cat'a-dog

Quick start

Using Docker

Run the following command to start a new Docker container with catadog.

docker run --rm -d --name catadog ghcr.io/datadog/catadog

Global command

Run the following commands to install and run catadog locally.

gem install catadog
catadog

Per project via a Gemfile

cat > Gemfile <<'EOF'
source 'https://rubygems.org'

gem 'catadog'
EOF
bundle install
catadog

For `catadog` development

Run the following commands to install and run catadog locally.

git clone https://github.com/DataDog/catadog
cd catadog
bundle install
bundle exec catadog

Now start your agent and app!

Remember to do one of the following:

configure your app's agent connection to hit on the correct port
configure your agent to listen to another port, have catadog listen on 8126 as the default, and point to the new agent's port by using the settings below

Examples

Note that if using Docker, replace bundle exec catadog with docker run ghcr.io/datadog/catadog in the examples below.

Change listening host and port (defaults to 127.0.0.1:8128)

bundle exec catadog -h 0.0.0.0 -p 8888

Change agent host and port to proxy to (defaults to 127.0.0.1:8126)

bundle exec catadog --agent-host 10.1.2.3 --agent-port 8127

Silence WEBrick logs (they're on stderr):

bundle exec catadog 2>/dev/null

Record stuff (they're on stdout):

bundle exec catadog > dump.json

Record stuff, one file per request:

bundle exec catadog --record

Use the sink mock, and don't forward to a real agent (mock route misses fall back to 404):

bundle exec catadog --mock :Sink --no-forward

Bring your own mock! (you can use --mock multuiple times)

bundle exec catadog --mock /path/to/mock.rb:MockMiddlewareClass --no-forward

Run program as a background process

bundle exec catadog --daemon

Select specific areas:

bundle exec catadog | jq 'select(.kind=="info")'
bundle exec catadog | jq 'select(.kind=="traces")
bundle exec catadog | jq 'select(.kind=="telemetry")'
bundle exec catadog | jq 'select(.kind=="rc")'

Show only request body of traces that have a span name rack.request:

bundle exec catadog | jq 'select(.kind=="traces") | .request.body | .[] | select(.[].name == "rack.request")'

Ask telemetry if appsec is enabled:

bundle exec catadog | jq 'select(.kind=="telemetry") | .request.body | .payload.additional_payload | .[] | select(.name == "appsec.enabled")'

Ask telemetry the list of reported dependencies and their versions, formatted as tab separated:

bundle exec catadog | jq 'select(.kind=="telemetry") | .request.body | .payload.dependencies | .[] | [.name, .version] | @tsv' -r

Ask telemetry which integrations are enabled:

bundle exec catadog | jq 'select(.kind=="telemetry") | .request.body | .payload.integrations | .[] | select(.enabled)'

Show RC client config state as it evolves:

bundle exec catadog | jq 'select(.kind=="rc") | .request.body.client.state.config_states'

Show RC client cached targets as they evolve:

bundle exec catadog | jq 'select(.kind=="rc") | .request.body.cached_target_files'

Show RC targets as they are received:

bundle exec catadog | jq 'select(.kind=="rc") | .response.body.target_files'

Show RC targets in both request and response as they evolve:

bundle exec catadog | jq 'select(.kind=="rc") | { cached: .request.body.cached_target_files | map(.path), received: .response.body.targets.signed.targets }'

Show the contents of the ASM_DD product traget as it is received

bundle exec catadog | jq 'select(.kind=="rc") | .response.body.target_files | .[] | select(.path | test("ASM_DD"))'

Show the contents of the crs-913-110 rule as it is received:

bundle exec catadog | jq 'select(.kind=="rc") | .response.body.target_files | .[] | select(.path | test("ASM_DD")) | .parsed.rules | .[] | select(.id == "crs-913-110")'

Show the contents of the blocked ips list:

bundle exec catadog | jq 'select(.kind=="rc") | .response.body.target_files | .[] | select(.path | test("ASM_DATA/blocked_ips"))'

Using Docker Compose

By leveraging the docker-compose.yaml file, you can automatically connect your app to catadog and your datadog agent.

First, instrument your app with the datadog gem.

Then, include the following environment variables in a .env file.

DD_ENV=env-name.dev
DD_HOSTNAME=host-name
DD_API_KEY=<api_key>

Update your docker-compose.yaml such as below.

services:
  app:
    ...
  catadog:
    image: ghcr.io/datadog/catadog:latest
    command: --agent-host agent
    depends_on:
      - agent
    ports:
      - "8126:8128"
  agent:
    image: datadog/agent
    env_file:
      - ".env"
    environment: 
      - DD_APM_ENABLED=true
      - DD_BIND_HOST=0.0.0.0
      - DD_APM_NON_LOCAL_TRAFFIC=true
      - DD_REMOTE_CONFIGURATION_ENABLED=true

Run the following commands.

docker compose build
docker compose up -d

Finally, see your app send traces to catadog!

The big idea

dd-trace-cat

at DataDog/dd-trace-cat
node project
sink for /v0.4/traces only
dumb '200 OK' as response

catadog

support everything else
decode known encoded content
use Unix as IDE
answer properly

TODO:

cli: better interface (command args)
traces: output .dot format (graphviz + sixel)
traces: GUI like dd-trace-cat
all: mock (static, dynamic)
all: record, replay

catadog

Runtime