Local syslog support

[gtmtech]

It would be great if logspout could ship logs to the local host syslog, rather than just remote syslog, without having to have a UDP or TCP listener on the host syslog.

I know docker 1.6 kind of introduces this anyway with --log-driver, but its missing many options, not very configurable until docker 1.8 --log-opt, and it would be great if logspout could do this anyway.

[brianz]

I'm also very interested in this. Are there currently any tricks or work arounds to get logspout to send to the Docker host's syslog?

[kassanmoor]

Also interested on this, let me know is there are a workaround without touching the syslog config

[freerobby]

Hey folks, not sure if this is still relevant to you, but a pretty simple work-around is to run a second docker container that uses socat to listen on a UDP port and forward it to the /dev/log datagram socket. For example:

docker pull alpine/socat
docker run --volume=/dev/log:/dev/log alpine/socat UDP4-LISTEN:514,fork UNIX-CLIENT:/dev/log

Followed by: docker run --rm -P --name="logspout" --volume=/var/run/docker.sock:/var/run/docker.sock --volume=/dev/log:/dev/log gliderlabs/logspout syslog://172.17.0.2:514

where 172.17.0.2 is the IP address of the socat container. Alternatively, you can forward port 514 from the socat container to the host and then use the host IP instead of the container IP.

You'll likely want to add an "always" restart policy to the socat container to be safe.

[dickerpulli]

@michaelshobbs @progrium What about this request. Is there any progess? Will there be a unix (unixgram) support for syslog in the near future?

[michaelshobbs]

I'm not opposed to this functionality and would certainly accept a well tested and documented PR implementing this

[allenyllee]

I found a blog: "Log management for docker made easy (EN)", as it says, we can use logspout and syslog-ng to achieve local central log management.

Below is the docker-compose.yml and syslog-ng.conf files that the blog use in this setup. When putting these files in the same folder, and execute docker-compose up -d, then the logspout and syslogng container will spin up, and aggregate all container's log into /logs folder.

docker-compose.yml

version: '3'
services:
  logspout:
    image: gliderlabs/logspout:latest
    restart: always
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"
    command: syslog+udp://syslogng:514
  syslogng:
    image: balabit/syslog-ng:latest
    restart: always
    command: -F --no-caps
    volumes:
      - "/logs/:/var/log/syslogng/"
      - "./syslog-ng.conf:/etc/syslog-ng/syslog-ng.conf"

syslog-ng.conf

@version: 3.19
@include "scl.conf"
source s_network {
  default-network-drivers();
};
destination d_local {
  file("/var/log/syslogng/${PROGRAM}.${HOST}-${YEAR}.${MONTH}.${DAY}.log");
};
log {
  source(s_network);
  destination(d_local);
};

But as the blog author says, there are no auto log rotation/flushing, you may setup a cron job to achieve this:

1. create a file named rotate_and_flush.sh as below

   rotate_and_flush.sh

   # to compress 2 days old logs
   find /var/log/syslogng/ -name "*.log" -daystart -ctime +2 -type f -exec gzip {} \;
   # to remove 14 days old logs
   find /var/log/syslogng/ -name "*.gz" -daystart -ctime +14 -type f -exec rm {} \; 

2. adding a volumes entry - "./rotate_and_flush.sh:/etc/cron.daily/rotate_and_flush.sh" at syslogng container to mount rotate_and_flush.sh into container's /etc/cron.hourly/, which will execute that script hourly:

   docker-compose.yml

   version: '3'
   services:
     logspout:
       image: gliderlabs/logspout:latest
       restart: always
       volumes:
         - "/var/run/docker.sock:/var/run/docker.sock:ro"
       command: syslog+udp://syslogng:514
     syslogng:
       image: balabit/syslog-ng:latest
       restart: always
       command: -F --no-caps
       volumes:
         - "/logs/:/var/log/syslogng/"
         - "./syslog-ng.conf:/etc/syslog-ng/syslog-ng.conf"
         - "./rotate_and_flush.sh:/etc/cron.daily/rotate_and_flush.sh"

[allenyllee]

I have created a repo to do the above things and modified to use logrotate to rotate log files. see: https://github.com/allenyllee/locallogm