Retry auths when using the "resty" http ng backend

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fix 3scale Batcher policy failing to cache and report requests containing app ID only [PR #956](https://github.com/3scale/apicast/pull/956), [THREESCALE-1515](https://issues.jboss.org/browse/THREESCALE-1515)
+- Auths against the 3scale backend are now retried when using the 3scale batching policy [PR #961](https://github.com/3scale/apicast/pull/961)
 
 ## [3.4.0-rc2] - 2018-11-16
 

gateway/src/apicast/backend_client.lua

@@ -24,6 +24,7 @@ local backend_calls_metrics = require('apicast.metrics.3scale_backend_calls')
 
 local http_proxy = require('resty.http.proxy')
 local http_ng_ngx = require('resty.http_ng.backend.ngx')
+local http_ng_resty = require('resty.http_ng.backend.resty')
 -- resty.http_ng.backend.ngx is using ngx.location.capture, which is available only
 -- on rewrite, access and content phases. We need to use cosockets (http_ng default backend)
 -- everywhere else (like timers).
@@ -207,6 +208,19 @@ local function format_transactions(reports_batch)
   return res
 end
 
+-- This is a temporary fix.
+-- We know that auths are idempotent so they can be retried safely when there
+-- is an error caused by the 3scale backend closing the connection.
+-- In the future, we should probably include the logic for retries in the
+-- different backends of the http ng libs.
+-- This only works with the "resty" backend because the "ngx" has its own logic
+-- for retrying.
+local function retry_auth(auth_resp, http_backend)
+  return http_backend == http_ng_resty and
+         auth_resp.status == 0 and
+         auth_resp.error == "closed"
+end
+
 --- Call authrep (oauth_authrep) on backend.
 -- @tparam ?{table,...} query list of query parameters
 -- @treturn http_ng.response http response
@@ -236,6 +250,10 @@ function _M:authorize(...)
   local auth_uri = auth_path(using_oauth)
   local res = call_backend_transaction(self, auth_uri, authorize_options(using_oauth), ...)
 
+  if retry_auth(res, self.http_client.backend) then
+    res = call_backend_transaction(self, auth_uri, authorize_options(using_oauth), ...)
+  end
+
   inc_metrics('auth', res.status)
 
   return res

spec/backend_client_spec.lua

@@ -1,6 +1,7 @@
 local _M = require('apicast.backend_client')
 local configuration = require('apicast.configuration')
 local http_ng = require 'resty.http_ng'
+local http_ng_resty = require 'resty.http_ng.backend.resty'
 local ReportsBatch = require 'apicast.policy.3scale_batcher.reports_batch'
 local backend_calls_metrics = require 'apicast.metrics.3scale_backend_calls'
 
@@ -197,6 +198,19 @@ describe('backend client', function()
 
       assert.stub(backend_calls_metrics.report).was_called_with('auth', status)
     end)
+
+    it('retries when auth return a "closed" error and uses the "resty" http backend', function()
+      local service = configuration.parse_service({ id = '42' })
+
+      local backend_client = assert(_M:new(service, http_ng_resty))
+      stub(backend_client.http_client, 'get').returns(
+        { status = 0, error = 'closed' }
+      )
+
+      backend_client:authorize()
+
+      assert.stub(backend_client.http_client.get).was_called(2)
+    end)
   end)
 
   describe('report', function()