I'm running uwsgi around a Python Flask webapp with these options (among others) to get JSON-encoded log records on stdout:

fmt=$'{"timestamp": "${strftime:%FT%TZ}", "level": "DEBUG", "name": "uwsgi", "message": "${msg}"}\n'uwsgi --env="TZ=UTC" --log-encoder="json ${fmt}" --logformat="%(status) [%(msecs)ms] %(method) %(uri)"

This nicely encodes the stdout from uwsgi but unfortunately also encodes the logging from my application, which is already in JSON format so I get things like:

{"timestamp": "2017-10-02T22:48:11Z", "level": "DEBUG", "name": "uwsgi", "message": "spawned uWSGI http 1 (pid: 75298)"}
{"timestamp": "2017-10-02T22:48:15Z", "level": "DEBUG", "name": "uwsgi", "message": "{\"timestamp\": \"2017-10-02T22:48:15.200Z\", \"message\": \"Descriptor requested\", \"request\": \"c6b08680-a7c3-11e7-9495-186590cba8eb\", \"name\": \"myapp.main\", \"level\": \"INFO\"}"}
{"timestamp": "2017-10-02T22:48:15Z", "level": "DEBUG", "name": "uwsgi", "message": "200 [11ms] GET /descriptor.json"}

The middle record has been wrapped in the same JSON encoding as other output from uwsgi.

How do I avoid the output from my Flask application being encoded but keep encoding of other output from uwsgi itself?

I've tried various combinations of --log-encoder and --log-req-encoder but the latter seems to encode nothing. The docs are not very clear on the distinction between the two options.

In the end I had to remove --log-encoder and pass stdout (and stderr) through a process that wrapped output in JSON unless already encoded as JSON.

function log_json() { python -u -c "import sysimport jsonimport datetimelog = dict(name='uwsgi', level='$1')line = sys.stdin.readline()while line:line = line.strip()if line.startswith('{') and line.endswith('}'):print(line)elif line:log['timestamp'] = datetime.datetime.utcnow().isoformat() + 'Z'log['message'] = lineprint(json.dumps(log))line = sys.stdin.readline()
"; }{ uwsgi ... 2>&1 1>&3 3>&- | log_json ERROR; } 3>&1 1>&2 | log_json INFO

If you just want to encode request logging, add --logger-req=stdio option to get --log-req-encoder to encode request logging properly.