fix: etcd compact err【do not merge me! only for discussion】

apisix/core/config_etcd.lua

@@ -18,7 +18,6 @@
 --- Get configuration information.
 --
 -- @module core.config_etcd
-
 local table        = require("apisix.core.table")
 local config_local = require("apisix.core.config_local")
 local log          = require("apisix.core.log")
@@ -328,21 +327,43 @@ local function sync_data(self)
         return true
     end
 
+    ::waitdir::
+    -- get latest uncompacted revision
+    local res, err = self.etcd_cli:get('/nonexisting',{
+        count_only = true,
+        range_end = "\0"
+    })
+    if err then
+        log.error("failed to get latest uncompacted revision: ", err)
+    end
+    local rev
+    if res and res.body and res.body.header and res.body.header.revision then
+        rev = tonumber(res.body.header.revision)
+    end
     local dir_res, err = waitdir(self.etcd_cli, self.key, self.prev_index + 1, self.timeout)
     log.info("waitdir key: ", self.key, " prev_index: ", self.prev_index + 1)
     log.info("res: ", json.delay_encode(dir_res, true))
-
     if not dir_res then
+        if err == "timeout" then
+            log.info("updating prev_index from "..self.prev_index.." to "..rev )
+            if rev then
+                if rev == self.prev_index then
+                    goto fail
+                end
+                self.prev_index = rev
+            end
+            goto waitdir
+        end
         if err == "compacted" then
             self.need_reload = true
             log.warn("waitdir [", self.key, "] err: ", err,
                      ", will read the configuration again via readdir")
-            return false
+            goto fail
         end
-
+        ::fail::
         return false, err
     end
-
+    log.info("waitdir success")
     local res = dir_res.body.node
     local err_msg = dir_res.body.message
     if err_msg then