ClickHouse/dbms/src/Interpreters/DNSCacheUpdater.cpp

55 lines
1.5 KiB
C++

#include "DNSCacheUpdater.h"
#include <Common/DNSResolver.h>
#include <Interpreters/Context.h>
#include <Core/BackgroundSchedulePool.h>
namespace DB
{
DNSCacheUpdater::DNSCacheUpdater(Context & context_, Int32 update_period_seconds_)
: context(context_),
update_period_seconds(update_period_seconds_),
pool(context_.getSchedulePool())
{
task_handle = pool.createTask("DNSCacheUpdater", [this]{ run(); });
}
void DNSCacheUpdater::run()
{
auto & resolver = DNSResolver::instance();
/// Reload cluster config if IP of any host has been changed since last update.
if (resolver.updateCache())
{
LOG_INFO(&Poco::Logger::get("DNSCacheUpdater"),
"IPs of some hosts have been changed. Will reload cluster config.");
try
{
context.reloadClusterConfig();
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
}
/** DNS resolution may take a while and by this reason, actual update period will be longer than update_period_seconds.
* We intentionally allow this "drift" for two reasons:
* - automatically throttle when DNS requests take longer time;
* - add natural randomization on huge clusters - avoid sending all requests at the same moment of time from different servers.
*/
task_handle->scheduleAfter(update_period_seconds * 1000);
}
void DNSCacheUpdater::start()
{
task_handle->activateAndSchedule();
}
DNSCacheUpdater::~DNSCacheUpdater()
{
task_handle->deactivate();
}
}