# Question about fd8: Fetch multiple messages from disk **URL:** \ **Category:** Challenges\ **Tags:** challenge:kafka\ **Created:** [June 9, 2025, 3:56pm UTC](https://forum.codecrafters.io/t/question-about-fd8-fetch-multiple-messages-from-disk/11897 "2025-06-09T15:56:52Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![chuanhd](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/chuanhd/32/7582_2.png) [@chuanhd](https://forum.codecrafters.io/u/chuanhd)\ **Post date:** [June 9, 2025, 3:56pm UTC](https://forum.codecrafters.io/t/question-about-fd8-fetch-multiple-messages-from-disk/11897/1 "2025-06-09T15:56:52Z")
Hi everyone, I hope you’re all doing well. I’m working on the FD8 challenge and I’ve run into an issue where the tester doesn’t seem to read the next `RecordBatch` data in the response. This results in the error: `Unexpected xx bytes remaining in decoder`. I reviewed the tester code in [this file](https://github.com/codecrafters-io/kafka-tester/blob/586d4ddb28f593bc696f384c8bcece681d6b949c/protocol/api/fetch_response.go#L254), and it looks like I may have more than 10 extra bytes after reading the first `RecordBatch`. Does anyone have any insights on why this might be happening? Thanks in advance for any help! ```auto [tester::#FD8] Hexdump of received "Fetch" response: [tester::#FD8] Idx | Hex | ASCII [tester::#FD8] -----+-------------------------------------------------+----------------- [tester::#FD8] 0000 | 00 00 00 ef 4b 02 ba 39 00 00 00 00 00 00 00 00 | ....K..9........ [tester::#FD8] 0010 | 00 00 00 02 00 00 00 00 00 00 40 00 80 00 00 00 | ..........@..... [tester::#FD8] 0020 | 00 00 00 59 02 00 00 00 00 00 00 00 00 00 00 00 | ...Y............ [tester::#FD8] 0030 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................ [tester::#FD8] 0040 | 00 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 | ................ [tester::#FD8] 0050 | 00 00 00 00 44 00 00 00 00 02 ab fd 04 91 00 00 | ....D........... [tester::#FD8] 0060 | 00 00 00 00 00 00 01 91 e0 5b 6d 8b 00 00 01 91 | .........[m..... [tester::#FD8] 0070 | e0 5b 6d 8b 00 00 00 00 00 00 00 00 00 00 00 00 | .[m............. [tester::#FD8] 0080 | 00 00 00 00 00 01 24 00 00 00 01 18 48 65 6c 6c | ......$.....Hell [tester::#FD8] 0090 | 6f 20 4b 61 66 6b 61 21 00 00 00 00 00 00 00 00 | o Kafka!........ [tester::#FD8] 00a0 | 01 00 00 00 4b 00 00 00 00 02 55 60 53 93 00 00 | ....K.....U`S... [tester::#FD8] 00b0 | 00 00 00 00 00 00 01 91 e0 5b 6d 8b 00 00 01 91 | .........[m..... [tester::#FD8] 00c0 | e0 5b 6d 8b 00 00 00 00 00 00 00 00 00 00 00 00 | .[m............. [tester::#FD8] 00d0 | 00 00 00 00 00 01 32 00 00 00 01 26 48 65 6c 6c | ......2....&Hell [tester::#FD8] 00e0 | 6f 20 43 6f 64 65 43 72 61 66 74 65 72 73 21 00 | o CodeCrafters!. [tester::#FD8] 00f0 | 00 00 00 | ... [tester::#FD8] [tester::#FD8] [Decoder] - .ResponseHeader [tester::#FD8] [Decoder] - .correlation_id (1258469945) [tester::#FD8] [Decoder] - .TAG_BUFFER [tester::#FD8] [Decoder] - .ResponseBody [tester::#FD8] [Decoder] - .throttle_time_ms (0) [tester::#FD8] [Decoder] - .error_code (0) [tester::#FD8] [Decoder] - .session_id (0) [tester::#FD8] [Decoder] - .num_responses (1) [tester::#FD8] [Decoder] - .TopicResponse[0] [tester::#FD8] [Decoder] - .topic_id (00000000-0000-4000-8000-000000000059) [tester::#FD8] [Decoder] - .num_partitions (1) [tester::#FD8] [Decoder] - .PartitionResponse[0] [tester::#FD8] [Decoder] - .partition_index (0) [tester::#FD8] [Decoder] - .error_code (0) [tester::#FD8] [Decoder] - .high_watermark (0) [tester::#FD8] [Decoder] - .last_stable_offset (0) [tester::#FD8] [Decoder] - .log_start_offset (0) [tester::#FD8] [Decoder] - .num_aborted_transactions (0) [tester::#FD8] [Decoder] - .preferred_read_replica (0) [tester::#FD8] [Decoder] - .compact_records_length (2) [tester::#FD8] [Decoder] - .RecordBatch[0] [tester::#FD8] [Decoder] - .base_offset (0) [tester::#FD8] [Decoder] - .batch_length (68) [tester::#FD8] [Decoder] - .partition_leader_epoch (0) [tester::#FD8] [Decoder] - .magic_byte (2) [tester::#FD8] [Decoder] - .crc (-1409481583) [tester::#FD8] [Decoder] - .record_attributes (0) [tester::#FD8] [Decoder] - .last_offset_delta (0) [tester::#FD8] [Decoder] - .base_timestamp (1726045973899) [tester::#FD8] [Decoder] - .max_timestamp (1726045973899) [tester::#FD8] [Decoder] - .producer_id (0) [tester::#FD8] [Decoder] - .producer_epoch (0) [tester::#FD8] [Decoder] - .base_sequence (0) [tester::#FD8] [Decoder] - .num_records (1) [tester::#FD8] [Decoder] - .Record[0] [tester::#FD8] [Decoder] - .length (18) [tester::#FD8] [Decoder] - .attributes (0) [tester::#FD8] [Decoder] - .timestamp_delta (0) [tester::#FD8] [Decoder] - .offset_delta (0) [tester::#FD8] [Decoder] - .key_length (-1) [tester::#FD8] [Decoder] - .key ("") [tester::#FD8] [Decoder] - .value_length (12) [tester::#FD8] [Decoder] - .value ("Hello Kafka!") [tester::#FD8] [Decoder] - .num_headers (0) [tester::#FD8] [Decoder] - .TAG_BUFFER [tester::#FD8] [Decoder] - .TAG_BUFFER [tester::#FD8] [Decoder] - .TAG_BUFFER [tester::#FD8] Received: [tester::#FD8] Hex (bytes 147-162) | ASCII [tester::#FD8] ------------------------------------------------+------------------ [tester::#FD8] 21 00 00 00 00 00 00 00 00 01 00 00 00 4b 00 00 | !............K.. [tester::#FD8] ^ ^ [tester::#FD8] Error: unexpected 87 bytes remaining in decoder after decoding FetchResponse [tester::#FD8] Context: [tester::#FD8] - Fetch Response v16 [tester::#FD8] - Response Body [tester::#FD8] [tester::#FD8] Test failed [tester::#FD8] Terminating program ``` ---
**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\ **Post date:** [June 9, 2025, 5:28pm UTC](https://forum.codecrafters.io/t/question-about-fd8-fetch-multiple-messages-from-disk/11897/3 "2025-06-09T17:28:15Z")
Hey @chuanhd, `compact_records_length` is incorrect: ![image](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/2X/3/3efc540b9ee7b544032ad7eac5a3b11c161a6ae2.png) Please note that RecordBatch is of type `COMPACT_RECORDS`: ![image](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/2X/d/d0a079441fc5d9f5f19a38cf1a6505449f48b107.png) ![image](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/2X/b/ba45c67877efe4fcd0cf4004e9c2f9c2b4199c3e.png) Let me know if you’d like further clarification! ---
**Author:** ![chuanhd](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/chuanhd/32/7582_2.png) [@chuanhd](https://forum.codecrafters.io/u/chuanhd)\ **Post date:** [June 10, 2025, 7:16am UTC](https://forum.codecrafters.io/t/question-about-fd8-fetch-multiple-messages-from-disk/11897/4 "2025-06-10T07:16:00Z")
Oh, I see. Problem solved. Thank you very much! ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/3X/7/0/700657133935c15703e22c7c8870394f6e6dc27d.svg) [@system](https://forum.codecrafters.io/u/system)\ **Post date:** [June 15, 2025, 7:16am UTC](https://forum.codecrafters.io/t/question-about-fd8-fetch-multiple-messages-from-disk/11897/5 "2025-06-15T07:16:13Z")
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