Prevent Internal Server Error with Symfony 2 / Monolog on failed gelf connection

I'm trying to stream logs from a symfony 2 app to a graylog 2 server using the gelf format.

My monolog configuration looks as follows:

monolog:
    handlers:
          # --- 8< ---
          # ...
          # --- >8 --- 
          graylog:
              type: gelf
              publisher:
                  hostname: my-graylog-server.com
                  port: 12201
              level: debug
              formatter: app.gelf_formatter

When the graylog server is not available, I get (understandably) a connection refused error

[2017-07-28 16:03:25] app.ERROR: Failed to write to socket: fwrite(): send of 153 bytes failed with errno=111 Connection refused (8) [] []

which results in an internal server error (500 response code to the request causing the log).

What's the best way to catch this error? Having an error log is resonable, but I don't want my requests to error when the external log processing server is not available?