Greptile Overview

Greptile Summary

This PR fixes event deduplication to work across flush cycles by implementing time-based hash cleanup with a 60-second window.

Key Changes:

• Changed payloadHashes from Set<string> to Map<string, number> to track timestamps
• Improved timestamp precision from minute-level to second-level in hash generation
• Removed payloadHashes.clear() from flush() to maintain deduplication across flush cycles
• Added automatic cleanup of hashes older than 60 seconds in isDuplicate()

What This Fixes:
Previously, duplicate events could be sent if they occurred across different flush cycles (which happen every 10-30 seconds or when 20 events are queued). The hash set was cleared on every flush, breaking deduplication. Now, events with identical content within a 60-second window are properly deduplicated regardless of flush cycles.

Issues Found:

• Critical: Timing inconsistency between generateMessageId() (uses event.original_timestamp) and isDuplicate() (uses Date.now()). If events have past/future timestamps, deduplication window won't work correctly.
• Minor: Unused import toDateHourMinute should be removed
• Test Quality: Tests lack proper assertions to verify deduplication behavior

Documentation:
Excellent documentation added with multiple guides explaining the fix, debugging steps, and visual diagrams.

Confidence Score: 3/5

• This PR has a critical timing inconsistency that could cause the deduplication to fail in production scenarios
• The core deduplication logic has a significant issue: generateMessageId() formats timestamps from event.original_timestamp for hashing, while isDuplicate() uses Date.now() for the time window. This mismatch means events with past/future original_timestamp values won't be deduplicated correctly. The 60s window is measured from the current system time, but the hash is based on the event's timestamp, creating an inconsistency. Additionally, tests don't verify actual deduplication behavior (no assertions on queue state or logger calls).
• src/lib/queue/EventQueue.ts requires attention to fix the timing inconsistency between hash generation and duplicate detection. test/lib/queue/EventQueue.spec.ts needs better assertions to actually verify deduplication works.

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant App as Application
    participant EQ as EventQueue
    participant Hash as payloadHashes Map
    participant API as Analytics API

    Note over App,API: Event Submission Flow with Deduplication

    App->>EQ: enqueue(event1, timestamp: 10:30:15)
    EQ->>EQ: generateMessageId(event1)
    Note over EQ: Format timestamp to second precision<br/>(2025-01-01 10:30:15)
    EQ->>EQ: hash(event + formatted timestamp)
    EQ->>EQ: isDuplicate(hash_abc)
    EQ->>Hash: Clean up hashes > 60s old
    EQ->>Hash: has(hash_abc)?
    Hash-->>EQ: false
    EQ->>Hash: set(hash_abc, now=10:30:15)
    EQ->>EQ: queue.push(event1)
    Note over EQ: Queue size: 1

    Note over EQ: ... 10 seconds later ...

    App->>EQ: enqueue(event2, timestamp: 10:30:25)<br/>(same content as event1)
    EQ->>EQ: generateMessageId(event2)
    EQ->>EQ: hash(event + formatted timestamp)
    EQ->>EQ: isDuplicate(hash_abc)
    EQ->>Hash: Clean up hashes > 60s old
    Note over Hash: No hashes to clean (all < 60s)
    EQ->>Hash: has(hash_abc)?
    Hash-->>EQ: true (stored at 10:30:15)
    Note over EQ: Duplicate detected!<br/>Time since last: 10s
    EQ->>EQ: logger.warn("Duplicate blocked, sent 10s ago")
    EQ-->>App: return (blocked)

    Note over EQ: ... Queue reaches 20 events ...

    EQ->>EQ: flush()
    Note over EQ,Hash: Hash map NOT cleared<br/>(preserves deduplication)
    EQ->>API: POST /events (batch)
    API-->>EQ: 200 OK

    Note over EQ: ... 50 seconds after event1 ...

