feat: supports polling to select healthy nodes

lib/resty/etcd/v3.lua

@@ -27,6 +27,10 @@ local decode_base64 = ngx.decode_base64
 local semaphore     = require("ngx.semaphore")
 local health_check  = require("resty.etcd.health_check")
 
+math.randomseed(now() * 1000 + ngx.worker.pid())
+
+local INIT_COUNT_RESIZE = 2e8
+
 local _M = {}
 
 local mt = { __index = _M }
@@ -44,11 +48,25 @@ local unmodifiable_headers = {
 local refresh_jwt_token
 
 
-local function choose_endpoint(self)
+local function ring_balancer(self)
     local endpoints = self.endpoints
+    local endpoints_len = #endpoints
+
+    self.init_count = self.init_count + 1
+    local pos = self.init_count % endpoints_len + 1
+    if self.init_count >= INIT_COUNT_RESIZE then
+        self.init_count = 0
+    end
+
+    return endpoints[pos]
+end
+
 
-    for _, endpoint in ipairs(endpoints) do
+local function choose_endpoint(self)
+    for _, _ in ipairs(self.endpoints) do
+        local endpoint = ring_balancer(self)
         if health_check.get_target_status(endpoint.http_host) then
+            utils.log_info("choose endpoint: ", endpoint.http_host)
             return endpoint
         end
     end
@@ -256,6 +274,7 @@ function _M.new(opts)
     local extra_headers = opts.extra_headers
     local sni        = opts.sni
     local unix_socket_proxy = opts.unix_socket_proxy
+    local init_count = opts.init_count
 
     if not typeof.uint(timeout) then
         return nil, 'opts.timeout must be unsigned integer'
@@ -289,6 +308,10 @@ function _M.new(opts)
         return nil, 'opts.unix_socket_proxy must be string or ignore'
     end
 
+    if not typeof.number(init_count) then
+        init_count = random(100)
+    end
+
     local endpoints = {}
     local http_hosts
     if type(http_host) == 'string' then -- signle node
@@ -357,6 +380,7 @@ function _M.new(opts)
             extra_headers = extra_headers,
             sni        = sni,
             unix_socket_proxy = unix_socket_proxy,
+            init_count = init_count,
         },
         mt)
 end
@@ -888,12 +912,7 @@ local function watch(self, key, attr)
         need_cancel = need_cancel,
     }
 
-    local endpoint, err = choose_endpoint(self)
-    if not endpoint then
-        return nil, err
-    end
-
-    local callback_fun, http_cli
+    local callback_fun, http_cli, err
     callback_fun, err, http_cli = request_chunk(self, 'POST', '/watch',
                                                 opts, attr.timeout or self.timeout)
     if not callback_fun then

t/Procfile-single-enable-mtls

@@ -2,5 +2,5 @@
 etcd0: etcd
 etcd1: etcd --name infra1 --listen-client-urls https://127.0.0.1:12379 --advertise-client-urls https://127.0.0.1:12379 --listen-peer-urls http://127.0.0.1:12380 --initial-advertise-peer-urls http://127.0.0.1:12380 --initial-cluster-token etcd-cluster-1 --initial-cluster 'infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380' --initial-cluster-state new --cert-file ./t/certs/mtls_server.crt --key-file ./t/certs/mtls_server.key --client-cert-auth --trusted-ca-file ./t/certs/mtls_ca.crt
 etcd2: etcd --name infra2 --listen-client-urls https://127.0.0.1:22379 --advertise-client-urls https://127.0.0.1:22379 --listen-peer-urls http://127.0.0.1:22380 --initial-advertise-peer-urls http://127.0.0.1:22380 --initial-cluster-token etcd-cluster-1 --initial-cluster 'infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380' --initial-cluster-state new --cert-file ./t/certs/mtls_server.crt --key-file ./t/certs/mtls_server.key --client-cert-auth --trusted-ca-file ./t/certs/mtls_ca.crt
-etcd3: etcd --name infra3 --listen-client-urls https://127.0.0.1:32379 --advertise-client-urls https://127.0.0.1:32379 --listen-peer-urls http://127.0.0.1:32380 --initial-advertise-peer-urls http://127.0.0.1:32380 --initial-cluster-token etcd-cluster-1 --initial-cluster 'infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380' --initial-cluster-state new --cert-file ./t/certs/mtls_server.crt --key-file ./t/certs/mtls_server.key --client-cert-auth --trusted-ca-file ./t/certs/mtls_ca.cr
+etcd3: etcd --name infra3 --listen-client-urls https://127.0.0.1:32379 --advertise-client-urls https://127.0.0.1:32379 --listen-peer-urls http://127.0.0.1:32380 --initial-advertise-peer-urls http://127.0.0.1:32380 --initial-cluster-token etcd-cluster-1 --initial-cluster 'infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380' --initial-cluster-state new --cert-file ./t/certs/mtls_server.crt --key-file ./t/certs/mtls_server.key --client-cert-auth --trusted-ca-file ./t/certs/mtls_ca.crt
 # A learner node can be started using Procfile.learner

