[GitHub] [yunikorn-core] pbacsko commented on a diff in pull request #533: [WIP] [YUNIKORN-1709] Store events separately for event streaming

["pbacsko (via GitHub)" <gi...@apache.org>]

pbacsko commented on code in PR #533:
URL: https://github.com/apache/yunikorn-core/pull/533#discussion_r1181641754


##########
pkg/events/event_ringbuffer.go:
##########
@@ -0,0 +1,175 @@
+/*
+ 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 (
+	"time"
+
+	"github.com/apache/yunikorn-scheduler-interface/lib/go/si"
+)
+
+const latestUnset int64 = -1 << 63
+
+var now = time.Now
+
+// EventRingBuffer A specialized circular buffer to store event objects.
+//
+// Unlike to regular circular buffers, new entries can be added if the buffer is full. In this case,
+// the oldest entry is overwritten. This is not a classic enqueue operation, so it's named differently.
+//
+// Retrieving the records can be achieved with GetLatestEntriesCount and GetLatestEntries. Since these do not
+// remove the elements, they are not regular dequeue operations either.
+//
+// Entries have a maximum lifespan defined in nanoseconds. Cleanup of expired objects occurs when a call to
+// RemoveExpiredEntries is made.
+//
+// The buffer does not use locking, proper synchronization is delegated to the client.
+type EventRingBuffer struct {
+	events        []*si.EventRecord

Review Comment:
   IMO we need to switch to `[]si.EventRecord` if we want to store a lot of elements. We want to avoid GC interactions, so using a value type here is very much reasonable.
   
   In fact, I'm considering a specia, internal type here instead of `EventRecord` with interned strings. There will be a lot of string duplications in the events (especially IDs). 
   This library looks promising: https://github.com/philpearl/intern



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