    App->>EQ: enqueue(event3, timestamp: 10:31:05)<br/>(same content as event1)
    EQ->>EQ: generateMessageId(event3)
    EQ->>EQ: isDuplicate(hash_abc)
    EQ->>Hash: Clean up hashes > 60s old
    Note over Hash: hash_abc is 50s old, keep it
    EQ->>Hash: has(hash_abc)?
    Hash-->>EQ: true
    EQ->>EQ: logger.warn("Duplicate blocked, sent 50s ago")
    EQ-->>App: return (blocked)

    Note over EQ: ... 70 seconds after event1 ...

    App->>EQ: enqueue(event4, timestamp: 10:31:25)<br/>(same content as event1)
    EQ->>EQ: generateMessageId(event4)
    EQ->>EQ: isDuplicate(hash_abc)
    EQ->>Hash: Clean up hashes > 60s old
    Note over Hash: hash_abc is 70s old, DELETE
    EQ->>Hash: delete(hash_abc)
    EQ->>Hash: has(hash_abc)?
    Hash-->>EQ: false
    EQ->>Hash: set(hash_abc, now=10:31:25)
    EQ->>EQ: queue.push(event4)
    Note over EQ: Allowed (outside 60s window)

_{7 files reviewed, 3 comments}

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Greptile Overview

Greptile Summary

This PR fixes event deduplication by switching from minute-level to second-level timestamp precision and maintaining hashes across flush cycles. The implementation now uses a consistent 60-second window and removes the problematic payloadHashes.clear() on flush.

Key improvements:

• Changed generateMessageId() to return both hash and event timestamp for consistent time-based comparisons
• Updated isDuplicate() to use event timestamps instead of Date.now(), fixing timing inconsistencies
• Hash map now persists across flush cycles with automatic cleanup of entries older than 60 seconds
• Comprehensive test suite added with proper assertions using sinon stubs

Critical issue found:

• The cleanup logic in isDuplicate() (lines 268-276) has a bug when events arrive out-of-order. It uses the current event's timestamp to determine which hashes to delete, which can incorrectly remove valid hashes when an older event arrives after a newer one. The cleanup should use a monotonically increasing timestamp reference rather than the current event's timestamp.

Confidence Score: 2/5

• This PR contains a critical logic bug in the cleanup mechanism that could cause incorrect behavior with out-of-order events
• While the PR significantly improves the deduplication system by fixing the timing inconsistency and adding comprehensive tests, there is a critical bug in the cleanup logic (lines 268-276) that uses the current event's timestamp to delete old hashes. This will fail when events arrive out-of-order, potentially deleting hashes that are still within the deduplication window from the perspective of later events. The tests don't cover this scenario.
• Pay close attention to src/lib/queue/EventQueue.ts - the isDuplicate() method's cleanup logic needs to be fixed to handle out-of-order events correctly

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant Client
    participant EventQueue
    participant generateMessageId
    participant isDuplicate
    participant payloadHashes
    participant APIServer

    Client->>EventQueue: enqueue(event)
    EventQueue->>generateMessageId: generateMessageId(event)
    Note over generateMessageId: Extract event.original_timestamp
    Note over generateMessageId: Format to second precision<br/>(YYYY-MM-DD HH:mm:ss)
    Note over generateMessageId: Hash event with formatted timestamp
    generateMessageId-->>EventQueue: { hash, timestamp }
    
    EventQueue->>isDuplicate: isDuplicate(hash, timestamp)
    
    Note over isDuplicate: Cleanup Phase
    loop For each stored hash
        isDuplicate->>payloadHashes: Get stored timestamp
        alt timestamp - stored > 60s
            isDuplicate->>payloadHashes: Delete old hash
        end
    end
    
    Note over isDuplicate: Duplicate Check
    isDuplicate->>payloadHashes: Check if hash exists
    alt Hash exists
        Note over isDuplicate: Calculate time since last event
        isDuplicate-->>EventQueue: true (duplicate)
        EventQueue-->>Client: return (event blocked)
    else Hash does not exist
        isDuplicate->>payloadHashes: Store hash with timestamp
        isDuplicate-->>EventQueue: false (not duplicate)
        EventQueue->>EventQueue: Add to queue
        
        alt Queue reaches flushAt or maxQueueSize
            EventQueue->>APIServer: flush() - POST events
            Note over EventQueue: payloadHashes NOT cleared<br/>(maintains deduplication)
            APIServer-->>EventQueue: Success
        end
        
