Allow for exception instances to get serialized in JSON logging

logstash-core/lib/logstash/patches.rb

@@ -3,3 +3,4 @@ require "logstash/patches/bugfix_jruby_2558"
 require "logstash/patches/cabin"
 require "logstash/patches/profile_require_calls"
 require "logstash/patches/stronger_openssl_defaults"
+require "logstash/patches/exception_to_json"

logstash-core/lib/logstash/patches/exception_to_json.rb

@@ -0,0 +1,5 @@
+class Exception
+  def to_json
+    {"exception_name" => self.class.name, "message" => message}
+  end
+end

logstash-core/spec/logstash/patches_spec.rb

@@ -2,6 +2,7 @@
 require "socket"
 require "logstash/patches"
 require "flores/pki"
+require "logstash/json"
 
 describe "OpenSSL defaults" do
   subject { OpenSSL::SSL::SSLContext.new }
@@ -88,3 +89,13 @@ describe "OpenSSL defaults" do
     end
   end
 end
+
+describe "exceptions used json logging hashes" do
+  let(:exception) { ArgumentError.new("so you want an argument, huh?") }
+  let(:result) { [] }
+
+  it "should not raise errors" do
+    expect { result << LogStash::Json.dump({"error" => exception}) }.not_to raise_error
+    expect(result[0]).to match(/ArgumentError.*so you want an argument/)
+  end
+end