api: restore httpd server on config reload

In case when httpd server serves metrics-export endpoint, updating one
server causes a deletion of its routes.

After this patch role updates httpd server on config reload and its
routes.

Closes #38

Author: themilchenko

roles/metrics-export.lua

@@ -327,7 +327,7 @@ local function disable_server(name)
 
     if server ~= nil then
         if server.httpd_name ~= nil then
-            for path, _ in pairs(server.routes) do
+            for path in pairs(server.routes) do
                 server.httpd:delete(path)
             end
         else
@@ -402,6 +402,9 @@ local function apply_http(conf)
                     -- if it isn't in applying config.
                     table.insert(listen_servers_to_start, http_servers[target.value])
                 end
+            elseif target.httpd_name ~= nil then
+                -- Update httpd value because it could change.
+                http_servers[target.value].httpd = httpd_role.get_server(target.httpd_name)
             end
 
             local server = http_servers[target.value]
@@ -427,7 +430,7 @@ local function apply_http(conf)
 
             -- Add new routes.
             for path, endpoint in pairs(new_routes) do
-                if old_routes[path] == nil then
+                if old_routes[path] == nil or httpd.iroutes[path] == nil then
                     httpd:route({
                         method = "GET",
                         path = path,

test/integration/reload_config_test.lua

@@ -3,6 +3,7 @@ local yaml = require('yaml')
 local socket = require('socket')
 local helpers = require('test.helpers')
 local server = require('test.helpers.server')
+local http_client = require('http.client'):new()
 
 local t = require('luatest')
 local g = t.group()
@@ -57,6 +58,26 @@ local function change_listen_target_in_config(cg, old_addr, new_addr)
     file:close()
 end
 
+local function change_http_addr_in_config(cg, new_addr, server_name)
+    if server_name == nil then
+      server_name = 'default'
+    end
+
+    local file = fio.open(fio.pathjoin(cg.workdir, 'config.yaml'), {'O_RDONLY'})
+    t.assert(file ~= nil)
+
+    local cfg = file:read()
+    file:close()
+
+    cfg = yaml.decode(cfg)
+    cfg.groups['group-001'].replicasets['replicaset-001'].
+                             instances.master.roles_cfg['roles.httpd'][server_name].listen = new_addr
+
+    file = fio.open(fio.pathjoin(cg.workdir, 'config.yaml'), {'O_CREAT', 'O_WRONLY', 'O_TRUNC'}, tonumber('644', 8))
+    file:write(yaml.encode(cfg))
+    file:close()
+end
+
 g.test_reload_config_update_addr = function(cg)
     cg.server = server:new({
         config_file = fio.pathjoin(cg.workdir, 'config.yaml'),
@@ -71,6 +92,7 @@ g.test_reload_config_update_addr = function(cg)
     t.assert_not(is_tcp_connect('127.0.0.2', 8082))
 
     change_listen_target_in_config(cg, '127.0.0.1:8082', '0.0.0.0:8082')
+
     cg.server:eval("require('config'):reload()")
 
     t.assert(is_tcp_connect('127.0.0.1', 8082))
@@ -100,3 +122,36 @@ g.test_reload_config_global_addr_conflict = function(cg)
       function() cg.server:eval("require('config'):reload()") end
     )
 end
+
+g.test_reload_config_routes_exists = function(cg)
+    cg.server = server:new({
+        config_file = fio.pathjoin(cg.workdir, 'config.yaml'),
+        chdir = cg.workdir,
+        alias = 'master',
+        workdir = cg.workdir,
+    })
+
+    cg.server:start({wait_until_ready = true})
+
+    local response = http_client:get('localhost:8085/metrics/prometheus')
+    t.assert_equals(response.status, 200)
+    t.assert(response.body)
+
+    local _, err = cg.server:eval("require('config'):reload()")
+    t.assert_not(err)
+
+    response = http_client:get('localhost:8085/metrics/prometheus')
+    t.assert_equals(response.status, 200)
+    t.assert(response.body)
+
+    change_http_addr_in_config(cg, 8088)
+    _, err = cg.server:eval("require('config'):reload()")
+    t.assert_not(err)
+
+    response = http_client:get('localhost:8085/metrics/prometheus')
+    t.assert_equals(response.status, 595)
+
+    response = http_client:get('localhost:8088/metrics/prometheus')
+    t.assert_equals(response.status, 200)
+    t.assert(response.body)
+end