        EventQueue-->>Client: Event enqueued
    end

_{3 files reviewed, 1 comment}

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Greptile Overview

Greptile Summary

Refactored event deduplication to use a timestamped hash map with a 60-second real-time window, fixing three critical issues: hash clearing on flush (breaking cross-flush deduplication), timing inconsistency between hash generation and cleanup, and incorrect cleanup with out-of-order events. The solution now properly maintains deduplication state across flush cycles by storing hashes with Date.now() timestamps and cleaning them based on real elapsed time rather than event timestamps.

Key Changes:

• Changed payloadHashes from Set<string> to Map<string, number> mapping hash to Date.now() timestamp
• Removed payloadHashes.clear() from flush() method to maintain deduplication across flush cycles
• Updated isDuplicate() to clean up old hashes based on real-time window (Date.now() - stored > 60s)
• Enhanced hash generation to use second-level precision while returning both hash and timestamp
• Added comprehensive test suite covering same-second duplicates, cross-flush behavior, out-of-order events, and real-world scenarios

Issues Found:

• 8 documentation markdown files should be removed (development notes, not production docs)
• Tests only verify logger calls, not actual queue state
• Missing test for deduplication window expiration (events allowed after 60s)
• Unused timestamp return value from generateMessageId()
• Cleanup logic uses temporary array instead of direct deletion

Confidence Score: 4/5

• This PR is safe to merge with minor cleanup - the core deduplication logic is sound and fixes critical bugs
• Score reflects solid implementation of deduplication fix that addresses real production issues (cross-flush deduplication, out-of-order events). However, the PR includes 8 documentation files that should be removed, tests could be more thorough (missing window expiration test, only checking logger calls), and there are minor code quality improvements possible. The core logic is correct and the fix is important, but cleanup is recommended before merge.
• Remove all 8 documentation .md files (FINAL_FIX_SUMMARY.md, OUT_OF_ORDER_FIX.md, etc.) before merging. Test file should add assertions on queue state and window expiration behavior.

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant Client
    participant EventQueue
    participant isDuplicate
    participant payloadHashes as Map<hash,timestamp>
    participant Queue as queue[]
    
    Client->>EventQueue: enqueue(event1, timestamp: 10:30:15.123Z)
    EventQueue->>EventQueue: generateMessageId(event1)
    Note over EventQueue: Hash includes timestamp<br/>rounded to seconds:<br/>"2025-01-01 10:30:15"
    EventQueue->>EventQueue: hash = "abc123..."
    EventQueue->>isDuplicate: isDuplicate("abc123")
    isDuplicate->>isDuplicate: now = Date.now() = T0
    isDuplicate->>payloadHashes: Clean up old hashes<br/>(now - stored > 60s)
    isDuplicate->>payloadHashes: has("abc123")?
    payloadHashes-->>isDuplicate: false
    isDuplicate->>payloadHashes: set("abc123", T0)
    isDuplicate-->>EventQueue: false (not duplicate)
    EventQueue->>Queue: push(event1)
    EventQueue-->>Client: Event enqueued
    
    Client->>EventQueue: enqueue(event2, timestamp: 10:30:15.456Z)
    Note over Client: Same second, different ms<br/>Same event data
    EventQueue->>EventQueue: generateMessageId(event2)
    Note over EventQueue: Hash rounds to same second:<br/>"2025-01-01 10:30:15"
    EventQueue->>EventQueue: hash = "abc123..." (SAME!)
    EventQueue->>isDuplicate: isDuplicate("abc123")
    isDuplicate->>isDuplicate: now = Date.now() = T0 + 0.3s
    isDuplicate->>payloadHashes: Clean up old hashes
    isDuplicate->>payloadHashes: has("abc123")?
    payloadHashes-->>isDuplicate: true (stored at T0)
    isDuplicate->>isDuplicate: elapsed = (T0+0.3s) - T0 = 0.3s
    isDuplicate-->>EventQueue: true (DUPLICATE)
    EventQueue->>EventQueue: logger.warn("Duplicate detected")
    EventQueue-->>Client: Event blocked
    