t/v3/health_check.t

@@ -154,6 +154,7 @@ failed to get ngx.shared dict: error_shm_name
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
             local res, err = etcd:set("/trigger_unhealthy", { a='abc'})
@@ -187,6 +188,7 @@ http://127.0.0.1:42379: connection refused
                     "http://127.0.0.1:22379",
                     "http://127.0.0.1:32379",
                 },
+                init_count = -1,
             })
 
             local body_chunk_fun, err = etcd:watch("/trigger_unhealthy")
@@ -224,10 +226,16 @@ http://127.0.0.1:42379: connection refused
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
-            etcd:set("/fault_count", { a='abc'})
-            etcd:set("/fault_count", { a='abc'})
+            -- make sure to select http://127.0.0.1:42379 twice
+            for i = 1, 4 do
+                etcd:set("/fault_count", { a='abc'})
+            end
+
+            -- here have actually been 5 reads and writes to etcd, including one to /auth/authenticate
+
             local fails, err = ngx.shared["etcd_cluster_health_check"]:get("http://127.0.0.1:42379")
             if err then
                 ngx.say(err)
@@ -264,6 +272,7 @@ GET /t
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
             etcd:set("/get_target_status", { a='abc'})
@@ -301,19 +310,21 @@ false
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
-            local res, err = etcd:set("/fail_timeout", "http://127.0.0.1:42379")  -- trigger http://127.0.0.1:42379 to unhealthy
+            local res, err
 
-            res, err = etcd:set("/fail_timeout", "http://127.0.0.1:22379") -- choose http://127.0.0.1:22379 to set value
-            res, err = etcd:get("/fail_timeout")
-            assert(res.body.kvs[1].value == "http://127.0.0.1:22379")
-
-            ngx.sleep(2)
+            -- make sure to select http://127.0.0.1:42379 once and trigger it to unhealthy
+            for i = 1, 3 do
+                 res, err = etcd:set("/fail_timeout", "value")
+            end
 
-            res, err = etcd:set("/fail_timeout", "http://127.0.0.1:42379") -- choose http://127.0.0.1:42379 to set value
-            res, err = etcd:get("/fail_timeout")
-            assert(res.body.kvs[1].value == "http://127.0.0.1:22379")
+            -- ensure that unhealthy http://127.0.0.1:42379 are no longer selected
+            for i = 1, 3 do
+                 res, err = etcd:get("/fail_timeout")
+                 assert(res.body.kvs[1].value == "value")
+            end
 
             ngx.say("done")
         }
@@ -323,6 +334,8 @@ GET /t
 --- timeout: 5
 --- response_body
 done
+--- error_log
+update endpoint: http://127.0.0.1:42379 to unhealthy
 --- no_error_log
 [error]
 
