throw exceptions on HTTPTooManyRequests and HTTPServerError so FluentD will retry

fluentd/fluent-plugin-grafana-loki/.rubocop.yml

@@ -13,7 +13,7 @@ Metrics/BlockLength:
   Max: 60
 Metrics/MethodLength:
   Max: 50
-Metrics/LineLength:
+Layout/LineLength:
   Max: 120
 Metrics/ClassLength:
   Max: 150
@@ -25,3 +25,9 @@ RSpec/ExampleLength:
   Max: 100
 RSpec/MultipleExpectations:
   Max: 10
+Style/HashEachMethods:
+  Enabled: true
+Style/HashTransformKeys:
+  Enabled: true
+Style/HashTransformValues:
+  Enabled: true

fluentd/fluent-plugin-grafana-loki/Gemfile

@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 
 gemspec
 
-gem 'fluentd', '1.9.0'
+gem 'fluentd', '1.9.3'
 gem 'rubocop-rspec'
 gem 'simplecov', require: false, group: :test
 gem 'test-unit'

fluentd/fluent-plugin-grafana-loki/lib/fluent/plugin/out_loki.rb

@@ -15,6 +15,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+require 'fluent/env'
 require 'fluent/plugin/output'
 require 'net/http'
 require 'yajl'
@@ -26,6 +27,8 @@ module Plugin
     class LokiOutput < Fluent::Plugin::Output # rubocop:disable Metrics/ClassLength
       Fluent::Plugin.register_output('loki', self)
 
+      class LogPostError < StandardError; end
+
       helpers :compat_parameters, :record_accessor
 
       attr_accessor :record_accessors
@@ -131,29 +134,16 @@ def write(chunk)
         body = { 'streams' => payload }
 
         # add ingest path to loki url
+        res = loki_http_request(body)
 
-        req = Net::HTTP::Post.new(
-          @uri.request_uri
-        )
-        req.add_field('Content-Type', 'application/json')
-        req.add_field('X-Scope-OrgID', @tenant) if @tenant
-        req.body = Yajl.dump(body)
-        req.basic_auth(@username, @password) if @username
-
-        opts = ssl_opts(@uri)
+        return if res.is_a?(Net::HTTPSuccess)
 
-        log.debug "sending #{req.body.length} bytes to loki"
-        res = Net::HTTP.start(@uri.host, @uri.port, **opts) { |http| http.request(req) }
-        unless res&.is_a?(Net::HTTPSuccess)
-          res_summary = if res
-                          "#{res.code} #{res.message} #{res.body}"
-                        else
-                          'res=nil'
-                        end
-          log.warn "failed to #{req.method} #{@uri} (#{res_summary})"
-          log.debug Yajl.dump(body)
+        res_summary = "#{res.code} #{res.message} #{res.body}"
+        log.warn "failed to write post to #{@uri} (#{res_summary})"
+        log.debug Yajl.dump(body)
 
-        end
+        # Only retry 429 and 500s
+        raise(LogPostError, res_summary) if res.is_a?(Net::HTTPTooManyRequests) || res.is_a?(Net::HTTPServerError)
       end
 
       def ssl_opts(uri)
@@ -186,6 +176,22 @@ def generic_to_loki(chunk)
 
       private
 
+      def loki_http_request(body)
+        req = Net::HTTP::Post.new(
+          @uri.request_uri
+        )
+        req.add_field('Content-Type', 'application/json')
+        req.add_field('X-Scope-OrgID', @tenant) if @tenant
+        req.body = Yajl.dump(body)
+        req.basic_auth(@username, @password) if @username
+
+        opts = ssl_opts(@uri)
+
+        log.debug "sending #{req.body.length} bytes to loki"
+
+        Net::HTTP.start(@uri.host, @uri.port, **opts) { |http| http.request(req) }
+      end
+
       def numeric?(val)
         !Float(val).nil?
       rescue StandardError

fluentd/fluent-plugin-grafana-loki/spec/gems/fluent/plugin/loki_output_spec.rb

@@ -244,4 +244,37 @@
     expect(res[0]['stream']).to eq('stream' => 'stdout')
     6.times { |i| expect(res[0]['values'][i][1]).to eq i.to_s }
   end
+
+  it 'raises an LogPostError when http request is not successful' do
+    config = <<-CONF
+      url     https://logs-us-west1.grafana.net
+    CONF
+    driver = Fluent::Test::Driver::Output.new(described_class)
+    driver.configure(config)
+    lines = [[Time.at(1_546_270_458), { 'message' => 'foobar', 'stream' => 'stdout' }]]
+
+    # 200
+    success = Net::HTTPSuccess.new(1.0, 200, 'OK')
+    allow(driver.instance).to receive(:loki_http_request) { success }
+    allow(success).to receive(:body).and_return('fake body')
+    expect { driver.instance.write(lines) }.not_to raise_error
+
+    # 205
+    success = Net::HTTPSuccess.new(1.0, 205, 'OK')
+    allow(driver.instance).to receive(:loki_http_request) { success }
+    allow(success).to receive(:body).and_return('fake body')
+    expect { driver.instance.write(lines) }.not_to raise_error
+
+    # 429
+    too_many_requests = Net::HTTPTooManyRequests.new(1.0, 429, 'OK')
+    allow(driver.instance).to receive(:loki_http_request) { too_many_requests }
+    allow(too_many_requests).to receive(:body).and_return('fake body')
+    expect { driver.instance.write(lines) }.to raise_error(described_class::LogPostError)
+
+    # 505
+    server_error = Net::HTTPServerError.new(1.0, 505, 'OK')
+    allow(driver.instance).to receive(:loki_http_request) { server_error }
+    allow(server_error).to receive(:body).and_return('fake body')
+    expect { driver.instance.write(lines) }.to raise_error(described_class::LogPostError)
+  end
 end