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restore: keep the full and incremental snapshot pair matched #12568

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Merged
mjain-jump merged 7 commits into from
Nov 3, 2026
+335 −37
Merged

restore: keep the full and incremental snapshot pair matched #12568

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2b85c87
restore: ignore an incremental built on an older full
mjain-jump Oct 28, 2026
0f56123
snapct: request the incremental snapshot by file name
mjain-jump Oct 28, 2026
2451765
snapct: harden the remembered incremental peer
mjain-jump Oct 29, 2026
4538ef5
snapct: skip a ping-banned server in the incremental fallback
mjain-jump Nov 3, 2026
7f44f35
snapct: use the incremental fallback while waiting for peers
mjain-jump Nov 3, 2026
2811ed1
snapct: tidy the re-pin and local full prediction
mjain-jump Nov 3, 2026
32f26d1
snapct: drop a comment
mjain-jump Nov 3, 2026
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82 changes: 60 additions & 22 deletions src/discof/restore/fd_snapct_tile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -207,10 +207,11 @@ struct fd_snapct_tile {
uchar in_kind[ FD_TOPO_MAX_TILE_IN_LINKS ];

struct {
ulong full_slot;
ulong slot;
int pending;
int committed;
ulong full_slot;
ulong slot;
int pending;
int committed;
fd_sspeer_t peer; /* peer last picked for an incremental on full_slot */
} predicted_incremental;

struct {
Expand Down Expand Up @@ -408,13 +409,31 @@ predict_incremental( fd_snapct_tile_t * ctx ) {
fd_sspeer_t best = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );

if( FD_LIKELY( best.addr.l ) ) {
ctx->predicted_incremental.peer = best;
Comment thread
mjain-jump marked this conversation as resolved.
Resolved
if( FD_UNLIKELY( ctx->predicted_incremental.slot!=best.incr_slot ) ) {
ctx->predicted_incremental.slot = best.incr_slot;
ctx->predicted_incremental.pending = 1;
}
}
}

/* best_incremental_peer picks the peer to download the incremental
from. A server that made a new full while our full loaded no
longer offers an incremental on ours, but the newest one we saw is
still on its disk. */

static fd_sspeer_t
best_incremental_peer( fd_snapct_tile_t * ctx ) {
fd_sspeer_t best = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );
if( FD_UNLIKELY( !best.addr.l &&
ctx->predicted_incremental.peer.addr.l &&
ctx->predicted_incremental.peer.full_slot==ctx->predicted_incremental.full_slot &&
!fd_ssping_is_invalidated( ctx->ssping, ctx->predicted_incremental.peer.addr ) ) ) {
best = ctx->predicted_incremental.peer;
}
return best;
}

static void
on_resolve( void * _ctx,
fd_sspeer_key_t const * key,
Expand Down Expand Up @@ -701,7 +720,7 @@ init_load( fd_snapct_tile_t * ctx,
else fd_memcpy( out->snapshot_hash, ctx->peer.incr_hash, FD_HASH_FOOTPRINT );
}

out->is_redirect = !file; /* always use redirect for HTTP downloads */
out->is_redirect = !file && full;

if( file ) out->file_sz = full ? ctx->local_in.full_snapshot_size : ctx->local_in.incremental_snapshot_size;
else out->file_sz = 0UL;
Expand All @@ -712,18 +731,14 @@ init_load( fd_snapct_tile_t * ctx,
ctx->start_sent = 0;
ctx->load_complete = 0;

if( !file ) {
FD_TEST( fd_cstr_printf_check( full ? ctx->http_full_snapshot_name : ctx->http_incr_snapshot_name,
PATH_MAX, NULL, full ? "snapshot.tar.bz2" : "incremental-snapshot.tar.bz2" ) );
snapshot_output_prepare( ctx, full );
}
/* The full learns its name from the redirect, the incremental gets
its name at START, and a local file has none. Clear stale names
before the rename functions run. */
if( !full ) fd_cstr_fini( ctx->http_incr_snapshot_name );
else if( file ) fd_cstr_fini( ctx->http_full_snapshot_name );
else FD_TEST( fd_cstr_printf_check( ctx->http_full_snapshot_name, PATH_MAX, NULL, "snapshot.tar.bz2" ) );

