wilfred-s commented on code in PR #562: URL: https://github.com/apache/yunikorn-core/pull/562#discussion_r1241840039
########## pkg/events/event_ringbuffer.go: ########## @@ -0,0 +1,213 @@ +/* + 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 ( + "sync" + + "github.com/apache/yunikorn-scheduler-interface/lib/go/si" +) + +type resultState int + +const ( + resultOK resultState = iota + bufferEmpty + idNotFound +) + +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. +// +// Retrieving the records can be achieved with GetEventsFromID and GetRecentEntries. +type eventRingBuffer struct { + events []*si.EventRecord + capacity uint64 + idx uint64 + full bool + + id uint64 // increasing unique id + startId uint64 // id of the message at index 0 + lowestId uint64 // the lowest available id in the buffer (pointed at by e.idx when full) + + sync.RWMutex +} + +// Add adds an event to the ring buffer. If the buffer is full, the oldest element is overwritten. +// This method never fails. +// Each event has an ID, however, this mapping is not stored directly. Instead, we store the starting ID at +// index 0 and the lowest available ID. +func (e *eventRingBuffer) Add(event *si.EventRecord) { + e.Lock() + defer e.Unlock() + + e.events[e.idx] = event + if e.idx == 0 { + e.startId = e.id + } + if e.idx == e.capacity-1 { + e.full = true + } + e.idx = (e.idx + 1) % e.capacity + if e.full { + // once the buffer becomes full, we keep incrementing this value + // this is the id of the element which is about to be overwritten in the next Add() call + e.lowestId++ + } + + e.id++ +} + +func (e *eventRingBuffer) GetEventsFromID(id uint64) ([]*si.EventRecord, resultState) { + e.RLock() + defer e.RUnlock() + + storedId, state := e.id2pos(id) + if state != resultOK { + return nil, state + } + + if e.full { + r1 := &eventRange{ + start: storedId, + end: e.capacity, + } + r2 := &eventRange{ + start: 0, + end: e.idx, + } + return e.getEntriesFromRanges(r1, r2), resultOK + } + + return e.getEntriesFromRanges(&eventRange{ + start: storedId, + end: e.idx, + }, nil), resultOK +} + +func (e *eventRingBuffer) GetRecentEntries(count uint64) ([]*si.EventRecord, uint64, resultState) { + e.RLock() + defer e.RUnlock() + + if !e.full && e.idx == 0 { + return nil, 0, bufferEmpty + } + + if e.full { + if count > e.capacity { + count = e.capacity + } + if count > e.idx { + startPos := e.capacity - count + e.idx + r1 := &eventRange{ + start: startPos, + end: e.capacity, + } + r2 := &eventRange{ + start: 0, + end: e.idx, + } + + return e.getEntriesFromRanges(r1, r2), e.pos2id(startPos), resultOK + } + + startIdx := e.idx - count + return e.getEntriesFromRanges(&eventRange{ + start: startIdx, + end: e.idx, + }, nil), e.pos2id(startIdx), resultOK + } + + if count > e.idx { + count = e.idx + } + startIdx := e.idx - count + return e.getEntriesFromRanges(&eventRange{ + start: startIdx, + end: e.idx, + }, nil), startIdx, resultOK +} + +func (e *eventRingBuffer) getEntriesFromRanges(r1, r2 *eventRange) []*si.EventRecord { + var total uint64 + var src []*si.EventRecord + if r2 == nil { + total = r1.end - r1.start + src = e.events[r1.start:r1.end] + } else { + total = (r1.end - r1.start) + (r2.end - r2.start) + src = e.events[r1.start:r1.end] + src = append(src, e.events[r2.start:r2.end]...) Review Comment: The re-slice points to the same underlying storage. When append is called a new array must be allocated so this does the same thing as before. The sharing of the underlying storage is used in the 2nd copy with the re-slice. When we have two ranges the fist will be the end of the buffer, the second the start, this is true always. So this will work, with least allocation overhead. No check needed for r2 being