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#include "DNSCacheUpdater.h"
#include <Interpreters/Context.h>
#include <Common/DNSResolver.h>
#include <Common/logger_useful.h>
namespace DB
{
DNSCacheUpdater::DNSCacheUpdater(ContextPtr context_, Int32 update_period_seconds_, UInt32 max_consecutive_failures_)
: WithContext(context_)
, update_period_seconds(update_period_seconds_)
, max_consecutive_failures(max_consecutive_failures_)
, pool(getContext()->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(max_consecutive_failures))
{
LOG_INFO(&Poco::Logger::get("DNSCacheUpdater"), "IPs of some hosts have been changed. Will reload cluster config.");
try
{
getContext()->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(static_cast<size_t>(update_period_seconds) * 1000);
}
void DNSCacheUpdater::start()
{
LOG_INFO(&Poco::Logger::get("DNSCacheUpdater"), "Update period {} seconds", update_period_seconds);
task_handle->activateAndSchedule();
}
DNSCacheUpdater::~DNSCacheUpdater()
{
task_handle->deactivate();
}
}
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