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Merge pull request #5012 from nvartolomei/nv/lb-first-or-random

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Add FIRST_OR_RANDOM Load Balancing policy
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alesapin 2019-04-18 18:54:04 +03:00 committed by GitHub
commit 214bf77b17
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4 changed files with 14 additions and 3 deletions
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1
dbms/programs/server/users.xml
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@ -16,6 +16,7 @@
with minimum number of different symbols between replica's hostname and local hostname
(Hamming distance).
in_order - first live replica is chosen in specified order.
first_or_random - if first replica one has higher number of errors, pick a random one from replicas with minimum number of errors.
-->
<load_balancing>random</load_balancing>
</default>

6
dbms/src/Client/ConnectionPoolWithFailover.cpp
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@ -62,6 +62,9 @@ IConnectionPool::Entry ConnectionPoolWithFailover::get(const Settings * settings
break;
case LoadBalancing::RANDOM:
break;
case LoadBalancing::FIRST_OR_RANDOM:
get_priority = [](size_t i) -> size_t { return i >= 1; };
break;
}
return Base::get(try_get_entry, get_priority);
@ -134,6 +137,9 @@ std::vector<ConnectionPoolWithFailover::TryResult> ConnectionPoolWithFailover::g
break;
case LoadBalancing::RANDOM:
break;
case LoadBalancing::FIRST_OR_RANDOM:
get_priority = [](size_t i) -> size_t { return i >= 1; };
break;
}
bool fallback_to_stale_replicas = settings ? bool(settings->fallback_to_stale_replicas_for_distributed_queries) : true;

7
dbms/src/Core/SettingsCommon.cpp
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@ -247,15 +247,16 @@ LoadBalancing SettingLoadBalancing::getLoadBalancing(const String & s)
if (s == "random") return LoadBalancing::RANDOM;
if (s == "nearest_hostname") return LoadBalancing::NEAREST_HOSTNAME;
if (s == "in_order") return LoadBalancing::IN_ORDER;
if (s == "first_or_random") return LoadBalancing::FIRST_OR_RANDOM;
throw Exception("Unknown load balancing mode: '" + s + "', must be one of 'random', 'nearest_hostname', 'in_order'",
throw Exception("Unknown load balancing mode: '" + s + "', must be one of 'random', 'nearest_hostname', 'in_order', 'first_or_random'",
ErrorCodes::UNKNOWN_LOAD_BALANCING);
}
String SettingLoadBalancing::toString() const
{
const char * strings[] = {"random", "nearest_hostname", "in_order"};
if (value < LoadBalancing::RANDOM || value > LoadBalancing::IN_ORDER)
const char * strings[] = {"random", "nearest_hostname", "in_order", "first_or_random"};
if (value < LoadBalancing::RANDOM || value > LoadBalancing::FIRST_OR_RANDOM)
throw Exception("Unknown load balancing mode", ErrorCodes::UNKNOWN_LOAD_BALANCING);
return strings[static_cast<size_t>(value)];
}

3
dbms/src/Core/SettingsCommon.h
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@ -167,6 +167,9 @@ enum class LoadBalancing
NEAREST_HOSTNAME,
/// replicas are walked through strictly in order; the number of errors does not matter
IN_ORDER,
/// if first replica one has higher number of errors,
/// pick a random one from replicas with minimum number of errors
FIRST_OR_RANDOM,
};
struct SettingLoadBalancing