[FLINK-12044] Flink CEP discards events as late if they have timestamps <= 0

• Type: Bug
• Status: Reopened
• Priority: Not a Priority
• Resolution: Unresolved
• Affects Version/s: 1.7.2
• Component/s: Library / CEP
• Assignee: Unassigned
• Reporter: Arseniy Tashoyan
• Created: 28/Mar/19 08:31
• Updated: 29/Jul/21 07:36

Description

Let's make an input stream like this:

env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
val events = env.fromElements(
      Event(timestamp = 0L, siteId),
      Event(timestamp = 500L, siteId)
)
.assignTimestampsAndWatermarks(new BoundedOutOfOrdernessTimestampExtractor{...})

For this stream the event with timestamp = 0L will be treated as late. The reason is AbstractKeyedCEPPatternOperator that initializes lastWatermark with the default value provided by the compiler: zero. Would it be more correct to initialize lastWatermark with Long.MIN_VALUE?

Of course, this is not a blocking defect, but I had really hard times to find why my unit test disregards the first event. Strictly speaking, this behavior seems incorrect.