[Tarantool-patches] [PATCH v2] replication: add box.info.replication_anon

[Serge Petrenko <sergepetrenko@tarantool.org>]

Closes #4900

@TarantoolBot document
Title: add new field to box.info: replication_anon

It is now possible to list all the anonymous replicas following the
instance with a call to `box.info.replication_anon()`
The output is similar to the one produced by `box.info.replication` with
an exception that anonymous replicas are indexed by their uuid strings
rather then server ids, since server ids have no meaning for anonymous
replicas.

Example:
```
tarantool> box.info.replication_anon
---
- []
...

tarantool> box.info.replication_anon()
---
- 02757524-1887-4c75-9137-d5c191fba507:
    id: 0
    uuid: 02757524-1887-4c75-9137-d5c191fba507
    lsn: 0
    downstream:
      status: follow
      idle: 0.43651100000716
      vclock: {1: 1}
  937a8292-8f99-4d11-aede-b97e9f5e9473:
    id: 0
    uuid: 937a8292-8f99-4d11-aede-b97e9f5e9473
    lsn: 0
    downstream:
      status: follow
      idle: 0.5189309999987
      vclock: {1: 1}
...

```

Note, that anonymous replicas hide their lsn from the others, so
anonymous replica lsn will always be reported as zero, even if anonymous
replicas perform some local space operations.
To know the anonymous replica's lsn, you have to issue `box.info.lsn` on
it.
---
https://github.com/tarantool/tarantool/issues/4900
https://github.com/tarantool/tarantool/tree/sp/gh-4900-list-anon-replicas

Changes in v2:
  - move anon replicas output to
    box.info.replication_anon()

@ChangeLog
  - Add `box.info.replication_anon`. When called, it lists anonymous replicas
    in the same format as `box.info.replication`, the only exception is that
    anon replicas are indexed by their uuid strings (gh-4900).

 src/box/lua/info.c             | 45 ++++++++++++++++++++++++++++++++++
 test/box/info.result           |  1 +
 test/replication/anon.result   | 24 +++++++++++++++---
 test/replication/anon.test.lua | 11 +++++++--
 4 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/src/box/lua/info.c b/src/box/lua/info.c
index a789f7822..c4f90bda1 100644
--- a/src/box/lua/info.c
+++ b/src/box/lua/info.c
@@ -214,6 +214,50 @@ lbox_info_replication(struct lua_State *L)
 	return 1;
 }
 
+static int
+lbox_info_replication_anon_call(struct lua_State *L)
+{
+	lua_newtable(L); /* box.info.replication_anon */
+
+	/* Nice formatting */
+	lua_newtable(L); /* metatable */
+	lua_pushliteral(L, "mapping");
+	lua_setfield(L, -2, "__serialize");
+	lua_setmetatable(L, -2);
+
+	replicaset_foreach(replica) {
+		if (!replica->anon)
+			continue;
+
+		lua_pushstring(L, tt_uuid_str(&replica->uuid));
+		lbox_pushreplica(L, replica);
+
+		lua_settable(L, -3);
+	}
+
+	return 1;
+}
+
+static int
+lbox_info_replication_anon(struct lua_State *L)
+{
+	/*
+	 * Make the .replication_anon field callable in order to
+	 * not flood the output with possibly lots of anonymous
+	 * replicas on box.info call.
+	 */
+	lua_newtable(L);
+
+	lua_newtable(L); /* metatable */
+
+	lua_pushstring(L, "__call");
+	lua_pushcfunction(L, lbox_info_replication_anon_call);
+	lua_settable(L, -3);
+
+	lua_setmetatable(L, -2);
+	return 1;
+}
+
 static int
 lbox_info_id(struct lua_State *L)
 {
@@ -534,6 +578,7 @@ static const struct luaL_Reg lbox_info_dynamic_meta[] = {
 	{"vclock", lbox_info_vclock},
 	{"ro", lbox_info_ro},
 	{"replication", lbox_info_replication},
+	{"replication_anon", lbox_info_replication_anon},
 	{"status", lbox_info_status},
 	{"uptime", lbox_info_uptime},
 	{"pid", lbox_info_pid},
diff --git a/test/box/info.result b/test/box/info.result
index e6d0ba6aa..40eeae069 100644
--- a/test/box/info.result
+++ b/test/box/info.result
@@ -83,6 +83,7 @@ t
   - package
   - pid
   - replication
+  - replication_anon
   - ro
   - signature
   - sql
diff --git a/test/replication/anon.result b/test/replication/anon.result
index cbbeeef09..f3f9c60ed 100644
--- a/test/replication/anon.result
+++ b/test/replication/anon.result
@@ -151,10 +151,28 @@ test_run:cmd('switch default')
  | - true
  | ...
 
--- Replica isn't visible on master.
-#box.info.replication
+-- Test box.info.replication_anon.
+box.info.replication_anon
+ | ---
+ | - []
+ | ...
+#box.info.replication_anon()
+ | ---
+ | - 0
+ | ...
+uuid, tbl = next(box.info.replication_anon())
+ | ---
+ | ...
+-- Anonymous replicas are indexed by uuid strings.
+require("uuid").fromstr(uuid) ~= nil
+ | ---
+ | - true
+ | ...
+-- Anonymous replicas share box.info representation with
+-- normal replicas.
+tbl.downstream.status
  | ---
- | - 1
+ | - follow
  | ...
 
 -- Test that replication (even anonymous) from an anonymous
diff --git a/test/replication/anon.test.lua b/test/replication/anon.test.lua
index 627dc5c8e..fef72d07d 100644
--- a/test/replication/anon.test.lua
+++ b/test/replication/anon.test.lua
@@ -50,8 +50,15 @@ box.space.loc:truncate()
 
 test_run:cmd('switch default')
 
--- Replica isn't visible on master.
-#box.info.replication
+-- Test box.info.replication_anon.
+box.info.replication_anon
+#box.info.replication_anon()
+uuid, tbl = next(box.info.replication_anon())
+-- Anonymous replicas are indexed by uuid strings.
+require("uuid").fromstr(uuid) ~= nil
+-- Anonymous replicas share box.info representation with
+-- normal replicas.
+tbl.downstream.status
 
 -- Test that replication (even anonymous) from an anonymous
 -- instance is forbidden. An anonymous replica will fetch
-- 
2.21.1 (Apple Git-122.3)