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persistence: substrate history journaling in v2 record

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Per-substrate transition history now survives restart.  Each entry's
steady_clock timestamp is written as a system_clock-millis snapshot;
on replay the steady_clock time_point is reconstructed relative to
the current (steady_now, system_now) pair, so inter-event spacing
is preserved across restarts even if the FSM is in a different
process.  Absolute wall-clock accuracy degrades by any NTP step
that happened between write and read; that's a documented caveat.

Record format goes v1 → v2.  v1 (history-less) records still load,
just with empty history.

Test updates:
  - the old "history is NOT journaled" test is REPLACED with one
    that asserts every axis + event + label round-trips.
  - hand-crafted v1 record on disk still loads (proves backwards
    compat).
  - 15 ms-spaced events restore with their spacing intact (±slop
    for scheduler jitter).

Closes the "substrate history persistence" caveat from the post-#1-13
status writeup.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Raphael Maenle
2026-06-09 11:34:54 +02:00
parent d9f23d6db8
commit 998e81b3d8
2 changed files with 229 additions and 18 deletions
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include/secsgem/gem/store/substrates.hpp
+147 -11
View File
@@ -129,9 +129,13 @@ class SubstrateStore {
}
// ---- Persistence ----------------------------------------------------
// Records *current state* per substrate. History is not journaled —
// it's a transient in-memory ring buffer and rebuilding it from
// replayed state would be misleading.
// v2 records also journal the per-substrate transition history.
// Each entry's `at` field is written as a milliseconds-since-UNIX
// epoch wall-clock timestamp; on replay the steady_clock time_point
// is reconstructed relative to the *current* steady_now, so the
// delta between two replayed entries matches their original spacing.
// Absolute wall-clock accuracy depends on system_clock not having
// been NTP-stepped between write and read.
void enable_persistence(std::filesystem::path dir) {
namespace fs = std::filesystem;
journal_dir_ = std::move(dir);
@@ -158,7 +162,10 @@ class SubstrateStore {
install_(rec->substid, rec->carrierid, rec->slot, rec->location,
rec->loc_state, rec->proc_state, rec->id_state);
auto* s = get(rec->substid);
if (s) s->journal_path = path;
if (s) {
s->journal_path = path;
s->history = restore_history_(rec->history);
}
if (seq >= next_seq_) next_seq_ = seq + 1;
}
}
@@ -167,6 +174,17 @@ class SubstrateStore {
std::filesystem::path journal_dir() const { return journal_dir_; }
private:
// Persisted history entry — system_clock millis at write time, plus
// axis bytes and a small variant discriminator.
struct PersistedHistoryEntry {
int64_t system_ms_at_write;
SubstrateState location_to;
SubstrateProcessingState processing_to;
uint8_t event_kind; // 0 = SubstrateEvent, 1 = SubstrateProcessingEvent
uint8_t event_value; // raw enum value
std::string location_label;
};
struct Record {
std::string substid;
std::string carrierid;
@@ -175,16 +193,23 @@ class SubstrateStore {
SubstrateState loc_state;
SubstrateProcessingState proc_state;
SubstrateIDStatus id_state;
std::vector<PersistedHistoryEntry> history;
};
// Substrate record:
// [u8 magic = 0xC6][u8 version = 1]
// Substrate record (v2):
// v1 header (kept) + v2 trailer:
// [u8 magic = 0xC6][u8 version]
// [u8 loc_state][u8 proc_state][u8 id_state][u8 slot]
// [u16 substid_len][substid_len × u8]
// [u16 carrierid_len][carrierid_len × u8]
// [u16 location_len][location_len × u8]
// [u16 substid_len][substid]
// [u16 carrierid_len][carrierid]
// [u16 location_len][location]
// --- v2 trailer ---
// [u32 history_count]
// [repeat: i64 system_ms, u8 loc_to, u8 proc_to, u8 kind, u8 event,
// u16 label_len, label]
// v1 records accepted; history comes back empty.
static constexpr uint8_t kMagic = 0xC6;
static constexpr uint8_t kVersion = 0x01;
static constexpr uint8_t kVersion = 0x02;
void install_(const std::string& substid, const std::string& carrierid,
uint8_t slot, const std::string& location,
@@ -244,6 +269,51 @@ class SubstrateStore {
write_str(s->substid);
write_str(s->carrierid);
write_str(s->location);
// --- v2 history trailer ---
auto write_be32 = [&](uint32_t v) {
uint8_t b[4] = {static_cast<uint8_t>((v >> 24) & 0xFF),
static_cast<uint8_t>((v >> 16) & 0xFF),
static_cast<uint8_t>((v >> 8) & 0xFF),
static_cast<uint8_t>(v & 0xFF)};
