auger: A Go repository from divanodestiny

Auger

Directly access data objects stored in etcd by kubernetes.

Encodes and decodes Kubernetes objects from the binary storage encoding used to store data to etcd. Supports data conversion to YAML, JSON and Protobuf.

Automatically determines if etcd data is stored in JSON (kubernetes 1.5 and earlier) or binary (kubernetes 1.6 and newer) and decodes accordingly.

Why?

In earlier versions of kubernetes, data written to etcd was stored as JSON and could easily be inspected or manipulated using standard tools such as etcdctl. In kubernetes 1.6+, for efficiency reasons, much of the data is now stored in a binary storage representation, and is non-trivial to decode-- it contains a enveloped payload that must be unpacked, type resolved and decoded.

This tool provides kubernetes developers and cluster operators with simple way to access the binary storage data via YAML and JSON.

Installation

Check out and build:

git clone https://github.com/jpbetz/auger
cd auger
make release

Run:

build/auger -h

Use cases

Access data via etcdctl

A kubernetes developer or cluster operator needs to inspect the data actually stored to etcd for a particular kubernetes object.

E.g., decode a pod from etcd v3, where <pod-name> is the name of one of your pods:

ETCDCTL_API=3 etcdctl get /registry/pods/default/<pod-name> | auger decode
> apiVersion: v1
> kind: Pod
> metadata:
>   annotations: ...
>   creationTimestamp: 2017-06-27T16:35:34Z
> ...

Modify data via etcdctl

A kubernetes developer or etcd developer needs to modify state of an object stored in etcd.

E.g. Write an updated pod to etcd v3:

cat updated-pod.yaml | auger encode | ETCDCTL_API=3 etcdctl put /registry/pods/default/<pod-name>

Access data directly from db file

A cluster operator, kubernetes developer or etcd developer is needs to inspect etcd data without starting etcd. In extreme cases, it may not be possible to start etcd and inspecting the data may help a etcd developer understand what state it is in.

E.g. find an etcd value by it's key and extract it from a boltdb file:

auger extract -f <boltdb-file> -k /registry/pods/default/<pod-name>
> apiVersion: v1
> kind: Pod
> metadata:
>   annotations: ...
>   creationTimestamp: 2017-06-27T16:35:34Z
> ...

Query for specific data directly from a db file:

auger extract -f <boltdb-file> --template="{{.Value.kind}} {{.Value.metadata.name}}" --filter=".Value.metadata.namespace=default"
> Endpoints kubernetes
> Service kubernetes
> ...

Consistency and corruption checking

First get a checksum and latest revsion from one of the members:

auger checksum -f <member-1-boltdb-file>
> checksum: 1282050701
> revision: 7

Then compare it with the other members:

auger checksum -f <member-2-boltdb-file> -r 7
> checksum: 1282050701
> revision: 7

auger checksum -f <member-3-boltdb-file> -r 7
> checksum: 8482350767
> revision: 7
# Oh noes! The checksum should have been the same!

TODO

Warn if attempting to read data written by a different version of kubernetes
Add detection of unrecognized fields in stored data, which would suggest data was written with newer version of proto schema
Build and publish releases for all recent kubernetes versions (1.6+)

divanodestiny/auger