Add cluster scale down test

Covers new behaviour of updating slotmap due to error.

tests/CMakeLists.txt

@@ -252,3 +252,7 @@ add_test(NAME redirect-with-hostname-test-async
 if(hiredis_VERSION VERSION_EQUAL "1.1.0" OR hiredis_VERSION VERSION_EQUAL "0")
   set_tests_properties(redirect-with-hostname-test-async PROPERTIES DISABLED True)
 endif()
+add_test(NAME cluster-scale-down-test
+         COMMAND "${CMAKE_SOURCE_DIR}/tests/scripts/cluster-scale-down-test.sh"
+                "$<TARGET_FILE:clusterclient>"
+         WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}/tests/scripts/")

tests/scripts/cluster-scale-down-test.sh

@@ -0,0 +1,91 @@
+#!/bin/sh
+#
+# Simulate a 3 node cluster where:
+# - 'nodeid3' is removed before the client has connected to it.
+# - 'nodeid2' is removed after the client has already connected to it.
+#
+# Usage: $0 /path/to/clusterclient-binary
+
+clientprog=${1:-./clusterclient}
+testname=cluster-scale-down-test
+
+# Sync processes waiting for CONT signals.
+perl -we 'use sigtrap "handler", sub{exit}, "CONT"; sleep 1; die "timeout"' &
+syncpid1=$!;
+perl -we 'use sigtrap "handler", sub{exit}, "CONT"; sleep 1; die "timeout"' &
+syncpid2=$!;
+
+# Start simulated redis node #1
+timeout 5s ./simulated-redis.pl -p 7401 -d --sigcont $syncpid1 <<'EOF' &
+# Initial slotmap.
+EXPECT CONNECT
+EXPECT ["CLUSTER", "SLOTS"]
+SEND [[0, 5000, ["127.0.0.1", 7401, "nodeid1"]],[5001, 10000, ["127.0.0.1", 7402, "nodeid2"]],[10001, 16383, ["127.0.0.1", 7403, "nodeid3"]]]
+EXPECT CLOSE
+
+# Connect failure to nodeid3 triggers a slotmap update.
+EXPECT CONNECT
+EXPECT ["CLUSTER", "SLOTS"]
+SEND [[0, 8000, ["127.0.0.1", 7401, "nodeid1"]],[8001, 16383, ["127.0.0.1", 7402, "nodeid2"]]]
+EXPECT CLOSE
+
+# The send failure of "GET {foo}2" triggers a slotmap update when sending "GET {foo}3".
+EXPECT CONNECT
+EXPECT ["CLUSTER", "SLOTS"]
+SEND [[0, 16383, ["127.0.0.1", 7401, "nodeid1"]]]
+EXPECT CLOSE
+EXPECT CONNECT
+EXPECT ["GET", "{foo}3"]
+SEND "bar3"
+EXPECT CLOSE
+EOF
+server1=$!
+
+# Start simulated redis node #2
+timeout 5s ./simulated-redis.pl -p 7402 -d --sigcont $syncpid2 <<'EOF' &
+EXPECT CONNECT
+EXPECT ["GET", "{foo}1"]
+SEND "bar1"
+# Forced close. The next command "GET {foo}2" will fail.
+CLOSE
+EOF
+server2=$!
+
+# Wait until both nodes are ready to accept client connections
+wait $syncpid1 $syncpid2;
+
+# Run client
+timeout 3s "$clientprog" 127.0.0.1:7401 > "$testname.out" <<'EOF'
+GET {foo}1
+GET {foo}2
+GET {foo}3
+EOF
+clientexit=$?
+
+# Wait for servers to exit
+wait $server1; server1exit=$?
+wait $server2; server2exit=$?
+
+# Check exit statuses
+if [ $server1exit -ne 0 ]; then
+    echo "Simulated server #1 exited with status $server1exit"
+    exit $server1exit
+fi
+if [ $server2exit -ne 0 ]; then
+    echo "Simulated server #2 exited with status $server2exit"
+    exit $server2exit
+fi
+if [ $clientexit -ne 0 ]; then
+    echo "$clientprog exited with status $clientexit"
+    exit $clientexit
+fi
+
+# Check the output from clusterclient
+expected="bar1
+error: Server closed the connection
+bar3"
+
+echo "$expected" | diff -u - "$testname.out" || exit 99
+
+# Clean up
+rm "$testname.out"