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