default max_burst equals to max_speed as in Throttler

docs/en/operations/system-tables/scheduler.md

@@ -38,8 +38,8 @@ inflight_requests: ᴺᵁᴸᴸ
 inflight_cost:     ᴺᵁᴸᴸ
 max_requests:      ᴺᵁᴸᴸ
 max_cost:          ᴺᵁᴸᴸ
-max_burst:         ᴺᵁᴸᴸ
 max_speed:         ᴺᵁᴸᴸ
+max_burst:         ᴺᵁᴸᴸ
 throttling_us:     ᴺᵁᴸᴸ
 tokens:            ᴺᵁᴸᴸ
 ```
@@ -66,7 +66,7 @@ Columns:
 - `inflight_cost` (`Nullable(Int64)`) - For `inflight_limit` nodes only. The sum of costs (e.g. bytes) of all resource requests dequeued from this node, that are currently in consumption state.
 - `max_requests` (`Nullable(Int64)`) - For `inflight_limit` nodes only. Upper limit for `inflight_requests` leading to constraint violation.
 - `max_cost` (`Nullable(Int64)`) - For `inflight_limit` nodes only. Upper limit for `inflight_cost` leading to constraint violation.
-- `max_burst` (`Nullable(Float64)`) - For `bandwidth_limit` nodes only. Upper limit for `tokens` available in token-bucket throttler.
 - `max_speed` (`Nullable(Float64)`) - For `bandwidth_limit` nodes only. Upper limit for bandwidth in tokens per second.
+- `max_burst` (`Nullable(Float64)`) - For `bandwidth_limit` nodes only. Upper limit for `tokens` available in token-bucket throttler.
 - `throttling_us` (`Nullable(Int64)`) - For `bandwidth_limit` nodes only. Total number of microseconds this node was in throttling state.
 - `tokens` (`Nullable(Float64)`) - For `bandwidth_limit` nodes only. Number of tokens currently available in token-bucket throttler.

docs/en/operations/workload-scheduling.md

@@ -79,7 +79,7 @@ graph TD
 
 **Possible node types:**
 * `inflight_limit` (constraint) - blocks if either number of concurrent in-flight requests exceeds `max_requests`, or their total cost exceeds `max_cost`; must have a single child.
-* `bandwidth_limit` (constraint) - blocks if burst exceeds `max_burst` (default 0) or current bandwidth exceeds `max_speed` (0 means unlimited); must have a single child.
+* `bandwidth_limit` (constraint) - blocks if current bandwidth exceeds `max_speed` (0 means unlimited) or burst exceeds `max_burst` (by default equals `max_speed`); must have a single child.
 * `fair` (policy) - selects the next request to serve from one of its children nodes according to max-min fairness; children nodes can specify `weight` (default is 1).
 * `priority` (policy) - selects the next request to serve from one of its children nodes according to static priorities (lower value means higher priority); children nodes can specify `priority` (default is 0).
 * `fifo` (queue) - leaf of the hierarchy capable of holding requests that exceed resource capacity.

src/IO/Resource/ThrottlerConstraint.h

@@ -18,10 +18,12 @@ namespace DB
 class ThrottlerConstraint : public ISchedulerConstraint
 {
 public:
+    static constexpr double default_burst_seconds = 1.0;
+
     ThrottlerConstraint(EventQueue * event_queue_, const Poco::Util::AbstractConfiguration & config = emptyConfig(), const String & config_prefix = {})
         : ISchedulerConstraint(event_queue_, config, config_prefix)
-        , max_burst(config.getDouble(config_prefix + ".max_burst", 0))
         , max_speed(config.getDouble(config_prefix + ".max_speed", 0))
+        , max_burst(config.getDouble(config_prefix + ".max_burst", default_burst_seconds * max_speed))
         , last_update(event_queue_->now())
         , tokens(max_burst)
     {}
@@ -37,7 +39,7 @@ public:
         if (!ISchedulerNode::equals(other))
             return false;
         if (auto * o = dynamic_cast<ThrottlerConstraint *>(other))
-            return max_burst == o->max_burst && max_speed == o->max_speed;
+            return max_speed == o->max_speed && max_burst == o->max_burst;
         return false;
     }
 
@@ -137,7 +139,7 @@ public:
 
     std::pair<double, double> getParams() const
     {
-        return {max_burst, max_speed};
+        return {max_speed, max_burst};
     }
 
 private:
@@ -184,8 +186,8 @@ private:
         return satisfied() && child_active;
     }
 
-    const double max_burst{0}; /// in tokens
     const double max_speed{0}; /// in tokens per second
+    const double max_burst{0}; /// in tokens
 
     EventQueue::TimePoint last_update;
     UInt64 postponed = EventQueue::not_postponed;

src/Storages/System/StorageSystemScheduler.cpp

@@ -41,8 +41,8 @@ NamesAndTypesList StorageSystemScheduler::getNamesAndTypes()
         {"inflight_cost", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeInt64>())},
         {"max_requests", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeInt64>())},
         {"max_cost", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeInt64>())},
-        {"max_burst", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeFloat64>())},
         {"max_speed", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeFloat64>())},
+        {"max_burst", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeFloat64>())},
         {"throttling_us", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeInt64>())},
         {"tokens", std::make_shared<DataTypeNullable>(std::make_shared<DataTypeFloat64>())},
     };
@@ -76,8 +76,8 @@ void StorageSystemScheduler::fillData(MutableColumns & res_columns, ContextPtr c
         Field inflight_cost;
         Field max_requests;
         Field max_cost;
-        Field max_burst;
         Field max_speed;
+        Field max_burst;
         Field throttling_us;
         Field tokens;
 
@@ -101,7 +101,7 @@ void StorageSystemScheduler::fillData(MutableColumns & res_columns, ContextPtr c
         }
         if (auto * ptr = dynamic_cast<ThrottlerConstraint *>(node.get()))
         {
-            std::tie(max_burst, max_speed) = ptr->getParams();
+            std::tie(max_speed, max_burst) = ptr->getParams();
             throttling_us = ptr->getThrottlingDuration().count() / 1000;
             tokens = ptr->getTokens();
         }
@@ -116,8 +116,8 @@ void StorageSystemScheduler::fillData(MutableColumns & res_columns, ContextPtr c
         res_columns[i++]->insert(inflight_cost);
         res_columns[i++]->insert(max_requests);
         res_columns[i++]->insert(max_cost);
-        res_columns[i++]->insert(max_burst);
         res_columns[i++]->insert(max_speed);
+        res_columns[i++]->insert(max_burst);
         res_columns[i++]->insert(throttling_us);
         res_columns[i++]->insert(tokens);
     });