    Note over EventQueue: Queue reaches flushAt=20
    EventQueue->>EventQueue: flush()
    Note over EventQueue: payloadHashes NOT cleared<br/>(preserves dedup state)
    EventQueue->>EventQueue: Send batch to API
    
    Client->>EventQueue: enqueue(event3, timestamp: 10:30:15.789Z)
    Note over Client: After flush, same second
    EventQueue->>isDuplicate: isDuplicate("abc123")
    isDuplicate->>payloadHashes: has("abc123")?
    payloadHashes-->>isDuplicate: true (still in memory)
    isDuplicate-->>EventQueue: true (DUPLICATE)
    EventQueue-->>Client: Event blocked (cross-flush dedup works!)

_{4 files reviewed, 5 comments}

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Greptile Overview

Greptile Summary

Improves client-side event deduplication by switching from minute-precision to second-precision hashing and implementing a 60-second real-time deduplication window that persists across flush cycles.

Key Changes:

• Second-precision hashing: Events within the same second (ignoring milliseconds) are considered duplicates, preventing rapid duplicate submissions
• Real-time window tracking: Uses Date.now() to store hash timestamps instead of event timestamps, fixing the out-of-order event handling issue noted in previous comments
• Cross-flush persistence: Removed payloadHashes.clear() on flush, maintaining deduplication state across batch sends
• Automatic cleanup: Old hashes (>60s) are cleaned up during each isDuplicate() check
• Comprehensive tests: 13 test cases covering basic deduplication, time windows, cross-flush behavior, cleanup logic, and real-world scenarios including window expiration

Previous Issues Addressed:

• ✅ Out-of-order cleanup logic fixed (src/lib/queue/EventQueue.ts:268-280)
• ✅ Tests now include queue length assertions (test/lib/queue/EventQueue.spec.ts:88, 99)
• ✅ Window expiration properly tested with Date.now() mocking (test/lib/queue/EventQueue.spec.ts:274-312)
• ⚠️ Documentation files mentioned in PR description are not in changeset (expected behavior)

Minor Issue:

• Unused import toDateHourMinute should be removed (src/lib/queue/EventQueue.ts:8)

Confidence Score: 4/5

• Safe to merge with one minor cleanup (unused import)
• Implementation correctly addresses the out-of-order event handling issue from previous review. Comprehensive test suite with proper Date.now() mocking validates the 60s window behavior. Only issue is a cosmetic unused import.
• src/lib/queue/EventQueue.ts requires minor cleanup (remove unused import on line 8), otherwise no files require special attention

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant Client
    participant EventQueue
    participant PayloadHashes as PayloadHashes<br/>Map<hash, timestamp>
    participant Logger
    participant API
    
    Client->>EventQueue: enqueue(event)
    EventQueue->>EventQueue: generateMessageId(event)
    Note over EventQueue: Hash = hash(event + timestamp<br/>formatted to second precision)
    
    EventQueue->>EventQueue: isDuplicate(hash)
    EventQueue->>PayloadHashes: Check for old hashes
    Note over PayloadHashes: Cleanup: Delete hashes where<br/>Date.now() - storedTimestamp > 60s
    
    alt Hash exists in Map
        PayloadHashes-->>EventQueue: Hash found
        EventQueue->>Logger: warn("Duplicate detected...")
        EventQueue-->>Client: Return (blocked)
    else Hash not found
        PayloadHashes-->>EventQueue: Hash not found
        EventQueue->>PayloadHashes: set(hash, Date.now())
        EventQueue->>EventQueue: queue.push(event)
        EventQueue->>Logger: log("Event enqueued")
        
        alt Queue reaches flushAt (20 events)
            EventQueue->>EventQueue: flush()
            EventQueue->>API: POST /events (batch)
            Note over EventQueue,PayloadHashes: payloadHashes NOT cleared<br/>Maintains deduplication across flushes
            API-->>EventQueue: 200 OK
        end
        