@@ -387,6 +400,7 @@ has no healthy etcd endpoint available
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
             local etcd2, err = require "resty.etcd" .new({
@@ -398,6 +412,7 @@ has no healthy etcd endpoint available
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
             assert(tostring(etcd1) ~= tostring(etcd2))
@@ -493,12 +508,21 @@ qr/update endpoint: http:\/\/localhost:1984 to unhealthy/
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
-            local res, err = etcd:set("/trigger_unhealthy", "abc")
+            local res, err
+            for i = 1, 3 do
+                res, err = etcd:set("/trigger_unhealthy", "abc")
+            end
             check_res(res, err)
             local res, err = etcd:get("/trigger_unhealthy")
             check_res(res, err, "abc")
+
+            -- There are 5 times read and write operations to etcd have occurred here
+            -- 3 set, 1 get, 1 auth
+            -- actual 8 times choose endpoint, retry every time 42379 is selected
+            -- 42379 marked as unhealthy after 3 seleced
         }
     }
 --- request
@@ -531,13 +555,16 @@ checked val as expect: abc
                 },
                 user = 'root',
                 password = 'abc123',
+                init_count = -1,
             })
 
             local body_chunk_fun, err = etcd:watch("/trigger_unhealthy", {timeout = 0.5})
             check_res(body_chunk_fun, err)
 
             ngx.timer.at(0.1, function ()
-                etcd:set("/trigger_unhealthy", "abc")
+                for i = 1, 3 do
+                    etcd:set("/trigger_unhealthy", "abc")
+                end
             end)
 
             local idx = 0
@@ -563,6 +590,8 @@ qr/update endpoint: http:\/\/127.0.0.1:42379 to unhealthy/
 --- response_body_like eval
 qr/1:.*"created":true.*
 2:.*"value":"abc".*
+3:.*"value":"abc".*
+4:.*"value":"abc".*
 timeout/
 --- timeout: 5
 
@@ -681,6 +710,7 @@ has no healthy etcd endpoint available
                     "http://127.0.0.1:22379",
                     "http://127.0.0.1:32379",
                 },
+                init_count = -1,
             })
 
             local res, err = etcd:set("/test/etcd/healthy", "hello")
@@ -749,6 +779,7 @@ qr/update endpoint: http:\/\/127.0.0.1:12379 to unhealthy/
                     "http://127.0.0.1:22379",
                     "http://127.0.0.1:32379",
                 },
+                init_count = -1,
             })
 
             local res
@@ -827,6 +858,7 @@ healthy check use ngx.shared dict
                     "http://127.0.0.1:22379",
                     "http://127.0.0.1:32379",
                 },
+                init_count = -1,
             })
 
             local res
@@ -844,7 +876,7 @@ healthy check use ngx.shared dict
 GET /t
 --- response_body
 http://127.0.0.1:42379: connection refused
-http://127.0.0.1:42379: connection refused
+http://127.0.0.1:22379: OK
 --- no_error_log eval
 qr/update endpoint: http:\/\/127.0.0.1:42379 to unhealthy/
 
@@ -889,3 +921,39 @@ GET /t
 --- response_body
 passed
 passed
+
+
+
+=== TEST 22: ring balancer with specific init_count
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua_block {
+            local health_check = require("resty.etcd.health_check")
+            health_check.disable()
+            local etcd, err = require "resty.etcd" .new({
+                protocol = "v3",
+                http_host = {
+                    "http://127.0.0.1:12379",
+                    "http://127.0.0.1:22379",
+                    "http://127.0.0.1:32379",
+                },
+                init_count = 101,
+            })
+
+            local res
+            for i = 1, 3 do
+                res, _ = etcd:set("/ring_balancer", "abc")
+            end
+
+            ngx.say(etcd.init_count)
+        }
+    }
+--- request
+GET /t
+--- response_body
+104
+--- error_log
+choose_endpoint(): choose endpoint: http://127.0.0.1:12379
+choose_endpoint(): choose endpoint: http://127.0.0.1:22379
+choose_endpoint(): choose endpoint: http://127.0.0.1:32379