[couchdb] 01/01: Create new on_compact trigger

[da...@apache.org]

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davisp pushed a commit to branch COUCHDB-3326-clustered-purge-pr4-on-compact-plugin
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 1499c79808c7a3d1c9a7bcbd3dfc3bb75e0e1ec3
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Wed May 30 14:34:44 2018 -0500

    Create new on_compact trigger
    
    This trigger allows any storage engine that makes use of compaction to
    notify that compaction is starting. This is preparatory work for
    clustered indexes so that existing indexes are allowed to ensure they
    have a clustered purge local doc before compaction runs.
    
    COUCHDB-3326
    
    Co-Authored-By: jiangphcn <ji...@cn.ibm.com>
---
 src/couch/src/couch_bt_engine_compactor.erl |  2 ++
 src/couch/src/couch_db_engine.erl           | 31 ++++++++++++++++++++++++++++-
 src/couch/src/couch_db_plugin.erl           |  5 +++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/couch/src/couch_bt_engine_compactor.erl b/src/couch/src/couch_bt_engine_compactor.erl
index 4e52064..2c5b78e 100644
--- a/src/couch/src/couch_bt_engine_compactor.erl
+++ b/src/couch/src/couch_bt_engine_compactor.erl
@@ -44,6 +44,8 @@ start(#st{} = St, DbName, Options, Parent) ->
     } = St,
     couch_log:debug("Compaction process spawned for db \"~s\"", [DbName]),
 
+    couch_db_engine:trigger_on_compact(DbName),
+
     {ok, NewSt, DName, DFd, MFd, Retry} =
             open_compaction_files(Header, FilePath, Options),
     erlang:monitor(process, MFd),
diff --git a/src/couch/src/couch_db_engine.erl b/src/couch/src/couch_db_engine.erl
index 4974201..2fe0b0d 100644
--- a/src/couch/src/couch_db_engine.erl
+++ b/src/couch/src/couch_db_engine.erl
@@ -627,7 +627,8 @@
     count_changes_since/2,
 
     start_compaction/1,
-    finish_compaction/2
+    finish_compaction/2,
+    trigger_on_compact/1
 ]).
 
 
@@ -891,3 +892,31 @@ finish_compaction(Db, CompactInfo) ->
     end,
     ok = gen_server:call(couch_server, {db_updated, NewDb}, infinity),
     {ok, NewDb}.
+
+
+trigger_on_compact(DbName) ->
+    {ok, DDocs} = get_ddocs(DbName),
+    couch_db_plugin:on_compact(DbName, DDocs).
+
+
+get_ddocs(<<"shards/", _/binary>> = DbName) ->
+    {_, Ref} = spawn_monitor(fun() ->
+        exit(fabric:design_docs(mem3:dbname(DbName)))
+    end),
+    receive
+        {'DOWN', Ref, _, _, {ok, JsonDDocs}} ->
+            {ok, lists:map(fun(JsonDDoc) ->
+                couch_doc:from_json_obj(JsonDDoc)
+            end, JsonDDocs)};
+        {'DOWN', Ref, _, _, Else} ->
+            Else
+    end;
+get_ddocs(DbName) ->
+    couch_util:with_db(DbName, fun(Db) ->
+        FoldFun = fun(FDI, Acc) ->
+            Doc = couch_db:open_doc_int(Db, FDI, []),
+            {ok, [Doc | Acc]}
+        end,
+        {ok, Docs} = couch_db:fold_design_docs(Db, FoldFun, [], []),
+        {ok, lists:reverse(Docs)}
+    end).
diff --git a/src/couch/src/couch_db_plugin.erl b/src/couch/src/couch_db_plugin.erl
index 740b812..8163256 100644
--- a/src/couch/src/couch_db_plugin.erl
+++ b/src/couch/src/couch_db_plugin.erl
@@ -18,6 +18,7 @@
     after_doc_read/2,
     validate_docid/1,
     check_is_admin/1,
+    on_compact/2,
     on_delete/2
 ]).
 
@@ -56,6 +57,10 @@ check_is_admin(Db) ->
     %% callbacks return true only if it specifically allow the given Id
     couch_epi:any(Handle, ?SERVICE_ID, check_is_admin, [Db], []).
 
+on_compact(DbName, DDocs) ->
+    Handle = couch_epi:get_handle(?SERVICE_ID),
+    couch_epi:apply(Handle, ?SERVICE_ID, on_compact, [DbName, DDocs], []).
+
 on_delete(DbName, Options) ->
     Handle = couch_epi:get_handle(?SERVICE_ID),
     couch_epi:apply(Handle, ?SERVICE_ID, on_delete, [DbName, Options], []).