Logging

Basic logging

The most basic form of logging in uWSGI is writing requests, errors, and informational messages to stdout/stderr. This happens in the default configuration. The most basic form of log redirection is the --logto / --logto2 / --daemonize options which allow you to redirect logs to files.

Basic logging to files

To log to files instead of stdout/stderr, use --logto, or to simultaneously daemonize uWSGI, --daemonize.

./uwsgi -s :3031 -w simple_app --daemonize /tmp/mylog.log
./uwsgi -s :3031 -w simple_app --logto /tmp/mylog.log
# logto2 only opens the log file after privileges have been dropped to the specified uid/gid.
./uwsgi -s :3031 -w simple_app --uid 1001 --gid 1002 --logto2 /tmp/mylog.log

Basic logging (connected UDP mode)

With UDP logging you can centralize cluster logging or redirect the persistence of logs to another machine to offload disk I/O. UDP logging works in both daemonized and interactive modes. UDP logging operaties in connected-socket mode, so the UDP server must be available before uWSGI starts. For a more raw approach (working in unconnected mode) see the section on socket logging.

To enable connected UDP mode pass the address of a UDP server to the --daemonize/--logto option:

./uwsgi -s :3031 -w simple_app --daemonize 192.168.0.100:1717
./uwsgi -s :3031 -w simple_app --logto 192.168.0.100:1717

This will redirect all the stdout/stderr data to the UDP socket on 192.168.0.100, port 1717. Now you need an UDP server that will manage your UDP messages. You could use netcat, or even uWSGI:

nc -u -p 1717 -s 192.168.0.100 -l
./uwsgi --udp 192.168.0.100:1717

The second way is a bit more useful as it will print the source (ip:port) of every message. In case of multiple uWSGI server logging on the same UDP server it will allow you to recognize one server from another. Naturally you can write your own apps to manage/filter/save the logs received via udp.

Pluggable loggers

uWSGI also supports pluggable loggers, which allow you more flexibility on where and what to log. Depending on the configuration of your uWSGI build, some loggers may or may not be available. Some may require to be loaded as plugins. To find out what plugins are available in your build, invoke uWSGI with --logger-list. To set up a pluggable logger, use the --logger or --req-logger options. --logger will set up a logger for every message while --req-logger will set up a logger for request information messages.

This is the syntax:

--logger <plugin>[:options]
--logger "<name> <plugin>[:options]" # The quotes are only required on the command line -- config files don't use them

You may set up as many loggers as you like. Named plugins are used for log routing. A very simple example of split request/error logging using plain text files follows.

[uwsgi]
req-logger = file:/tmp/reqlog
logger = file:/tmp/errlog

Log routing

By default all log lines are sent to all declared loggers. If this is not what you want, you can use --log-route (and --log-req-route for request loggers) to specify a regular expression to route certain log messages to different destinations.

For instance:

[uwsgi]
logger = mylogger1 syslog
logger = theredisone redislog:127.0.0.1:6269
logger = theredistwo redislog:127.0.0.1:6270
logger = file:/tmp/foobar # This logger will log everything else, as it's not named
logger = internalservererror file:/tmp/errors
# ...
log-route = internalservererror (HTTP/1.\d 500)
log-route = mylogger1 uWSGI listen queue of socket .* full

This will log each 500 level error to /tmp/errors, while listen queue full errors will end up in /tmp/foobar. This is somewhat similar to the The uWSGI alarm subsystem (from 1.3), though alarms are usually heavier and should only be used for critical situations.

Logging to files

logfile plugin – embedded by default.

Logging to sockets

logsocket plugin – embedded by default.

You can log to an unconnected UNIX or UDP socket using --logger socket:... (or --log-socket ...).

uwsgi --socket :3031 --logger socket:/tmp/uwsgi.logsock

will send log entries to the Unix socket /tmp/uwsgi.logsock.

uwsgi --socket :3031 --logger socket:192.168.173.19:5050

will send log datagrams to the UDP address 192.168.173.19 on port 5050. You may also multicast logs to multiple log servers by passing the multicast address:

uwsgi --socket :3031 --logger socket:225.1.1.1:1717

Logging to syslog

syslog plugin – embedded by default

The syslog plugin routes logs to Unix standard syslog. You may pass an optional ID to send and the “facility” for the log entry.

uwsgi --socket :3031 --logger syslog:uwsgi1234

or

uwsgi --socket :3031 --logger syslog:uwsgi1234,local6

to send to the local6 facility

Logging to remote syslog

rsyslog plugin – embedded by default

The rsyslog plugin routes logs to Unix standard syslog residing on a remote server. In addtition to the address+port of the remote syslog server, you may pass an optional ID to send as the “facility” parameter for the log entry.

uwsgi --socket :3031 --logger rsyslog:12.34.56.78:12345,uwsgi1234

Redis logger

redislog plugin – embedded by default.