nil as that is already handled: ``` total := (r1.end - r1.start) + (r2.end - r2.start) dest := make([]*si.EventRecord, total) // all the way to the end of the src, r1.end should be same as len(src) copy(dest, src[r1.start:]) copyNext := r1.end - r1.start // dest limits what can be copied from src copy(dest[copyNext:], src[r2.start:]) return dest ``` ########## pkg/events/event_ringbuffer.go: ########## @@ -0,0 +1,213 @@ +/* + 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 ( + "sync" + + "github.com/apache/yunikorn-scheduler-interface/lib/go/si" +) + +type resultState int + +const ( + resultOK resultState = iota + bufferEmpty + idNotFound +) + +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. +// +// Retrieving the records can be achieved with GetEventsFromID and GetRecentEntries. +type eventRingBuffer struct { + events []*si.EventRecord + capacity uint64 + idx uint64 + full bool + + id uint64 // increasing unique id + startId uint64 // id of the message at index 0 + lowestId uint64 // the lowest available id in the buffer (pointed at by e.idx when full) + + sync.RWMutex +} + +// Add adds an event to the ring buffer. If the buffer is full, the oldest element is overwritten. +// This method never fails. +// Each event has an ID, however, this mapping is not stored directly. Instead, we store the starting ID at +// index 0 and the lowest available ID. +func (e *eventRingBuffer) Add(event *si.EventRecord) { + e.Lock() + defer e.Unlock() + + e.events[e.idx] = event + if e.idx == 0 { + e.startId = e.id + } + if e.idx == e.capacity-1 { + e.full = true + } + e.idx = (e.idx + 1) % e.capacity + if e.full { + // once the buffer becomes full, we keep incrementing this value + // this is the id of the element which is about to be overwritten in the next Add() call + e.lowestId++ + } + + e.id++ +} + +func (e *eventRingBuffer) GetEventsFromID(id uint64) ([]*si.EventRecord, resultState) { + e.RLock() + defer e.RUnlock() + + storedId, state := e.id2pos(id) + if state != resultOK { + return nil, state + } + + if e.full { + r1 := &eventRange{ + start: storedId, + end: e.capacity, + } + r2 := &eventRange{ + start: 0, + end: e.idx, + } + return e.getEntriesFromRanges(r1, r2), resultOK + } + + return e.getEntriesFromRanges(&eventRange{ + start: storedId, + end: e.idx, + }, nil), resultOK +} + +func (e *eventRingBuffer) GetRecentEntries(count uint64) ([]*si.EventRecord, uint64, resultState) { + e.RLock() + defer e.RUnlock() + + if !e.full && e.idx == 0 { + return nil, 0, bufferEmpty + } + + if e.full { + if count > e.capacity { + count = e.capacity + } + if count > e.idx { + startPos := e.capacity - count + e.idx + r1 := &eventRange{ + start: startPos, + end: e.capacity, + } + r2 := &eventRange{ + start: 0, + end: e.idx, + } + + return e.getEntriesFromRanges(r1, r2), e.pos2id(startPos), resultOK + } + + startIdx := e.idx - count + return e.getEntriesFromRanges(&eventRange{ + start: startIdx, + end: e.idx, + }, nil), e.pos2id(startIdx), resultOK + } + + if count > e.idx { + count = e.idx + } + startIdx := e.idx - count + return e.getEntriesFromRanges(&eventRange{ + start: startIdx, + end: e.idx, + }, nil), startIdx, resultOK +} + +func (e *eventRingBuffer) getEntriesFromRanges(r1, r2 *eventRange) []*si.EventRecord { + var total uint64 + var src []*si.EventRecord + if r2 == nil { + total = r1.end - r1.start + src = e.events[r1.start:r1.end] Review Comment: No need for a re-slice, this can be a simple one step: ``` if r2 == nil { dest := make([]*si.EventRecord, r1.end - r1.start) // dest limits what can be copied from src copy(dest, src[r1.start:]) return dest } ``` -- This is an automated message from the Apache Git Service. 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