service-config

Service Configuration Demo

This demo illustrates some of the available service configuration options

Deploy

kubectl apply -f service.yaml

After deployment, the config application will expose the following endpoints:

• / Landing page with links to this endpoints
• /kn Knative-specific data as defined in the Runtime Contract
• /req Request context with environment variables and headers
• /res Serving node info (Hostname, OS, Boot-time) and Pod available Memory/CPU resources
• /log Content of specific log or log list in dir (e.g. /log?logpath=/var/log/app.log)

Demo

https://config.demo.knative.tech/

Endpoint How-to

The JSON outputting endpoints (/kn, /req, /res) include request metadata object. This provides context for each response and is useful when persisting returned data for evaluation/texting.

{
    "meta": {
        "id": "215bb44e-0513-44a5-a640-fc1546daf294",
        "ts": "2019-01-04T20:09:12.52097224Z",
        "uri": "/req",
        "host": "config.demo.knative.tech",
        "method": "GET"
    },
    ...

req - HTTP Request

The /req endpoint provides an easy way to eval expected environment variables or headers for your requests. For example to get a release version of the config app you would execute:

curl -s https://config.demo.knative.tech/req |  jq '.envs.RELEASE'

Or to get your user-agent as seen by the Knative service

curl -s https://config.demo.knative.tech/req |  jq '.head."user-agent"'

/node (Serving Node)

The /node endpoint provides information about the node which is serving your request. For example to see the boot time of that node and its hostname

curl -s https://config.demo.knative.tech/res |  jq '.node.bootTs,.meta.host'

/kn (Knative)

The /kn endpoint is what you would use to evaluate Knative-specific data. In addition to the Knative environment variables (PORT and ones prefixed by K_ like K_CONFIGURATION, K_REVISION, and K_SERVICE), the /kn endpoint also exposes information about the recommended file system mounts (e.g. /tmp, /var/log, or /dev/log).

To test for example if the /etc/hosts has the required R/W permissions you can run this query. It searches for comment in the returned document where access group name == "DNS" and and the item within that group has the path == /etc/hosts

curl -s https://config.demo.knative.tech/kn \
  | jq -r --arg group "DNS" \
    '.access[] | if .group == $group then . else empty end' \
    | jq -r --arg path "/etc/hosts" \
      '.list[] | if .path == $path then .comment else empty end'

/log

The /log endpoint returns the log file specified by the logpath parameter in query string. ((e.g. /log?logpath=/var/log/config.log)). If the logpath parameter is a directly the /log will return a list of content in that directory.

Note, config by default writes logs to stdout unless the LOG_TO_FILE environment variable is set (anything other than "" will do). If that variable is set, ktest will output its own logs to /var/log/config.log

Note, currently the /log endpoint will not return any logs larger than 1MB.

To search log you can pipe the /log output through greb. For example to find out the port on which the server started

curl -s https://config.demo.knative.tech/log?logpath=/var/log/config.log \
  | grep 'Server starting on port'