wrap IPv6 addresses into square brackets

rootfs/etc/nginx/lua/balancer.lua

@@ -55,6 +55,18 @@ local function resolve_external_names(original_backend)
   return backend
 end
 
+local function format_ipv6_endpoints(endpoints)
+  local formatted_endpoints = {}
+  for _, endpoint in ipairs(endpoints) do
+    local formatted_endpoint = endpoint
+    if not endpoint.address:match("^%d+.%d+.%d+.%d+$") then
+      formatted_endpoint.address = string.format("[%s]", endpoint.address)
+    end
+    table.insert(formatted_endpoints, formatted_endpoint)
+  end
+  return formatted_endpoints
+end
+
 local function sync_backend(backend)
   local implementation = get_implementation(backend)
   local balancer = balancers[backend.name]
@@ -79,6 +91,8 @@ local function sync_backend(backend)
     backend = resolve_external_names(backend)
   end
 
+  backend.endpoints = format_ipv6_endpoints(backend.endpoints)
+
   balancer:sync(backend)
 end
 
@@ -145,7 +159,7 @@ function _M.balance()
 
   local ok, err = ngx_balancer.set_current_peer(peer)
   if not ok then
-    ngx.log(ngx.ERR, "error while setting current upstream peer: " .. tostring(err))
+    ngx.log(ngx.ERR, string.format("error while setting current upstream peer %s: %s", peer, err))
   end
 end
 

rootfs/etc/nginx/lua/test/balancer_test.lua

@@ -115,6 +115,31 @@ describe("Balancer", function()
       assert.stub(mock_instance.sync).was_called_with(mock_instance, expected_backend)
     end)
 
+    it("wraps IPv6 addresses into square brackets", function()
+      local backend = {
+        name = "exmaple-com",
+        endpoints = {
+          { address = "::1", port = "8080", maxFails = 0, failTimeout = 0 },
+          { address = "192.168.1.1", port = "8080", maxFails = 0, failTimeout = 0 },
+        }
+      }
+      local expected_backend = {
+        name = "exmaple-com",
+        endpoints = {
+          { address = "[::1]", port = "8080", maxFails = 0, failTimeout = 0 },
+          { address = "192.168.1.1", port = "8080", maxFails = 0, failTimeout = 0 },
+        }
+      }
+
+      local mock_instance = { sync = function(backend) end }
+      setmetatable(mock_instance, implementation)
+      implementation.new = function(self, backend) return mock_instance end
+      assert.has_no.errors(function() balancer.sync_backend(backend) end)
+      stub(mock_instance, "sync")
+      assert.has_no.errors(function() balancer.sync_backend(backend) end)
+      assert.stub(mock_instance.sync).was_called_with(mock_instance, expected_backend)
+    end)
+
     it("replaces the existing balancer when load balancing config changes for backend", function()
       assert.has_no.errors(function() balancer.sync_backend(backend) end)