sidecar

Tailing sidecar container image

tailing sidecar container image is a an image which can be used to manually extend Pods by streaming sidecar containers.

Getting Started

To understand benefits of using tailing sidecar see example below.

Extend Pod by adding tailing sidecars

Assuming that container writes logs to two different files and Pod has this specification:

apiVersion: v1
kind: Pod
metadata:
  name: example-with-tailling-sidecars
spec:
  containers:
  - name: count
    image: busybox
    args:
    - /bin/sh
    - -c
    - >
      i=0;
      while true;
      do
        echo "example1: $i $(date)" >> /var/log/example1.log;
        echo "example2: $i $(date)" >> /var/log/example2.log;
        i=$((i+1));
        sleep 1;
      done
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  volumes:
  - name: varlog
    emptyDir: {}

Pod can be extended by adding tailing sidecar containers for easier log access:

apiVersion: v1
kind: Pod
metadata:
  name: example-with-tailling-sidecars
spec:
  containers:
  - name: count
    image: busybox
    args:
    - /bin/sh
    - -c
    - >
      i=0;
      while true;
      do
        echo "example1: $i $(date)" >> /var/log/example1.log;
        echo "example2: $i $(date)" >> /var/log/example2.log;
        i=$((i+1));
        sleep 1;
      done
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  - name: sidecar1
    image: ghcr.io/sumologic/tailing-sidecar:latest
    env:
    - name: PATH_TO_TAIL
      value: /var/log/example1.log
    - name: LOG_LEVEL
      value: warning
    volumeMounts:
    - name: varlog
      mountPath: /var/log
    - name: volume-sidecar1
      mountPath: /tailing-sidecar/var
  - name: sidecar2
    image: ghcr.io/sumologic/tailing-sidecar:latest
    env:
    - name: PATH_TO_TAIL
      value: /var/log/example2.log
    - name: LOG_LEVEL
      value: warning
    volumeMounts:
    - name: varlog
      mountPath: /var/log
    - name: volume-sidecar2
      mountPath: /tailing-sidecar/var
  volumes:
  - name: varlog
    emptyDir: {}
  - name: volume-sidecar1
    hostPath:
      path: /var/log/sidecar1
      type: DirectoryOrCreate
  - name: volume-sidecar2
    hostPath:
      path: /var/log/sidecar2
      type: DirectoryOrCreate

Notice that tailing sidecar containers are configured through two environmental variables:

• PATH_TO_TAIL - pattern specifying a log file or multiple ones through the use of common wildcards, multiple patterns separated by commas are also allowed
• LOG_LEVEL - verbosity level, by default 'warning' is set, allowed values: error, warning, info, debug, trace

Try it!

kubectl apply -f sidecar/examples/pod_with_tailing_sidecars.yaml

And check logs:

$ kubectl logs example-with-tailling-sidecars sidecar1
example1: 0 Wed Jan 27 11:59:28 UTC 2021
example1: 1 Wed Jan 27 11:59:29 UTC 2021
example1: 2 Wed Jan 27 11:59:30 UTC 2021
example1: 3 Wed Jan 27 11:59:31 UTC 2021
...

$ kubectl logs example-with-tailling-sidecars sidecar2
example2: 0 Wed Jan 27 11:59:28 UTC 2021
example2: 1 Wed Jan 27 11:59:29 UTC 2021
example2: 2 Wed Jan 27 11:59:30 UTC 2021
example2: 3 Wed Jan 27 11:59:31 UTC 2021
...

Run tailing sidecar in Docker container

To run tailing sidecar in Docker container define following variables:

• DIR_TO_TAIL - path to directory with files to read
• FLUENT_BIT_DB_DIR - path to directory where Fluent Bit database will be created, Fluent Bit uses database to track monitored files and offsets, for details please see tail plugin documentation
• FILES_PATTERN - pattern to match files in directory specified as DIR_TO_TAIL
• TAILING_SIDECAR_IMAGE - tailing sidecar Docker image
• LOG_LEVEL - verbosity level, by default 'warning' is set, allowed values: error, warning, info, debug, trace

e.g.

export DIR_TO_TAIL="$PWD/examples"
export FLUENT_BIT_DB_DIR="$PWD/var"
export FILES_PATTERN="*.log"
export TAILING_SIDECAR_IMAGE="ghcr.io/sumologic/tailing-sidecar:latest"
export LOG_LEVEL="warning"

And run tailing sidecar in Docker container:

docker run --rm -it \
    -v ${DIR_TO_TAIL}:/tmp/host \
    -v ${FLUENT_BIT_DB_DIR}:/tailing-sidecar/var \
    --env "PATH_TO_TAIL=/tmp/host/${FILES_PATTERN}" \
    --env "LOG_LEVEL=${LOG_LEVEL}" ${TAILING_SIDECAR_IMAGE}

Build and run tailing sidecar in Docker container

To build and run Docker container with tailing sidecar to tail files in $PWD/examples which match pattern *.log and save Fluent Bit database in $PWD/var:

make run \
    TAG=sidecar:dev \
    DIR_TO_TAIL="$PWD/examples" \
    FILES_PATTERN="*.log" \
    FLUENT_BIT_DB_DIR="$PWD/var" \
    LOG_LEVEL="warning"

Build and push tailing sidecar to Docker registry

To build Docker image with tailing sidecar:

make build TAG=<DOCKER_IMAGE_TAG>

e.g.

make build TAG=localhost:32000/sumologic/tailing-sidecar:latest

To push Docker image to container registry:

make push TAG=<DOCKER_IMAGE_TAG>

e.g.

make push TAG=localhost:32000/sumologic/tailing-sidecar:latest

Testing in Vagrant environment

Prerequisites

Please install the following:

• VirtualBox
• Vagrant
• vagrant-disksize plugin

Setting up

Start and provision the Vagrant environment:

vagrant up

Connect to virtual machine:

vagrant ssh

Build and run tailing sidecar

Build and push docker image to local container registry:

/tailing-sidecar/sidecar/Makefile

Run example Pod:

kubectl apply -f /tailing-sidecar/sidecar/examples/pod_with_tailing_sidecars.yaml