/* Clear stale http_*_snapshot_name for file loads before rename
functions run. GUI publish is deferred to the META handler. */
if( file ) {
if( full ) fd_cstr_fini( ctx->http_full_snapshot_name );
else fd_cstr_fini( ctx->http_incr_snapshot_name );
}
if( !file ) snapshot_output_prepare( ctx, full );

if( !full ) {
if( file ) ctx->predicted_incremental.slot = ctx->local_in.incremental_snapshot_slot;
Expand Down Expand Up @@ -788,6 +803,12 @@ blacklist_peer( fd_snapct_tile_t * ctx ) {
fd_ssping_invalidate( ctx->ssping, ctx->peer.addr, fd_clock_tile_now( ctx->clock ) );
fd_sspeer_selector_remove_by_addr( ctx->selector, ctx->peer.addr );
fd_sspeer_selector_process_cluster_slot( ctx->selector );

if( ctx->predicted_incremental.peer.addr.l==ctx->peer.addr.l ||
fd_sspeer_key_eq( &ctx->predicted_incremental.peer.key, &ctx->peer.key ) ) {
ctx->predicted_incremental.peer.addr.l = 0UL;
}

if( FD_UNLIKELY( blacklist_map_ele_query( ctx->blacklist_map, &ctx->peer.key, NULL, ctx->blacklist_pool ) ) ) return;
if( FD_LIKELY( blacklist_pool_free( ctx->blacklist_pool ) ) ) {
fd_sspeer_blacklist_entry_t * bl = blacklist_pool_ele_acquire( ctx->blacklist_pool );
Expand Down Expand Up @@ -948,7 +969,11 @@ after_credit( fd_snapct_tile_t * ctx,
if( full ) {
FD_TEST( fd_cstr_printf_check( out->path, PATH_MAX, &out->path_len, "/snapshot.tar.bz2" ) );
} else {
FD_TEST( fd_cstr_printf_check( out->path, PATH_MAX, &out->path_len, "/incremental-snapshot.tar.bz2" ) );
char hash_b58[ FD_BASE58_ENCODED_32_SZ ];
fd_base58_encode_32( ctx->peer.incr_hash, NULL, hash_b58 );
FD_TEST( fd_cstr_printf_check( ctx->http_incr_snapshot_name, PATH_MAX, NULL, "incremental-snapshot-%lu-%lu-%s.tar.zst",
ctx->predicted_incremental.full_slot, ctx->predicted_incremental.slot, hash_b58 ) );
FD_TEST( fd_cstr_printf_check( out->path, PATH_MAX, &out->path_len, "/%s", ctx->http_incr_snapshot_name ) );
}

/* Peers outside the config list use HTTP without a hostname. */
Expand Down Expand Up @@ -1046,7 +1071,7 @@ after_credit( fd_snapct_tile_t * ctx,
}

FD_TEST( ctx->predicted_incremental.full_slot!=FD_SSPEER_SLOT_UNKNOWN );
fd_sspeer_t best = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );
fd_sspeer_t best = best_incremental_peer( ctx );
if( FD_LIKELY( best.addr.l ) ) {
set_state( ctx, FD_SNAPCT_STATE_COLLECTING_PEERS_INCREMENTAL );
ctx->deadline_nanos = now;
Expand Down Expand Up @@ -1188,6 +1213,7 @@ after_credit( fd_snapct_tile_t * ctx,
FD_LOG_INFO(( "reading full snapshot at slot %lu (cluster full %lu incremental %lu) from local file `%s`",
ctx->local_in.full_snapshot_slot, cluster.full, cluster.incremental, ctx->local_in.full_snapshot_path ));
ctx->predicted_incremental.full_slot = ctx->local_in.full_snapshot_slot;
if( !local_incr_on_disk ) predict_incremental( ctx );
set_state( ctx, FD_SNAPCT_STATE_READING_FULL_FILE );
init_load( ctx, stem, 1, 1 );
} else {
Expand Down Expand Up @@ -1227,6 +1253,7 @@ after_credit( fd_snapct_tile_t * ctx,
ctx->peer = best;
set_state( ctx, FD_SNAPCT_STATE_READING_FULL_HTTP );
ctx->predicted_incremental.full_slot = best.full_slot;
predict_incremental( ctx );
init_load( ctx, stem, 1, 0 );
}
break;
Expand All @@ -1236,7 +1263,7 @@ after_credit( fd_snapct_tile_t * ctx,
case FD_SNAPCT_STATE_COLLECTING_PEERS_INCREMENTAL: {
if( FD_UNLIKELY( now<ctx->deadline_nanos ) ) break;

