Store Downloads Die: Merging Chunks Failed

[blitz]

cellerd complains:

Apr 17 15:54:32 plausible cellerd[212999]: 2026-04-17T13:54:32.955914Z ERROR attic_server::api::binary_cache: Merging chunks failed e=streaming error

This error needs to be more debuggable:

• What caused this error?
• Can we do anything about it?

[blitz]

Best way to reproduce it:

$ wget https://cache.x86.lol/blitz/nar/3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar
--2026-04-22 09:11:22--  https://cache.x86.lol/blitz/nar/3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar
Resolving cache.x86.lol (cache.x86.lol)... 128.140.124.143, 2a01:4f8:c013:4e4d::1
Connecting to cache.x86.lol (cache.x86.lol)|128.140.124.143|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-nix-nar]
Saving to: ‘3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar’

3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.     [    <=>                                                     ]   1.03M  28.1KB/s    in 38s

2026-04-22 09:13:00 (28.1 KB/s) - Read error at byte 1081273 (Success).Retrying.

--2026-04-22 09:13:01--  (try: 2)  https://cache.x86.lol/blitz/nar/3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar
Connecting to cache.x86.lol (cache.x86.lol)|128.140.124.143|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-nix-nar]
Saving to: ‘3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar’

3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.     [ <=>                                                        ]   3.99K  14.4KB/s               ^3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.     [    <=>                                                     ]   1.07M  18.1KB/s    in 61s

2026-04-22 09:15:03 (18.1 KB/s) - Read error at byte 1118796 (Success).Retrying.

--2026-04-22 09:15:05--  (try: 3)  https://cache.x86.lol/blitz/nar/3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar
Connecting to cache.x86.lol (cache.x86.lol)|128.140.124.143|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-nix-nar]
Saving to: ‘3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar’

3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.     [    <=>                                                     ]   1.04M  17.9KB/s    in 59s

2026-04-22 09:17:05 (17.9 KB/s) - Read error at byte 1118796 (Success).Retrying.

--2026-04-22 09:17:08--  (try: 4)  https://cache.x86.lol/blitz/nar/3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar
Connecting to cache.x86.lol (cache.x86.lol)|128.140.124.143|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-nix-nar]
Saving to: ‘3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.nar’

3wrl5dpd4vcfhqb6112ib5kmm3mqfm8h.     [   <=>                                                      ] 707.61K   760KB/s