wilfred-s commented on code in PR #562: URL: https://github.com/apache/yunikorn-core/pull/562#discussion_r1246180538
########## pkg/events/event_ringbuffer.go: ########## @@ -0,0 +1,220 @@ +/* + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. +*/ + +package events + +import ( + "math" + "sync" + + "github.com/apache/yunikorn-scheduler-interface/lib/go/si" +) + +type eventRange struct { + start uint64 + end uint64 +} + +// eventRingBuffer A specialized circular buffer to store event objects. +// +// Unlike to regular circular buffers, existing entries are never directly removed and new entries can be added if the buffer is full. +// In this case, the oldest entry is overwritten and can be collected by the GC. +// Each event has an ID, however, this mapping is not stored directly. If needed, we calculate the id +// of the event based on slice positions. +// +// Retrieving the records can be achieved with GetEventsFromID and GetRecentEntries. +type eventRingBuffer struct { + events []*si.EventRecord + capacity uint64 // capacity of the buffer, never changes + head uint64 // position of the next element (no tail since we don't remove elements) + full bool // indicates whether the buffer if full - once it is, it stays full + id uint64 // unique id of an event record + + sync.RWMutex +} + +// Add adds an event to the ring buffer. If the buffer is full, the oldest element is overwritten. +// This method never fails. +func (e *eventRingBuffer) Add(event *si.EventRecord) { + e.Lock() + defer e.Unlock() + + e.events[e.head] = event + if !e.full { + e.full = e.head == e.capacity-1 + } + e.head = (e.head + 1) % e.capacity + e.id++ +} + +func (e *eventRingBuffer) GetEventsFromID(id uint64, count uint64) ([]*si.EventRecord, uint64) { + e.RLock() + defer e.RUnlock() + lowest := e.getLowestId() + + pos, idFound := e.id2pos(id) + if !idFound { + return nil, lowest + } + + if e.full && pos > e.head { + r1 := &eventRange{ + start: pos, + end: e.capacity, + } + r2 := &eventRange{ + start: 0, + end: e.head, + } + return e.getEntriesFromRanges(r1, r2, count), lowest + } + + end := e.head + if e.full && e.head == 0 { + // Special case: buffer is full and head is pointing at the beginning. + // Need to set explicitly to get [0..capacity] range because e.head + // never points to e.capacity. + end = e.capacity + } + return e.getEntriesFromRanges(&eventRange{ + start: pos, + end: end, + }, nil, count), lowest Review Comment: `getEntriesFromRange()` can then be as simple as it was a couple of days ago without all the count handling and ignoring the second range if limited by count -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
