_device object is not *named*, so cannot be
accidentally used. We use the following idiom:
std::default_random_engine _engine{std::random_device{}()};
Here std::random_device{}() creates the random device (/dev/urandom) and pulls
a random integer from it. It then uses this seed to create the random_engine
(the pseudo-random number generator). The std::random_device{} object is
temporary and unnamed, and cannot be unintentionally used directly.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20180726154958.4405-1-nyh@scylladb.com>
* seastar f14d2a3...7a49ae5 (8):
> sharded: improve support for cooperating sharded<> services
> sharded: support for peer services
> semaphore: add a version of with_semaphore that takes a duration timeout
> scripts: perftune.py: fix the CPU mask generation for more than 64 CPUs
> Revert "future-utils: make when_all() (vector variant) exception safe"
> Revert "future-utils: fix gross compilation errors in when_all()"
> future-utils: fix gross compilation errors in when_all()
> future-utils: make when_all() (vector variant) exception safe
Includes change to batchlog_manager constructor to adapt it to
seastar::sharded::start() change.
During decommission, the storage_service::unbootstrap() needs to
initiate a batchlog replay operation. To sync the replay operation
initiated by the timer in batchlog_manager and storage_service, a
semaphore is introduced. To simplify the semaphore locking, the
management code now always runs on shard zero, but the real work is
distruted to all shards.
Somewhat simplifies version of the Origin code, since from what I
can see, there is less need for us to do explicit query sends in
the BLM itself, instead we can just go through storage_proxy.
I could be wrong though.