        EventQueue-->>Client: Success
    end

_{10 files reviewed, 1 comment}

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Greptile Overview

Greptile Summary

This PR overhauls the event deduplication system to fix critical bugs that allowed duplicate events to be sent. The implementation now uses a Map-based approach with Date.now() for time-based cleanup, ensuring robust deduplication across flush cycles.

Key improvements:

• Replaced Set with Map<string, number> to track when hashes were first seen
• Changed hash precision from minute-level to second-level for better granularity
• Removed payloadHashes.clear() from flush() to maintain deduplication across flush cycles
• Implemented real-time cleanup using Date.now() instead of event timestamps, correctly handling out-of-order events
• Added comprehensive test suite with proper assertions on queue length and logger calls
• Updated deduplication window to 60 seconds of real elapsed time

The fix addresses three critical issues: hash clearing on flush, timing inconsistency between hash generation and window checking, and incorrect cleanup with out-of-order events.

Confidence Score: 5/5

• This PR is safe to merge with high confidence
• The implementation correctly fixes the deduplication logic with proper separation of concerns (hash generation, duplicate detection, and cleanup). The use of Date.now() for cleanup elegantly handles out-of-order events. Comprehensive test coverage includes window expiration tests with Date.now() mocking, cross-flush persistence verification, and real-world scenarios. The logic is sound and all edge cases are handled properly.
• No files require special attention. Consider removing DEDUPLICATION_FIX_SUMMARY.md as it's development documentation rather than production code documentation.

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant Client
    participant EventQueue
    participant PayloadHashes as Map<hash, timestamp>
    participant Logger
    participant API

    Note over Client,API: Event Enqueueing & Deduplication Flow

    Client->>EventQueue: enqueue(event)
    EventQueue->>EventQueue: generateMessageId(event)
    Note over EventQueue: Hash = f(event data + timestamp)<br/>Rounded to second precision
    EventQueue-->>EventQueue: message_id (hash)
    
    EventQueue->>EventQueue: isDuplicate(message_id)
    Note over EventQueue: now = Date.now()
    
    EventQueue->>PayloadHashes: forEach(storedTimestamp, hash)
    Note over PayloadHashes: Cleanup: Remove hashes where<br/>now - storedTimestamp > 60s
    
    alt Hash exists in map
        PayloadHashes-->>EventQueue: true (found)
        EventQueue->>Logger: warn("Duplicate detected")
        EventQueue-->>Client: return (blocked)
    else Hash not in map
        PayloadHashes-->>EventQueue: false (not found)
        EventQueue->>PayloadHashes: set(message_id, now)
        EventQueue->>EventQueue: queue.push(event)
        EventQueue->>Logger: log("Event enqueued")
        
        alt Queue reaches flushAt threshold
            EventQueue->>EventQueue: flush()
            Note over EventQueue: Note: payloadHashes NOT cleared<br/>Hashes persist across flushes
            EventQueue->>API: POST /events (batch)
            API-->>EventQueue: 200 OK
        end
        
        EventQueue-->>Client: return (success)
    end

    Note over PayloadHashes: Deduplication Window: 60s<br/>Based on real time (Date.now())<br/>Not event timestamps

_{5 files reviewed, 2 comments}

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Greptile Overview

Greptile Summary

This PR implements a robust event deduplication mechanism that prevents duplicate analytics events from being sent within a 60-second real-time window. The fix addresses four critical bugs: hash clearing on flush, inconsistent time sources for deduplication vs cleanup, incorrect out-of-order event handling, and memory leaks from missing periodic cleanup.