out.write(reinterpret_cast<const char*>(b), 4);
};
auto write_be64 = [&](int64_t v) {
uint64_t u = static_cast<uint64_t>(v);
for (int i = 7; i >= 0; --i) {
uint8_t byte = static_cast<uint8_t>((u >> (i * 8)) & 0xFF);
out.put(static_cast<char>(byte));
}
};
using clk = std::chrono::steady_clock;
using sclk = std::chrono::system_clock;
const auto steady_now = clk::now();
const auto system_now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
sclk::now().time_since_epoch()).count();
write_be32(static_cast<uint32_t>(s->history.size()));
for (const auto& h : s->history) {
const auto elapsed_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
h.at - steady_now).count();
const int64_t system_ms_for_entry = system_now_ms + elapsed_ms;
write_be64(system_ms_for_entry);
out.put(static_cast<char>(h.location_to));
out.put(static_cast<char>(h.processing_to));
const uint8_t kind = std::holds_alternative<SubstrateEvent>(h.event) ? 0 : 1;
out.put(static_cast<char>(kind));
uint8_t ev_val = 0;
if (kind == 0) {
ev_val = static_cast<uint8_t>(std::get<SubstrateEvent>(h.event));
} else {
ev_val = static_cast<uint8_t>(std::get<SubstrateProcessingEvent>(h.event));
}
out.put(static_cast<char>(ev_val));
uint16_t lab_len = static_cast<uint16_t>(h.location_label.size());
uint8_t lb[2] = {static_cast<uint8_t>(lab_len >> 8),
static_cast<uint8_t>(lab_len)};
out.write(reinterpret_cast<const char*>(lb), 2);
out.write(h.location_label.data(),
static_cast<std::streamsize>(lab_len));
}
out.flush();
out.close();
std::error_code ec;
@@ -251,12 +321,44 @@ class SubstrateStore {
if (ec) fs::remove(tmp, ec);
}
// Reconstruct steady_clock::time_point from persisted system_clock millis
// by anchoring to the current (now_steady, now_system) pair. Wall-clock
// jumps between write and read will skew absolute values; deltas stay
// accurate.
static std::vector<SubstrateHistoryEntry> restore_history_(
const std::vector<PersistedHistoryEntry>& src) {
std::vector<SubstrateHistoryEntry> out;
out.reserve(src.size());
using clk = std::chrono::steady_clock;
using sclk = std::chrono::system_clock;
const auto steady_now = clk::now();
const auto system_now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
sclk::now().time_since_epoch()).count();
for (const auto& p : src) {
SubstrateHistoryEntry e;
const int64_t delta_ms = p.system_ms_at_write - system_now_ms;
e.at = steady_now + std::chrono::milliseconds(delta_ms);
e.location_to = p.location_to;
e.processing_to = p.processing_to;
e.location_label = p.location_label;
if (p.event_kind == 0) {
e.event = static_cast<SubstrateEvent>(p.event_value);
} else {
e.event = static_cast<SubstrateProcessingEvent>(p.event_value);
}
out.push_back(std::move(e));
}
return out;
}
static std::optional<Record> load_record_(const std::filesystem::path& p) {
std::ifstream in(p, std::ios::binary);
if (!in) return std::nullopt;
uint8_t header[6];
in.read(reinterpret_cast<char*>(header), sizeof(header));
if (!in || header[0] != kMagic || header[1] != kVersion) return std::nullopt;
if (!in || header[0] != kMagic) return std::nullopt;
if (header[1] != 0x01 && header[1] != 0x02) return std::nullopt;
const uint8_t version = header[1];
Record r;
r.loc_state = static_cast<SubstrateState>(header[2]);
r.proc_state = static_cast<SubstrateProcessingState>(header[3]);
@@ -274,6 +376,40 @@ class SubstrateStore {
if (!read_str(r.substid)) return std::nullopt;
if (!read_str(r.carrierid)) return std::nullopt;
if (!read_str(r.location)) return std::nullopt;
if (version >= 2) {
auto read_be32 = [&](uint32_t& v) {
uint8_t b[4];
in.read(reinterpret_cast<char*>(b), 4);
if (!in) return false;
v = (uint32_t(b[0]) << 24) | (uint32_t(b[1]) << 16) |
(uint32_t(b[2]) << 8) | uint32_t(b[3]);
return true;
};
auto read_be64 = [&](int64_t& v) {
uint8_t b[8];
in.read(reinterpret_cast<char*>(b), 8);
if (!in) return false;
uint64_t u = 0;
for (int i = 0; i < 8; ++i) u = (u << 8) | b[i];
v = static_cast<int64_t>(u);
return true;
};
uint32_t count = 0;
if (!read_be32(count)) return std::nullopt;
r.history.resize(count);
for (auto& h : r.history) {
if (!read_be64(h.system_ms_at_write)) return std::nullopt;
int b0 = in.get(); if (b0 == EOF) return std::nullopt;
int b1 = in.get(); if (b1 == EOF) return std::nullopt;
int b2 = in.get(); if (b2 == EOF) return std::nullopt;
int b3 = in.get(); if (b3 == EOF) return std::nullopt;
h.location_to = static_cast<SubstrateState>(b0);
h.processing_to = static_cast<SubstrateProcessingState>(b1);
h.event_kind = static_cast<uint8_t>(b2);
h.event_value = static_cast<uint8_t>(b3);
if (!read_str(h.location_label)) return std::nullopt;
}
}
return r;
}