Four bugs caused data mismatches between PUT and GET operations:
1. chunk_store_exists() used file_open (O_CREAT) to check if a chunk
file exists, which created empty files as a side effect. Servers
would then read from these empty files and return uninitialized
heap memory as chunk data. Fixed by using file_exists (access())
instead.
2. Server's process_fetch_chunk checked `ret < 0` after
chunk_store_read, missing the EOF case (ret == 0) from empty
files. Changed to `ret <= 0`.
3. begin_transfers() == 0 was used as a completion check in both
STEP_FETCH_CHUNK and STEP_STORE_CHUNK, but returning 0 only means
"no new transfers started", not "all done". With concurrent chunk
transfers, this caused premature completion, leaving in-flight
transfers to hit UNREACHABLE. Fixed by using
all_chunk_transfers_completed() instead.
4. choose_store_locations_for_chunk() returned [0, 1] for ALL chunks
regardless of index, while GET fetches chunk i from servers
(i+j) % num_servers. This made some chunks unreachable. Fixed by
using (chunk_idx + j) % num_servers for store locations.
Also added SO_REUSEADDR to the server listen socket so restarting
the cluster doesn't fail with "Couldn't setup TCP listener", and
added a note on mock_access about the simulation mismatch.
https://claude.ai/code/session_01JniNxxDP4NbsDXNGmGNG7H
Two changes to improve code coverage in deterministic simulation testing:
1. Add 3 chunk servers (was 1) to match the replication factor
- This enables testing of chunk replication and chunk-to-chunk
server communication code paths in chunk_server.c
- Covers: process_chunk_server_download_*, start_download,
download_targets_* functions
2. Fix Quakey bug where events targeting a closed descriptor caused
assertion failures
- Added remove_events_targeting_desc() to clean up DISCONNECT and
DATA events when a descriptor is freed
- Modified desc_free() to accept Sim pointer and call cleanup
- This was exposed by running multiple chunk servers which create
more connection activity
Three related issues were causing the simulation to get stuck:
1. Network events (connect, disconnect, send_data) were scheduled with
relative times instead of absolute times, causing events to be
scheduled in the past once simulation time exceeded 10-100ms.
2. When DATA events couldn't be fully consumed (receiver buffer full),
they stayed at their original time, preventing time from advancing.
Now they are rescheduled to current_time + 10ms.
3. When poll_timeout was 0, WAKEUP events were created at current_time,
causing an infinite loop where time never advanced. Now timeout=0
sets timedout immediately without creating an event.
Claude
cozis