I have a server that is the host OS for multiple docker containers. Each of the containers contains an application that is creating logs. I want these logs to be sent to a single place by using the syslog daemon, and then I want filebeat to transmit this data to another server. Is it possible to install filebeat on the HOST OS (without making another container for filebeat), and make the containers applications' log data be collected by the syslog daemon and then consolidated in /var/log on the host OS? Thanks.
You need to share a volume with every container in order to get your logs in the host filesystem.
Then, you can install filebeat on the host and forward the logs where you want, as they were "standard" log files.
Please be aware that usually docker containers do not write they logs to real log files, but to stdout. That means that you'll probably need custom images in order to fix this logging problem.
Related
I’m looking for the appropriate way to monitor applicative logs produced by nginx, tomcat, springboot embedded in docker with filebeat and ELK.
In the container strategy, a container should be used for only one purpose.
One nginx per container and one tomcat per container, meaning we can’t have an additional filebeat within a nginx or tomcat container.
Over what I have read over Internet, we could have the following setup:
a volume dedicated for storing logs
a nginx container which mount the dedicated logs volume
a tomcat / springboot container which mount the dedicated logs volume
a filebeat container also mounting the dedicated logs volume
This works fine but when it comes to scale out nginx and springboot container, it is a little bit more complex for me.
Which pattern should I use to push my logs using filebeat to logstash if I have the following configuration:
several nginx containers in load balancing with the same configuration (logs configuration is the same: same path)
several springboot rest api containers behing nginx containers with the same configuration (logs configuration is the same:same path)
Should I create one volume by set of nginx + springboot rest api and add a filebeat container ?
Should I create a global log volume shared by all my containers and have a different log filename by container
(having the name of the container in the filename of the logs?) and having only one filebeat container ?
In the second proposal, how to scale filebeat ?
Is there another way to do that ?
Many thanks for your help.
The easiest thing to do, if you can manage it, is to set each container process to log to its own stdout (you might be able to specify /dev/stdout or /proc/1/fd/1 as a log file). For example, the Docker Hub nginx Dockerfile specifies
RUN ln -sf /dev/stdout /var/log/nginx/access.log \
&& ln -sf /dev/stderr /var/log/nginx/error.log
so the ordinary nginx logs become the container logs. Once you do that, you can plug in the filebeat container input to read those logs and process them. You could also see them from outside the container with docker logs, they are the same logs.
What if you have to log to the filesystem? Or there are multiple separate log streams you want to be able to collect?
If the number of containers is variable, but you have good control over their configuration, then I'd probably set up a single global log volume as you describe and use the filebeat log input to read every log file in that directory tree.
If the number of containers is fixed, then you can set up a volume per container and mount it in each container's "usual" log storage location. Then mount all of those directories into the filebeat container. The obvious problem here is that if you do start or stop a container, you'll need to restart the log manager for the added/removed volume.
If you're actually on Kubernetes, there are two more possibilities. If you're trying to collect container logs out of the filesystem, you need to run a copy of filebeat on every node; a DaemonSet can manage this for you. A Kubernetes pod can also run multiple containers, so your other option is to set up pods with both an application container and a filebeat "sidecar" container that ships the logs off. Set up the pod with an emptyDir volume to hold the logs, and mount it into both containers. A template system like Helm can help you write the pod specifications without repeating the logging sidecar setup over and over.
I am using gelf as log driver for my docker container. In log options i provided udp endpoint.
Now when i start the container, everything is working as expected.
My question is, if it is possible to see the container logs in the host where it is running(not at UDP endpoint)?
This depends on Docker version.
Docker 20.10 and up introduces “dual logging”, which uses a local buffer that allows you to use the docker logs command for any logging driver.
If you are talking about seeing the logs via docker logs command on the machine running the docker containers, its not possible to do so when using other logging drivers.
See limitations of logging drivers.
If you know where the log is at inside the container, a work around would be to write a script which copies the log file from the container and displays it, or maybe just exec's into the container and displays it. But I really wouldn't recommend that.
Something like:
#!/bin/bash
docker cp mycontainer:/var/log/mylog.log $(pwd)/logs/mylog.log
tail -f $(pwd)/logs/mylog.log
I have one question, Is there any way to ship the logs of each container where the log files are located inside the containers. Actually, the current flow will help to ship the log files which is located in the default path(var/lib/docker/containers//.log). I want to customize the filebeat.yaml to ship the logs from each container to logstash instead of the default path.
If you can set your containers to log to stdout rather than to files, it looks like filebeat has an autodiscover mode which will capture the docker logs of every container.
Another common setup in an ELK world is to configure logstash on your host, and set up Docker's logging options to send all output on containers' stdout into logstash. This makes docker logs not work, but all of your log output is available via Kibana.
If your container processes always write to log files, you can use the docker run -v option or the Docker Compose volumes: option to mount a host directory on to an individual container's /var/log directory. Then the log files will be visible on the host, and you can use whatever file-based collector to capture them. This is in the realm of routine changes that will require you to stop and delete your existing containers before starting them with different options.
I am trying to run syslog inside Docker so that it has access to DNS configuration for the container. Is it possible run syslog inside Docker and expose that to the host as host's syslog daemon?
Yes. I'm doing this at the moment, because I've got a containerised ELK (Elasticsearch/Logstash/Kibana).
My logstash runs a listener on port 514 for syslog traffic* which it forwards to ELK.
Well, more correctly - I'm running a haproxy instance, that I'm redirecting using confd and etcd to wherever my syslog container is, but the principle stands.
My hosts have
*.* ##localhost
in their rsyslog.conf
And it works nicely. (and I can also log from my containers to this syslogd)
I think this a bit old but it can help others!
I think the best way is to use docker driver to send logs to syslog instead of running syslog inside.
One of the best practices in docker is to run only one process inside the container.
If you would like to have one docker running syslog inside and forward all logs to this container from other containers this will be good idea, because you will separate concerns and also you can scale the log container.
Here is a container that do that: enter link description here
When we run the same process in docker and in host system, how it differentiates one from the other, from the perspective of audit logs?
Can I view the process running in docker in host system?
You would not run the same process (same pid) in docker and in host, since the purpose of a container is to provide isolation (both processes and filesystem)
I mentioned in your previous question "Docker Namespace in kernel level" that the pid of a process run in a container could be made visible from the host.
But in term of audit log, you can configure logging drivers in order to follow only containers, and ignore processes running directly on host.
For instance, in this article, Mark configures rsyslog to isolate the Docker logs into their own file.
To do this create /etc/rsyslog.d/10-docker.conf and copy the following content into the file using your favorite text editor.
# Docker logging
daemon.* {
/var/log/docker.log
stop
}
In summary this will write all logs for the daemon category to /var/log/docker.log then stop processing that log entry so it isn’t written to the systems default syslog file.
That should be enough to clearly differentiate the host processes logs (in regular syslog) from the ones running in containers (in /var/log/docker.log)
Update May 2016: issue 10163 and --pid=container:id is closed by PR 22481 for docker 1.12, allowing to join another container's PID namespace.