fd_sspeer_t best = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );
fd_sspeer_t best = best_incremental_peer( ctx );
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Resolved
if( FD_UNLIKELY( !best.addr.l ) ) {
if( !ctx->download_enabled ) {
if( FD_UNLIKELY( wfs_short_of_target( ctx, ctx->predicted_incremental.full_slot ) ) ) {
Expand Down Expand Up @@ -1402,7 +1429,7 @@ after_credit( fd_snapct_tile_t * ctx,

ulong fetch_incr = ULONG_MAX;
if( FD_LIKELY( ctx->download_enabled ) ) {
fd_sspeer_t best_incr = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );
fd_sspeer_t best_incr = best_incremental_peer( ctx );
if( FD_LIKELY( best_incr.addr.l ) ) fetch_incr = best_incr.incr_slot;
}

Expand Down Expand Up @@ -1471,7 +1498,7 @@ after_credit( fd_snapct_tile_t * ctx,
}

/* Get the best incremental peer to download from */
fd_sspeer_t best = fd_sspeer_selector_best( ctx->selector, 1, ctx->predicted_incremental.full_slot, wfs_floor( ctx ) );
fd_sspeer_t best = best_incremental_peer( ctx );
if( FD_UNLIKELY( !best.addr.l ) ) {
ctx->deadline_nanos = now;
set_state( ctx, FD_SNAPCT_STATE_COLLECTING_PEERS_INCREMENTAL );
Expand Down Expand Up @@ -1933,7 +1960,17 @@ snapld_frag( fd_snapct_tile_t * ctx,
}
} else {
if( full ) fd_cstr_ncpy( ctx->http_full_snapshot_name, meta->resolved_name, PATH_MAX );
else fd_cstr_ncpy( ctx->http_incr_snapshot_name, meta->resolved_name, PATH_MAX );

/* The server sent a newer full than the one we picked. The
incremental has to be built on the full we actually load. */
if( FD_UNLIKELY( full && meta->resolved_slot!=ULONG_MAX && meta->resolved_slot!=ctx->predicted_incremental.full_slot ) ) {
FD_LOG_NOTICE(( "full snapshot resolved to slot %lu instead of %lu, pairing the incremental snapshot with it",
meta->resolved_slot, ctx->predicted_incremental.full_slot ));
ctx->predicted_incremental.full_slot = meta->resolved_slot;
ctx->predicted_incremental.slot = FD_SSPEER_SLOT_UNKNOWN;
predict_incremental( ctx );
if( ctx->predicted_incremental.slot==FD_SSPEER_SLOT_UNKNOWN ) send_expected_slot( ctx, stem, meta->resolved_slot );
}

if( FD_LIKELY( !!ctx->out_gui.mem ) ) {
char snapshot_path[ PATH_MAX+30UL ]; /* 30 is fd_cstr_nlen( "https://255.255.255.255:65536/", ULONG_MAX ) */
Expand Down Expand Up @@ -2495,6 +2532,7 @@ unprivileged_init( fd_topo_t const * topo,
ctx->predicted_incremental.slot = FD_SSPEER_SLOT_UNKNOWN;
ctx->predicted_incremental.pending = 0;
ctx->predicted_incremental.committed = 0;
fd_memset( &ctx->predicted_incremental.peer, 0, sizeof(fd_sspeer_t) );

fd_memset( &ctx->metrics, 0, sizeof(ctx->metrics) );

Expand Down
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