Snapshot Work - Interim Commit

Some initial work to get snapshots going.

Changes required, as need to snapshot through the Bookie to ensure that
there is no race between extracting the Bookie's in-memory view and the
Penciller's view if a push_to_mem has occurred inbetween.

A lot still outstanding, especially around Inker snapshots, and handling
timeouts

src/leveled_inker.erl

@@ -103,7 +103,7 @@
         ink_get/3,
         ink_fetch/3,
         ink_loadpcl/4,
-        ink_snap/1,
+        ink_registersnapshot/2,
         ink_close/1,
         ink_print_manifest/1,
         build_dummy_journal/0,
@@ -146,8 +146,8 @@ ink_get(Pid, PrimaryKey, SQN) ->
 ink_fetch(Pid, PrimaryKey, SQN) ->
     gen_server:call(Pid, {fetch, PrimaryKey, SQN}, infinity).
 
-ink_snap(Pid) ->
-    gen_server:call(Pid, snapshot, infinity).
+ink_registersnapshot(Pid, Requestor) ->
+    gen_server:call(Pid, {snapshot, Requestor}, infinity).
 
 ink_close(Pid) ->
     gen_server:call(Pid, close, infinity).
@@ -163,39 +163,20 @@ ink_print_manifest(Pid) ->
 %%%============================================================================
 
 init([InkerOpts]) ->
-    RootPath = InkerOpts#inker_options.root_path,
-    CDBopts = InkerOpts#inker_options.cdb_options,
-    JournalFP = filepath(RootPath, journal_dir),
-    {ok, JournalFilenames} = case filelib:is_dir(JournalFP) of
-        true ->
-            file:list_dir(JournalFP);
-        false ->
-            filelib:ensure_dir(JournalFP),
-            {ok, []}
-    end,
-    ManifestFP = filepath(RootPath, manifest_dir),
-    {ok, ManifestFilenames} = case filelib:is_dir(ManifestFP) of
-        true ->
-            file:list_dir(ManifestFP);
-        false ->
-            filelib:ensure_dir(ManifestFP),
-            {ok, []}
-    end,
-    {Manifest,
-        {ActiveJournal, LowActiveSQN},
-        JournalSQN,
-        ManifestSQN} = build_manifest(ManifestFilenames,
-                                        JournalFilenames,
-                                        fun simple_manifest_reader/2,
-                                        RootPath,
-                                        CDBopts),
-    {ok, #state{manifest = lists:reverse(lists:keysort(1, Manifest)),
-                    manifest_sqn = ManifestSQN,
-                    journal_sqn = JournalSQN,
-                    active_journaldb = ActiveJournal,
-                    active_journaldb_sqn = LowActiveSQN,
-                    root_path = RootPath,
-                    cdb_options = CDBopts}}.
+    case {InkerOpts#inker_options.root_path,
+            InkerOpts#inker_options.start_snapshot} of
+        {undefined, true} ->
+            SrcInker = InkerOpts#inker_options.source_inker,
+            Requestor = InkerOpts#inker_options.requestor,
+            {ok,
+                {ActiveJournalDB,
+                    Manifest}} = ink_registersnapshot(SrcInker, Requestor),            
+            {ok, #state{manifest=Manifest,
+                            active_journaldb=ActiveJournalDB}};
+            %% Need to do something about timeout
+        {_RootPath, false} ->
+            start_from_file(InkerOpts)
+    end.
 
 
 handle_call({put, Key, Object, KeyChanges}, From, State) ->
@@ -240,12 +221,11 @@ handle_call({load_pcl, StartSQN, FilterFun, Penciller}, _From, State) ->
                         State#state.active_journaldb}],
     Reply = load_from_sequence(StartSQN, FilterFun, Penciller, Manifest),
     {reply, Reply, State};
-handle_call(snapshot, _From , State) ->
+handle_call({register_snapshot, _Requestor}, _From , State) ->
     %% TODO: Not yet implemented registration of snapshot
     %% Should return manifest and register the snapshot
     {reply, {State#state.manifest,
-                State#state.active_journaldb,
-                State#state.active_journaldb_sqn},
+                State#state.active_journaldb},
                 State};
 handle_call(print_manifest, _From, State) ->
     manifest_printer(State#state.manifest),
@@ -275,6 +255,42 @@ code_change(_OldVsn, State, _Extra) ->
 %%% Internal functions
 %%%============================================================================
 
+start_from_file(InkerOpts) ->
+    RootPath = InkerOpts#inker_options.root_path,
+    CDBopts = InkerOpts#inker_options.cdb_options,
+    JournalFP = filepath(RootPath, journal_dir),
+    {ok, JournalFilenames} = case filelib:is_dir(JournalFP) of
+        true ->
+            file:list_dir(JournalFP);
+        false ->
+            filelib:ensure_dir(JournalFP),
+            {ok, []}
+    end,
+    ManifestFP = filepath(RootPath, manifest_dir),
+    {ok, ManifestFilenames} = case filelib:is_dir(ManifestFP) of
+        true ->
+            file:list_dir(ManifestFP);
+        false ->
+            filelib:ensure_dir(ManifestFP),
+            {ok, []}
+    end,
+    {Manifest,
+        {ActiveJournal, LowActiveSQN},
+        JournalSQN,
+        ManifestSQN} = build_manifest(ManifestFilenames,
+                                        JournalFilenames,
+                                        fun simple_manifest_reader/2,
+                                        RootPath,
+                                        CDBopts),
+    {ok, #state{manifest = lists:reverse(lists:keysort(1, Manifest)),
+                    manifest_sqn = ManifestSQN,
+                    journal_sqn = JournalSQN,
+                    active_journaldb = ActiveJournal,
+                    active_journaldb_sqn = LowActiveSQN,
+                    root_path = RootPath,
+                    cdb_options = CDBopts}}.
+
+
 put_object(PrimaryKey, Object, KeyChanges, State) ->
     NewSQN = State#state.journal_sqn + 1,
     %% TODO: The term goes through a double binary_to_term conversion