1 | #include "DNSCacheUpdater.h" |
---|---|
2 | #include <Common/DNSResolver.h> |
3 | #include <Interpreters/Context.h> |
4 | #include <Core/BackgroundSchedulePool.h> |
5 | |
6 | namespace DB |
7 | { |
8 | |
9 | DNSCacheUpdater::DNSCacheUpdater(Context & context_, Int32 update_period_seconds_) |
10 | : context(context_), |
11 | update_period_seconds(update_period_seconds_), |
12 | pool(context_.getSchedulePool()) |
13 | { |
14 | task_handle = pool.createTask("DNSCacheUpdater", [this]{ run(); }); |
15 | } |
16 | |
17 | void DNSCacheUpdater::run() |
18 | { |
19 | auto & resolver = DNSResolver::instance(); |
20 | |
21 | /// Reload cluster config if IP of any host has been changed since last update. |
22 | if (resolver.updateCache()) |
23 | { |
24 | LOG_INFO(&Poco::Logger::get("DNSCacheUpdater"), |
25 | "IPs of some hosts have been changed. Will reload cluster config."); |
26 | try |
27 | { |
28 | context.reloadClusterConfig(); |
29 | } |
30 | catch (...) |
31 | { |
32 | tryLogCurrentException(__PRETTY_FUNCTION__); |
33 | } |
34 | } |
35 | |
36 | /** DNS resolution may take a while and by this reason, actual update period will be longer than update_period_seconds. |
37 | * We intentionally allow this "drift" for two reasons: |
38 | * - automatically throttle when DNS requests take longer time; |
39 | * - add natural randomization on huge clusters - avoid sending all requests at the same moment of time from different servers. |
40 | */ |
41 | task_handle->scheduleAfter(update_period_seconds * 1000); |
42 | } |
43 | |
44 | void DNSCacheUpdater::start() |
45 | { |
46 | task_handle->activateAndSchedule(); |
47 | } |
48 | |
49 | DNSCacheUpdater::~DNSCacheUpdater() |
50 | { |
51 | task_handle->deactivate(); |
52 | } |
53 | |
54 | } |
55 |