Bug Fix: Fix ability to change log level via the API

The ability to change the log level as described at https://www.elastic.co/guide/en/logstash/current/logging.html#_logging_apis appears to no longer work. The root cause of this issue is that log4j2 context we initialize is different from the log4j2 context that we are setting via the API. The fix here is to mirror the functionality of org.apache.logging.log4j.core.config.Configurator.setLevel Java method, but instead use the logging_context initialized in our code via JRuby.

Fixes #7277

Fixes #7321

logstash-core/lib/logstash/logging/logger.rb

@@ -7,6 +7,7 @@ module LogStash
     java_import org.apache.logging.log4j.LogManager
     java_import org.apache.logging.log4j.core.config.Configurator
     java_import org.apache.logging.log4j.core.config.DefaultConfiguration
+    java_import org.apache.logging.log4j.core.config.LoggerConfig
 
     class Logger
       @@config_mutex = Mutex.new
@@ -65,7 +66,7 @@ module LogStash
       end
 
       def self.configure_logging(level, path = LogManager::ROOT_LOGGER_NAME)
-        @@config_mutex.synchronize { Configurator.setLevel(path, Level.valueOf(level)) }
+        @@config_mutex.synchronize { set_level(level, path) }
       rescue Exception => e
         raise ArgumentError, "invalid level[#{level}] for logger[#{path}]"
       end
@@ -90,6 +91,30 @@ module LogStash
       def self.get_logging_context
         return @@logging_context
       end
+
+      # Clone of org.apache.logging.log4j.core.config.Configurator.setLevel(), but using initialized @@logging_context
+      def self.set_level(_level, path)
+        configuration = @@logging_context.getConfiguration()
+        level = Level.valueOf(_level)
+        if path.nil? || path.strip.empty?
+          root_logger = configuration.getRootLogger()
+          if root_logger.getLevel() != level
+            root_logger.setLevel(level)
+            @@logging_context.updateLoggers()
+          end
+        else
+          package_logger = configuration.getLoggerConfig(path)
+          if package_logger.name != path #no package logger found
+            configuration.addLogger(path, LoggerConfig.new(path, level, true))
+            @@logging_context.updateLoggers()
+          elsif package_logger.getLevel() != level
+            package_logger.setLevel(level)
+            @@logging_context.updateLoggers()
+          end
+        end
+      end
+
+      private_class_method :set_level
     end
 
     class SlowLogger

qa/integration/services/monitoring_api.rb

@@ -33,4 +33,13 @@ class MonitoringAPI
     JSON.parse(resp)
   end
 
+  def logging_get
+    resp = Manticore.get("http://localhost:9600/_node/logging").body
+    JSON.parse(resp)
+  end
+
+  def logging_put(json_body)
+    resp = Manticore.put("http://localhost:9600/_node/logging", {headers: {"Content-Type" => "application/json"}, body: json_body }).body
+    JSON.parse(resp)
+  end
 end

qa/integration/specs/monitoring_api_spec.rb

@@ -77,4 +77,63 @@ describe "Test Monitoring API" do
       end
     end
   end
+
+  it "can configure logging" do
+    logstash_service = @fixture.get_service("logstash")
+    logstash_service.start_with_stdin
+    logstash_service.wait_for_logstash
+
+    Stud.try(max_retry.times, [StandardError, RSpec::Expectations::ExpectationNotMetError]) do
+      # monitoring api can fail if the subsystem isn't ready
+      result = logstash_service.monitoring_api.logging_get rescue nil
+      expect(result).not_to be_nil
+      expect(result["loggers"].size).to be > 0
+      #default
+      logging_get_assert logstash_service, "INFO", "TRACE"
+
+      #root logger - does not apply to logger.slowlog
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger." => "WARN"}.to_json)
+      logging_get_assert logstash_service, "WARN", "TRACE"
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger." => "INFO"}.to_json)
+      logging_get_assert logstash_service, "INFO", "TRACE"
+
+      #package logger 
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger.logstash.agent" => "DEBUG"}.to_json)
+      expect(logstash_service.monitoring_api.logging_get["loggers"]["logstash.agent"]).to eq ("DEBUG")
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger.logstash.agent" => "INFO"}.to_json)
+      logging_get_assert logstash_service, "INFO", "TRACE"
+
+      #parent package loggers
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger.logstash" => "ERROR"}.to_json)
+      logging_put_assert logstash_service.monitoring_api.logging_put({"logger.slowlog" => "ERROR"}.to_json)
+
+      result = logstash_service.monitoring_api.logging_get
+      result["loggers"].each do | k, v |
+        #since we explicitly set the logstash.agent logger above, the parent logger will not take precedence
+        if k.eql? "logstash.agent"
+          expect(v).to eq("INFO")
+        else
+          expect(v).to eq("ERROR")
+        end
+      end
+    end
+  end
+
+  private
+
+  def logging_get_assert(logstash_service, logstash_level, slowlog_level)
+    result = logstash_service.monitoring_api.logging_get
+    result["loggers"].each do | k, v |
+      if k.start_with? "logstash"
+        expect(v).to eq(logstash_level)
+      elsif k.start_with? "slowlog"
+        expect(v).to eq(slowlog_level)
+      end
+    end
+  end
+
+  def logging_put_assert(result)
+    expect(result["acknowledged"]).to be(true)
+  end
+
 end