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Add WAL persistence to VSR log

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Port the Write-Ahead Log implementation from raft/ into the VSR
server. Log entries are now written to disk with FNV-1a checksums
and fsynced before updating in-memory state. On startup, the WAL
file is loaded and validated, replacing the boot marker for crash
detection. View changes and recovery use atomic rename (tmp.log ->
vsr.log) to replace the WAL safely.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
cozis
2026-02-22 16:28:39 +01:00
co-authored by Claude Opus 4.6
parent 487f3bf010
commit 5688860719
10 changed files with 503 additions and 136 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/invariant_checker.c
+17 -17
View File
@@ -164,9 +164,9 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
// 1. commit_index <= log.count
// A node cannot have committed more entries than it has in its log.
if (s->commit_index > s->log.count) {
if (s->commit_index > s->wal.count) {
fprintf(stderr, "INVARIANT VIOLATED: node %d: commit_index (%d) > log.count (%d)\n",
i, s->commit_index, s->log.count);
i, s->commit_index, s->wal.count);
__builtin_trap();
}
@@ -206,11 +206,11 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
// 9. Log entry view numbers must not exceed the node's current view.
// Entries are created in the view they were proposed. No entry
// should carry a view number from the future.
for (int k = 0; k < s->log.count; k++) {
if ((uint64_t)s->log.entries[k].view_number > s->view_number) {
for (int k = 0; k < s->wal.count; k++) {
if ((uint64_t)s->wal.entries[k].view_number > s->view_number) {
fprintf(stderr, "INVARIANT VIOLATED: node %d: log[%d].view_number (%d) "
"> view_number (%lu)\n",
i, k, s->log.entries[k].view_number,
i, k, s->wal.entries[k].view_number,
(unsigned long)s->view_number);
__builtin_trap();
}
@@ -221,8 +221,8 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
// votes for its own entries.
if (s->status == STATUS_NORMAL && is_leader(s)) {
int idx = self_idx(s);
for (int k = s->commit_index; k < s->log.count; k++) {
if (!(s->log.entries[k].votes & (1 << idx))) {
for (int k = s->commit_index; k < s->wal.count; k++) {
if (!(s->wal.entries[k].votes & (1 << idx))) {
fprintf(stderr, "INVARIANT VIOLATED: node %d (leader): "
"uncommitted log[%d] missing leader's own vote bit\n",
i, k);
@@ -266,7 +266,7 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
mc = nodes[j]->commit_index;
for (int k = 0; k < mc; k++) {
if (memcmp(&nodes[i]->log.entries[k].oper, &nodes[j]->log.entries[k].oper, sizeof(MetaOper)) != 0) {
if (memcmp(&nodes[i]->wal.entries[k].oper, &nodes[j]->wal.entries[k].oper, sizeof(MetaOper)) != 0) {
fprintf(stderr, "INVARIANT VIOLATED: committed log operation mismatch at index %d "
"between node %d and node %d\n", k, i, j);
__builtin_trap();
@@ -298,11 +298,11 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
if (source_node_idx >= 0 && observed_max_commit > ic->shadow_count) {
ServerState *source = nodes[source_node_idx];
assert(source->log.count >= observed_max_commit);
assert(source->wal.count >= observed_max_commit);
for (int k = ic->shadow_count; k < observed_max_commit; k++) {
MetaOper *source_oper = &source->log.entries[k].oper;
MetaOper *source_oper = &source->wal.entries[k].oper;
// Cross-validate against other live non-recovering nodes
// that have also committed this entry.
@@ -315,10 +315,10 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
continue;
if (nodes[j]->commit_index <= k)
continue;
if (nodes[j]->log.count <= k)
if (nodes[j]->wal.count <= k)
continue;
if (memcmp(&nodes[j]->log.entries[k].oper, source_oper, sizeof(MetaOper)) != 0) {
if (memcmp(&nodes[j]->wal.entries[k].oper, source_oper, sizeof(MetaOper)) != 0) {
fprintf(stderr, "INVARIANT VIOLATED: committed entry mismatch at index %d "
"between source node %d and node %d during shadow log append\n",
k, source_node_idx, j);
@@ -340,15 +340,15 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
for (int i = 0; i < num_nodes; i++) {
if (nodes[i] == NULL)
continue;
if (nodes[i]->log.count <= k)
if (nodes[i]->wal.count <= k)
continue;
if (nodes[i]->commit_index <= k)
continue;
if (memcmp(&nodes[i]->log.entries[k].oper, &ic->shadow_log[k], sizeof(MetaOper)) != 0) {
if (memcmp(&nodes[i]->wal.entries[k].oper, &ic->shadow_log[k], sizeof(MetaOper)) != 0) {
char shadow_buf[128], node_buf[128];
meta_snprint_oper(shadow_buf, sizeof(shadow_buf), &ic->shadow_log[k]);
meta_snprint_oper(node_buf, sizeof(node_buf), &nodes[i]->log.entries[k].oper);
meta_snprint_oper(node_buf, sizeof(node_buf), &nodes[i]->wal.entries[k].oper);
fprintf(stderr, "INVARIANT VIOLATED: shadow log mismatch at index %d on node %d\n"
" shadow: %s\n"
" node: %s\n",
@@ -377,9 +377,9 @@ void invariant_checker_run(InvariantChecker *ic, ServerState **nodes, int num_no
num_dead++;
continue;
}
if (nodes[i]->log.count <= k)
if (nodes[i]->wal.count <= k)
continue;
if (memcmp(&nodes[i]->log.entries[k].oper, &ic->shadow_log[k], sizeof(MetaOper)) == 0)
if (memcmp(&nodes[i]->wal.entries[k].oper, &ic->shadow_log[k], sizeof(MetaOper)) == 0)
holders++;
}