bug: Incorrectly showing stale block as part of the main chain

[0xB10C]

For block 881780, the SecPool block is shown to be in the main chain on fork-observer. However, the Foundry USA block is in the main chain and the SecPool block is stale (as indicated by "valid-fork" on the SecPool block too).

getchaintips considers the SecPool block as valid-fork too:

..
  {
    "height": 881780,
    "hash": "00000000000000000002745046f0bb6fab9fd306b5df8afea25e5a4cc80f9282",
    "branchlen": 1,
    "status": "valid-fork"
  },
..

[0xB10C]

I've been looking into this a bit. Based on the block ids (something that fork-observer gives the blocks), it seems like fork-observer first saw the SecPool 881780 block, then foundry's 881781, and only then foundry's 881780. Normally, this shouldn't matter but it somehow did in this case.

Restarting fork-observer helped. It correctly rebuild the header tree from the blocks in the database. This means it was either a problem with the order it saw the blocks or with one of the header tree caches with only "interesting" blocks.

For reference, these were the header ids the API returned:

[
 {'id': 109,
  'prev_id': 106,
  'height': 881780,
  'hash': '0000000000000000000185fe15f6dc0471ac83464285ff826bae53764e7d4747',
  'version': 658989056,
  'prev_blockhash': '00000000000000000001e50abf97db894680a9f8dba8b287c5d632cc577f72ed',
  'merkle_root': '3b51e83ef7f5490fbd408e8e49c0f1a1ffc228f04784feca03674b9aba0596b1',
  'time': 1738412823,
  'bits': 386046602,
  'difficulty_int': 108105433845147,
  'nonce': 285438580,
  'miner': 'Foundry USA'},
 {'id': 108,
  'prev_id': 107,
  'height': 881781,
  'hash': '00000000000000000001a7a41ecddb8ecea7a466133b8b86ad1c558f75d8ada5',
  'version': 542138368,
  'prev_blockhash': '0000000000000000000185fe15f6dc0471ac83464285ff826bae53764e7d4747',
  'merkle_root': '0c842f449a52626898ebc5eee39706ccaf612e01a6d88ed18006f7349ddef8a4',
  'time': 1738412874,
  'bits': 386046602,
  'difficulty_int': 108105433845147,
  'nonce': 961885525,
  'miner': 'Foundry USA'},
 {'id': 107,
  'prev_id': 106,
  'height': 881780,
  'hash': '00000000000000000002745046f0bb6fab9fd306b5df8afea25e5a4cc80f9282',
  'version': 973078528,
  'prev_blockhash': '00000000000000000001e50abf97db894680a9f8dba8b287c5d632cc577f72ed',
  'merkle_root': 'fe77b95e1dfdd27dd3d9b964b4f265c34a250e07157e1e3319892fbe6e1a8f94',
  'time': 1738412830,
  'bits': 386046602,
  'difficulty_int': 108105433845147,
  'nonce': 2663436214,
  'miner': 'SecPool'},
 {'id': 106,
  'prev_id': 105,
  'height': 881779,
  'hash': '00000000000000000001e50abf97db894680a9f8dba8b287c5d632cc577f72ed',
  'version': 1073733632,
  'prev_blockhash': '0000000000000000000067562b7fd073727558bd01d05651a836c0ffc86e81f4',
  'merkle_root': 'c9516d93e3c91f32dce804f9b203d26578f88bfdd771e06078e1084733af4e8c',
  'time': 1738411879,
  'bits': 386046602,
  'difficulty_int': 108105433845147,
  'nonce': 2955513315,
  'miner': 'Foundry USA'},
 {'id': 105,
  'prev_id': 104,
  'height': 881778,
  'hash': '0000000000000000000067562b7fd073727558bd01d05651a836c0ffc86e81f4',
  'version': 610598912,
  'prev_blockhash': '000000000000000000011b92341e7c8488ae59bcc155017bef19a38d4ae86c73',
  'merkle_root': 'd41614218b0a7694dc1898f337411ff5f6c07a8c62e41b468ebbd947461e4d80',
  'time': 1738411468,
  'bits': 386046602,
  'difficulty_int': 108105433845147,
  'nonce': 3458939242,
  'miner': 'AntPool'}
]

For the block with the id 108 (Foundry's 881781), the prev_id is 107 (SecPool 881780), but it should have been 109 (Foundry 881780).