[couchdb] 05/06: Condition cache storage/eviction on db_version

[da...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

davisp pushed a commit to branch prototype/fdb-layer-db-version-as-vstamps
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit d2646711140ddc9c4c1359fa343ebd386beed681
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Thu Jun 4 15:54:01 2020 -0500

    Condition cache storage/eviction on db_version
    
    Now that db_version is comparable we can use that for cache control.
---
 src/fabric/src/fabric2_server.erl         | 10 +++++-----
 src/fabric/test/fabric2_db_misc_tests.erl | 23 ++++++++++++++---------
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/src/fabric/src/fabric2_server.erl b/src/fabric/src/fabric2_server.erl
index b557da8..067cf49 100644
--- a/src/fabric/src/fabric2_server.erl
+++ b/src/fabric/src/fabric2_server.erl
@@ -94,12 +94,12 @@ store(#{name := DbName} = Db0) when is_binary(DbName) ->
 maybe_update(#{name := DbName} = Db0) when is_binary(DbName) ->
     #{
         uuid := UUID,
-        md_version := MDVer
+        db_version := DBVer
     } = Db0,
     Db1 = sanitize(Db0),
     Head = {DbName, UUID,  '$1', '_'},
-    Guard = {'=<', '$1', MDVer},
-    Body = {DbName, UUID, MDVer, {const, Db1}},
+    Guard = {'=<', '$1', DBVer},
+    Body = {DbName, UUID, DBVer, {const, Db1}},
     try
         1 =:= ets:select_replace(?MODULE, [{Head, [Guard], [{Body}]}])
     catch
@@ -116,10 +116,10 @@ remove(DbName) when is_binary(DbName) ->
 maybe_remove(#{name := DbName} = Db) when is_binary(DbName) ->
     #{
         uuid := UUID,
-        md_version := MDVer
+        db_version := DBVer
     } = Db,
     Head = {DbName, UUID, '$1', '_'},
-    Guard = {'=<', '$1', MDVer},
+    Guard = {'=<', '$1', DBVer},
     1 =:= ets:select_delete(?MODULE, [{Head, [Guard], [true]}]).
 
 
diff --git a/src/fabric/test/fabric2_db_misc_tests.erl b/src/fabric/test/fabric2_db_misc_tests.erl
index a8a2677..cad91a5 100644
--- a/src/fabric/test/fabric2_db_misc_tests.erl
+++ b/src/fabric/test/fabric2_db_misc_tests.erl
@@ -340,13 +340,18 @@ metadata_bump({DbName, _, _}) ->
     % Perform a random operation which calls ensure_current
     {ok, _} = fabric2_db:get_db_info(Db),
 
+    % After previous operation, the cache should have been cleared
+    ?assertMatch(undefined, fabric2_server:fetch(DbName, undefined)),
+
+    % Call open again and check that we have the latest db version
+    {ok, Db2} = fabric2_db:open(DbName, [{user_ctx, ?ADMIN_USER}]),
+
     % Check that db handle in the cache got the new metadata version
     % and that check_current_ts was updated
-    CachedDb = fabric2_server:fetch(DbName, undefined),
     ?assertMatch(#{
         md_version := NewMDVersion,
         check_current_ts := Ts
-    } when Ts >= TsBeforeEnsureCurrent, CachedDb).
+    } when Ts >= TsBeforeEnsureCurrent, Db2).
 
 
 db_version_bump({DbName, _, _}) ->
@@ -358,12 +363,12 @@ db_version_bump({DbName, _, _}) ->
     % regular db open + update security doc or something like that to make sure
     % we don't touch the local cache
     #{db_prefix := DbPrefix} = Db,
-    DbVersionKey = erlfdb_tuple:pack({?DB_VERSION}, DbPrefix),
     {ok, Fdb} = application:get_env(fabric, db),
-    NewDbVersion = fabric2_util:uuid(),
     erlfdb:transactional(Fdb, fun(Tx) ->
-        erlfdb:set(Tx, DbVersionKey, NewDbVersion),
-        erlfdb:set_versionstamped_value(Tx, ?METADATA_VERSION_KEY, <<0:112>>)
+        DbVersionKey = erlfdb_tuple:pack({?DB_VERSION}, DbPrefix),
+        DbVersion = fabric2_fdb:new_versionstamp(Tx),
+        DbVersionVal = erlfdb_tuple:pack_vs({DbVersion}),
+        ok = erlfdb:set_versionstamped_value(Tx, DbVersionKey, DbVersionVal)
     end),
 
     % Perform a random operation which calls ensure_current
@@ -375,15 +380,15 @@ db_version_bump({DbName, _, _}) ->
     % Call open again and check that we have the latest db version
     {ok, Db2} = fabric2_db:open(DbName, [{user_ctx, ?ADMIN_USER}]),
 
-    % Check that db handle in the cache got the new metadata version
-    ?assertMatch(#{db_version := NewDbVersion}, Db2).
+    % Check that db handle in the cache got a newer version
+    ?assert(maps:get(db_version, Db) < maps:get(db_version, Db2)).
 
 
 db_cache_doesnt_evict_newer_handles({DbName, _, _}) ->
     {ok, Db} = fabric2_db:open(DbName, [{user_ctx, ?ADMIN_USER}]),
     CachedDb = fabric2_server:fetch(DbName, undefined),
 
-    StaleDb = Db#{md_version := <<0>>},
+    StaleDb = Db#{db_version := <<0>>},
 
     ok = fabric2_server:store(StaleDb),
     ?assertEqual(CachedDb, fabric2_server:fetch(DbName, undefined)),