By default the redislog plugin will ‘publish’ each logline to a redis pub/sub queue. The logger plugin syntax is:

--logger redislog[:<host>,<command>,<prefix>]

By default host is mapped to 127.0.0.1:6379, command is mapped to “publish uwsgi” and prefix is empty. To publish to a queue called foobar, use redislog:127.0.0.1:6379,publish foobar. Redis logging is not limited to pub/sub. You could for instance push items into a list, as in the next example.

--logger redislog:/tmp/redis.sock,rpush foo,example.com

As error situations could cause the master to block while writing a log line to a remote server, it’s a good idea to use --threaded-logger to offload log writes to a secondary thread.

MongoDB logger

mongodblog plugin – embedded by default.

The logger syntax for MongoDB logging (mongodblog) is

--logger mongodblog[:<host>,<collection>,<node>]

Where host is the address of the MongoDB instance (default 127.0.0.1:27017), collection names the collection to write log lines into (default uwsgi.logs) and node is an identification string for the instance sending logs (default: server hostname).

--logger mongodblog

Will run the logger with default values, while

--logger mongodblog:127.0.0.1:9090,foo.bar

Will write logs to the mongodb server 127.0.0.1:9090 in the collection foo.bar using the default node name. As with the Redis logger, offloading log writes to a dedicated thread is a good choice.

[uwsgi]
threaded-logger = true
logger = mongodblog:127.0.0.1:27017,uwsgi.logs_of_foobar
# As usual, you could have multiple loggers:
# logger = mongodblog:192.168.173.22:27017,uwsgi.logs_of_foobar
socket = :3031

ZeroMQ logging

As with UDP logging you can centralize/distribute logging via ZeroMQ. Build your logger daemon using a ZMQ_PULL socket:

import zmq

ctx = zmq.Context()

puller = ctx.socket(zmq.PULL)
puller.bind("tcp://192.168.173.18:9191")

while True:
    message = puller.recv()
    print message,

Now run your uWSGI server:

uwsgi --logger zeromq:tcp://192.168.173.18:9191 --socket :3031 --module werkzeug.testapp:test_app

(--log-zeromq is an alias for this logger.)

Crypto logger (plugin)

If you host your applications on cloud services without persistent storage you may want to send your logs to external systems. However logs often contain sensitive information that should not be transferred in clear. The logcrypto plugin logger attempts to solve this issue by encrypting each log packet before sending it over UDP to a server able to decrypt it. The next example will send each log packet to a UDP server available at 192.168.173.22:1717 encrypting the text with the secret key ciaociao with Blowfish in CBC mode.

uwsgi --plugin logcrypto --logger crypto:addr=192.168.173.22:1717,algo=bf-cbc,secret=ciaociao -M -p 4 -s :3031

An example server is available at https://github.com/unbit/uwsgi/blob/master/contrib/cryptologger.rb

Graylog2 logger (plugin)

graylog2 plugin – not compiled by default.

This plugin will send logs to a Graylog2 server in Graylog2’s native GELF format.

uwsgi --plugin graylog2 --logger graylog2:127.0.0.1:1234,dsfargeg

Systemd logger (plugin)

systemd_logger plugin – not compiled by default.

This plugin will write log entries into the Systemd journal.

uwsgi --plugin systemd_logger --logger systemd

Writing your own logger plugins

This plugin, foolog.c will write your messages in the file specified with –logto/–daemonize with a simple prefix using vector IO.

#include <uwsgi.h>

ssize_t uwsgi_foolog_logger(struct uwsgi_logger *ul, char *message, size_t len) {

        struct iovec iov[2];

        iov[0].iov_base = "[foo] ";
        iov[0].iov_len = 6;

        iov[1].iov_base = message;
        iov[1].iov_len = len;

        return writev(uwsgi.original_log_fd, iov, 2);
}

void uwsgi_foolog_register() {
        uwsgi_register_logger("syslog", uwsgi_syslog_logger);
}

struct uwsgi_plugin foolog_plugin = {
    .name = "foolog",
    .on_load = uwsgi_foolog_register,
};