logtail is a log tailing utility.

1. Features

• tailing command output
• support watch files under directory/sub-directories
• support (dynamically) multiple commands tailing
• support websocket tailing
• support log matching filter
• support transfer log to console/file/webhook (include dingtalk)

2. Architecture

3. Usage

3.2. install logtail

go install github.com/vogo/logtail@master

3.2. StartLoop logtail server using config file

logtail -file <config-file>

config file examples.

3.3. StartLoop logtail server and config using webapi

usage: logtail -port=<port>

# start at port 54321
logtail -port=54321

Then config using web api from web page http://<server-ip>:<port>/manage.

And you can browse http://<server-ip>:<port> to list all tailing logs.

4. log format

You can config log format globally, or config it for a server.

The config prefix of the format is the wildcard of the prefix of a new log record, logtail will check whether a new line is the StartLoop of a new log record, or one of the following lines.

The wildcard does NOT support '*' for none or many chars, it supports the following tag:

• '?' as one byte char;
• '~' as one alphabet char;
• '!' as one number char;
• other chars must exact match.

example:

{
    "default_format":{
      "prefix": "!!!!-!!-!!"  # global format config, Matches 2020-12-12
    },
    "servers": [
        {
          "name": "app1",
          "command": "tail -f /logs/app/app1.log",
          "format":{
            "prefix": "!!!!-!!-!!" # server format config, Matches 2020-12-12
          }
        }
    ]
}

4. command examples

The following are some useful commands which can be used in logtail.

# tail log file
tail -f /usr/local/myapp/myapp.log

# k8s: find and tail logs for the single pod of myapp
kubectl logs --tail 10 -f $(kubectl get pods --selector=app=myapp -o jsonpath='{.items[*].metadata.name}')

# k8s: find and tail logs for the myapp deployment (multiple pods)
kubectl logs --tail 10 -f deployment/$(kubectl get deployments --selector=project-name=myapp -o jsonpath='{.items[*].metadata.name}')

# k8s: find and tail logs for the latest version of the myapp deployment (single pod)
s=$(kubectl get deployments --selector=project-name=myapp -o jsonpath='{.items[*].metadata.name}');s=${s##* };kubectl logs --tail 10 -f deployment/$s

# k8s: find and tail logs for the latest version of the myapp deployment (multiple pods)
app=$(kubectl get deployments --selector=project-name=myapp -o jsonpath='{.items[*].metadata.name}');app=${app##* };pods=$(kubectl get pods --selector=app=$app -o jsonpath='{.items[*].metadata.name}');cmd='';for pod in $pods; do cmd=$cmd'kubectl logs --tail 2 -f pod/'$pod$'\n'; done;cmd=${cmd::-1}; echo "$cmd"