crimson/osd: sketch the backfill machine and its interfaces.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>

diff --git a/src/crimson/osd/backfill_state.h b/src/crimson/osd/backfill_state.h
new file mode 100644 (file)
index 0000000..21015a4
--- /dev/null
+++ b/src/crimson/osd/backfill_state.h
@@ -0,0 +1,119 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <boost/statechart/custom_reaction.hpp>
+#include <boost/statechart/event.hpp>
+#include <boost/statechart/event_base.hpp>
+#include <boost/statechart/simple_state.hpp>
+#include <boost/statechart/state.hpp>
+#include <boost/statechart/state_machine.hpp>
+#include <boost/statechart/transition.hpp>
+
+#include "osd/recovery_types.h"
+
+namespace crimson::osd {
+
+namespace sc = boost::statechart;
+
+struct BackfillState {
+  struct BackfillListener;
+
+  // events comes first
+  struct PrimaryScanned : sc::event<PrimaryScanned> {
+    BackfillInterval result;
+  };
+
+  struct ReplicaScanned : sc::event<ReplicaScanned> {
+    pg_shard_t from;
+    BackfillInterval result;
+  };
+
+  struct Flushed : sc::event<Flushed> {
+  };
+
+  struct Triggered : sc::event<Triggered> {
+  };
+
+  struct Initial;
+  struct Enqueuing;
+
+  class BackfillMachine : public sc::state_machine<BackfillMachine, Initial> {
+  };
+
+  // states
+  struct Crashed : sc::state<Crashed, BackfillMachine>, NamedState {
+  };
+
+  struct Initial : sc::state<Initial, BackfillMachine>, NamedState {
+    using reactions = boost::mpl::list<
+      sc::custom_reaction<Triggered>,
+      sc::transition<sc::event_base, Crashed>>;
+    // initialize after triggering backfill by on_activate_complete().
+    // transit to Enqueuing.
+    sc::result react(const Triggered&);
+  };
+
+  struct Enqueuing : sc::state<Enqueuing, BackfillMachine>, NamedState {
+    using reactions = boost::mpl::list<
+      sc::transition<sc::event_base, Crashed>>;
+  };
+
+  struct PrimaryScanning : sc::state<PrimaryScanning, BackfillMachine>,
+                           NamedState {
+    using reactions = boost::mpl::list<
+      sc::custom_reaction<PrimaryScanned>,
+      sc::transition<sc::event_base, Crashed>>;
+    // collect scanning result and transit to Enqueuing.
+    sc::result react(const PrimaryScanned&);
+  };
+
+  struct ReplicasScanning : sc::state<ReplicasScanning, BackfillMachine>,
+                            NamedState {
+    using reactions = boost::mpl::list<
+      sc::custom_reaction<ReplicaScanned>,
+      sc::transition<sc::event_base, Crashed>>;
+    // collect scanning result; if all results are collected, transition
+    // to Enqueuing will happen.
+    sc::result react(const ReplicaScanned&);
+  };
+
+  struct Flushing : sc::simple_state<Flushing, BackfillMachine>,
+                    NamedState {
+    using reactions = boost::mpl::list<
+      sc::transition<Flushed, Enqueuing>,
+      sc::transition<sc::event_base, Crashed>>;
+  };
+};
+
+struct BackfillState::BackfillListener {
+  virtual void request_replica_scan(
+    const pg_shard_t& target,
+    const hobject_t& begin,
+    const hobject_t& end) = 0;
+
+  virtual void request_primary_scan(
+    const hobject_t& begin) = 0;
+
+  virtual void enqueue_push(
+    const pg_shard_t& target,
+    const hobject_t& obj,
+    const eversion_t& v) = 0;
+
+  virtual void enqueue_drop(
+    const pg_shard_t& target,
+    const hobject_t& obj,
+    const eversion_t& v) = 0;
+
+  virtual void update_peers_last_backfill(
+    const hobject_t& new_last_backfill) = 0;
+
+  virtual bool budget_available() const = 0;
+
+  virtual void backfilled() = 0;
+
+  virtual ~BackfillListener() = default;
+};
+
+} // namespace crimson::osd