[PATCH] replication: fix bug with zero replication_connect_quorum

[Konstantin Belyavskiy <k.belyavskiy@tarantool.org>]

If 'box.cfg.read_only' is false, 'replication' defines at least one
replica (other than itself), but they are not available at the time
of box.cfg execution and replication_connect_quorum is set to zero,
master displays 'orphan' status instead of 'running' since logic
which cnange this state is executed only after successfull connection.

ticket: https://github.com/tarantool/tarantool/issues/3278
branch: https://github.com/tarantool/tarantool/compare/gh-3278-fix-bug-with-zero-replication-connect-quorum

Closes #3278
---
 src/box/replication.cc              |  8 ++++--
 test/replication/quorum.result      | 52 +++++++++++++++++++++++++++++++++++++
 test/replication/quorum.test.lua    | 25 ++++++++++++++++++
 test/replication/replica_params.lua | 23 ++++++++++++++++
 4 files changed, 106 insertions(+), 2 deletions(-)
 create mode 100644 test/replication/replica_params.lua

diff --git a/src/box/replication.cc b/src/box/replication.cc
index b1c84d36c..760f83751 100644
--- a/src/box/replication.cc
+++ b/src/box/replication.cc
@@ -600,8 +600,12 @@ error:
 void
 replicaset_follow(void)
 {
-	if (replicaset.applier.total == 0) {
-		/* Replication is not configured. */
+	if (replicaset.applier.total == 0 || replicaset_quorum() == 0) {
+		/*
+		 * Replication is not configured or quorum is set to
+		 * zero so in the latter case we have no need to wait
+		 * for others.
+		 */
 		box_clear_orphan();
 		return;
 	}
diff --git a/test/replication/quorum.result b/test/replication/quorum.result
index 34408d421..78d98bfa2 100644
--- a/test/replication/quorum.result
+++ b/test/replication/quorum.result
@@ -239,3 +239,55 @@ test_run:cmd('switch default')
 test_run:drop_cluster(SERVERS)
 ---
 ...
+--
+-- gh-3278: test different replication and replication_connect_quorum configs.
+--
+-- For next test try to find port with no tarantool running on it.
+remote = require('net.box')
+---
+...
+attempt = 0
+---
+...
+port = 32768 + math.random(32768)
+---
+...
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+while attempt < 10 do
+    s = remote.connect('localhost:'..port)
+    if s.state ~= 'error' then
+        port = 32768 + math.random(32768)
+        attempt = attempt + 1
+    else
+        break
+    end
+end;
+---
+...
+test_run:cmd("setopt delimiter ''");
+---
+- true
+...
+test_run:cmd("create server replica with rpl_master=default, script='replication/replica_params.lua'")
+---
+- true
+...
+test_run:cmd("start server replica with args='0 0 "..port.."'")
+---
+- true
+...
+test_run:cmd("restart server replica with args='0 1 "..port.."'")
+---
+- true
+...
+test_run:cmd('switch replica')
+---
+- true
+...
+box.info.status -- running (old: orphan)
+---
+- running
+...
diff --git a/test/replication/quorum.test.lua b/test/replication/quorum.test.lua
index 856006843..d92ed23a6 100644
--- a/test/replication/quorum.test.lua
+++ b/test/replication/quorum.test.lua
@@ -97,3 +97,28 @@ box.info.replication[4].upstream.status
 -- Cleanup.
 test_run:cmd('switch default')
 test_run:drop_cluster(SERVERS)
+
+--
+-- gh-3278: test different replication and replication_connect_quorum configs.
+--
+
+-- For next test try to find port with no tarantool running on it.
+remote = require('net.box')
+attempt = 0
+port = 32768 + math.random(32768)
+test_run:cmd("setopt delimiter ';'")
+while attempt < 10 do
+    s = remote.connect('localhost:'..port)
+    if s.state ~= 'error' then
+        port = 32768 + math.random(32768)
+        attempt = attempt + 1
+    else
+        break
+    end
+end;
+test_run:cmd("setopt delimiter ''");
+test_run:cmd("create server replica with rpl_master=default, script='replication/replica_params.lua'")
+test_run:cmd("start server replica with args='0 0 "..port.."'")
+test_run:cmd("restart server replica with args='0 1 "..port.."'")
+test_run:cmd('switch replica')
+box.info.status -- running (old: orphan)
diff --git a/test/replication/replica_params.lua b/test/replication/replica_params.lua
new file mode 100644
index 000000000..4f8ee5d0a
--- /dev/null
+++ b/test/replication/replica_params.lua
@@ -0,0 +1,23 @@
+#!/usr/bin/env tarantool
+
+local quorum = tonumber(arg[1])
+local n_replics = tonumber(arg[2])
+local addr = '127.0.0.1:'..arg[3]
+listen = os.getenv("LISTEN")
+-- Test different replicaset configurations:
+-- First, when the only address in the replicaset is itself.
+repl = {}
+-- To test situation with second master unavailable, add
+-- second address (should be empty).
+if n_replics == 1 then repl = { addr } end
+if n_replics == 2 then repl = { listen, addr } end
+
+box.cfg({
+    listen              = listen,
+    replication         = repl,
+    memtx_memory        = 100 * 1024 * 1024,
+    replication_connect_quorum = quorum,
+    replication_connect_timeout = 0.1,
+})
+
+require('console').listen(os.getenv('ADMIN'))
-- 
2.14.3 (Apple Git-98)