Gossmap compaction#8903
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rustyrussell merged 23 commits intoElementsProject:masterfrom Feb 16, 2026
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Not a complete decode, just the highlights (what channel was announced or updated, what node was announced). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It didn't do anything, since the dev_compact_gossip_store command was removed. When we make it do something, it crashes since old_len is 0: ``` gossipd: gossip_store_compact: bad version gossipd: FATAL SIGNAL 6 (version v25.12rc3-1-g9e6c715-modded) ... gossipd: backtrace: ./stdlib/abort.c:79 (__GI_abort) 0x7119bd8288fe gossipd: backtrace: ./assert/assert.c:96 (__assert_fail_base) 0x7119bd82881a gossipd: backtrace: ./assert/assert.c:105 (__assert_fail) 0x7119bd83b516 gossipd: backtrace: gossipd/gossip_store.c:52 (append_msg) 0x56294de240eb gossipd: backtrace: gossipd/gossip_store.c:358 (gossip_store_compact) 0x56294 gossipd: backtrace: gossipd/gossip_store.c:395 (gossip_store_new) 0x56294de24 gossipd: backtrace: gossipd/gossmap_manage.c:455 (setup_gossmap) 0x56294de255 gossipd: backtrace: gossipd/gossmap_manage.c:488 (gossmap_manage_new) 0x56294 gossipd: backtrace: gossipd/gossipd.c:400 (gossip_init) 0x56294de22de9 ``` Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Our poor scid generation clashes badly with simplified hashing (the next patch) leading to l1's startup time when using a generated map moving from 4 seconds to 14 seconds. Under CI it actually timed out several tests. Fixing our fake scids to be more "random" reduces it to 1.5 seconds. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It's actually quite quick to load a cache-hot 308,874,377 byte gossip_store (normal -Og build), but perf does show time spent in siphash(), which is a bit overkill here, so drop that: Before: Time to load: 66718983-78037766(7.00553e+07+/-2.8e+06)nsec After: Time to load: 54510433-57991725(5.61457e+07+/-1e+06)nsec We could save maybe 10% more by disabling checksums, but having that assurance is nice. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
…changed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We also put this in the store_ended message, too: so you can tell if the equivalent_offset there really refers to this new entry (or if two or more rewrites have happened). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is the first record, and ignored by everything else. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It's used by common/gossip_store.c, which is used by many things other than gossipd. This file belongs in common. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
gossmap doesn't care, so gossipd currently has to iterate through the store to find them at startup. Create a callback for gossipd to use instead. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This way gossmap_manage can decide when to compact. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We now only need to walk it if we're doing an upgrade. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Changelog-Changed: `gossipd` no longer compacts gossip_store on startup (improving start times significantly).
This saves gossipd from converting it: ``` lightningd-1 2026-02-02T00:50:49.505Z DEBUG gossipd: Time to convert version 14 store: 890 msec ``` Reducing node startup time from 1.4 seconds to 0.5 seconds. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is the file responsible for all the writing, so it should be responsible for the rewriting if necessary (rather than gossmap_manage). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
gossip_store.c uses this to avoid two reads, and we want to use it elsewhere too. Also fix old comment on gossip_store_readhdr(). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
A new subprocess run by gossipd to create a compacted gossip store. It's pretty simple: a linear compaction of the file. Once it's done the amount it was told to, then gossipd waits until it completes the last bit. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This isn't called anywhere yet. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Changelog-Added: `gossipd` now uses a `lightning_gossip_compactd` helper to compact the gossip_store on demand, keeping it under about 210MB.
Reported-by: @daywalker90 Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
And tests! Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
…ssip_store.
Before I fixed the handling of dying channels:
```
lightning_gossipd: gossip_store: can't read hdr offset 2362/2110: Success (version v25.12-279-gb38abe6-modded)
0x6537c19ecf3a send_backtrace
common/daemon.c:38
0x6537c19f1a1d status_failed
common/status.c:207
0x6537c19e557a gossip_store_get_with_hdr
gossipd/gossip_store.c:527
0x6537c19e5613 check_msg_type
gossipd/gossip_store.c:559
0x6537c19e5a36 gossip_store_set_flag
gossipd/gossip_store.c:577
0x6537c19e5c82 gossip_store_del
gossipd/gossip_store.c:629
0x6537c19e8ddd gossmap_manage_new_block
gossipd/gossmap_manage.c:1362
0x6537c19e390e new_blockheight
gossipd/gossipd.c:430
0x6537c19e3c37 recv_req
gossipd/gossipd.c:532
0x6537c19ed22a handle_read
common/daemon_conn.c:35
0x6537c19fbe71 next_plan
ccan/ccan/io/io.c:60
0x6537c19fc174 do_plan
ccan/ccan/io/io.c:422
0x6537c19fc231 io_ready
ccan/ccan/io/io.c:439
0x6537c19fd647 io_loop
ccan/ccan/io/poll.c:470
0x6537c19e463d main
gossipd/gossipd.c:609
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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This was PR #8869 but I must have pushed only a single commit to that branch when rebasing.