Key improvements:

• Changed from Set<string> to Map<string, number> to track when each event hash was first seen (using Date.now())
• Removed payloadHashes.clear() on flush, enabling cross-flush deduplication
• Extracted cleanup logic to separate cleanupOldHashes() method that uses real elapsed time (Date.now()) consistently
• Added periodic cleanup during flush cycles to prevent memory leaks even when events stop arriving
• Improved hash precision from minute-level to second-level for better granularity
• Added comprehensive test suite with proper queue state assertions and time-mocking

Technical correctness:
The implementation correctly handles the separation of concerns: hash generation (event identity), deduplication (duplicate detection), and cleanup (memory management). The use of Date.now() for both storage and cleanup timestamps ensures consistent behavior regardless of event timestamp ordering.

Minor optimization note:
The cleanupOldHashes() method creates a temporary array of hashes to delete (line 274-281) to avoid modifying the Map during iteration. While JavaScript Maps support safe deletion during forEach iteration, this conservative approach is acceptable given cleanup runs infrequently (every flush cycle).

Confidence Score: 4/5

• This PR is safe to merge with minimal risk - the deduplication logic is sound and well-tested
• Score reflects solid implementation with comprehensive tests and correct handling of edge cases. Not a 5 due to: (1) the included 381-line documentation file that should be in PR description instead, and (2) minor cleanup inefficiency using temporary array. The core deduplication logic is correct and addresses real bugs.
• Consider removing DEDUPLICATION_FIX_SUMMARY.md from the repository - detailed implementation notes like this are better suited for PR descriptions or internal documentation

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant User
    participant SDK
    participant EventQueue
    participant HashMap as payloadHashes<br/>Map<hash, timestamp>
    participant Server

    Note over EventQueue: Deduplication Window = 60s

    User->>SDK: track("transaction_submit")
    SDK->>EventQueue: enqueue(event)
    
    EventQueue->>EventQueue: generateMessageId(event)
    Note over EventQueue: Hash = SHA256(event data + <br/>timestamp to second precision)
    
    EventQueue->>EventQueue: isDuplicate(hash)?
    EventQueue->>HashMap: cleanupOldHashes()
    Note over HashMap: Remove hashes where<br/>Date.now() - stored > 60s
    
    EventQueue->>HashMap: has(hash)?
    HashMap-->>EventQueue: false (new event)
    
    EventQueue->>HashMap: set(hash, Date.now())
    EventQueue->>EventQueue: queue.push(event)
    Note over EventQueue: Event queued successfully
    
    User->>SDK: track("transaction_submit")<br/>(duplicate, 5s later)
    SDK->>EventQueue: enqueue(event)
    EventQueue->>EventQueue: generateMessageId(event)
    Note over EventQueue: Same hash generated
    EventQueue->>EventQueue: isDuplicate(hash)?
    EventQueue->>HashMap: has(hash)?
    HashMap-->>EventQueue: true (seen 5s ago)
    EventQueue->>EventQueue: log warning & block
    Note over EventQueue: Duplicate blocked ✓
    
    Note over EventQueue: Flush triggered<br/>(queue full or interval)
    EventQueue->>EventQueue: flush()
    EventQueue->>HashMap: cleanupOldHashes()
    EventQueue->>Server: POST /events (batch)
    Server-->>EventQueue: 200 OK
    Note over HashMap: Hash NOT cleared<br/>Cross-flush persistence ✓
    
    Note over EventQueue: 61 seconds pass...
    EventQueue->>HashMap: cleanupOldHashes()
    Note over HashMap: Hash expired & removed
    
    User->>SDK: track("transaction_submit")<br/>(same event, after 60s)
    SDK->>EventQueue: enqueue(event)
    EventQueue->>EventQueue: isDuplicate(hash)?
    EventQueue->>HashMap: has(hash)?
    HashMap-->>EventQueue: false (expired)
    EventQueue->>HashMap: set(hash, Date.now())
    EventQueue->>EventQueue: queue.push(event)
    Note over EventQueue: Allowed after window ✓

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