About conn-check¶

conn-check allows for checking connectivity with external services.

You can write a config file that defines services that you need to have access to, and conn-check will check connectivity with each.

It supports various types of services, all of which allow for basic network checks, but some allow for confirming credentials work also.

Configuration¶

The configuration is done via a yaml file. The file defines a list of checks to do:

- type: tcp
  host: localhost
  port: 80
- type: tls
  host: localhost
  port: 443
  disable_tls_verification: false

Each check defines a type, and then options as appropriate for that type.

For a step by step guide on configuring conn-check for your application see the tutorial.

Check Types¶

tcp¶

A simple tcp connectivity check.

host: The host.
port: The port.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

tls¶

A check that uses TLS (ssl is a deprecated alias for this type).

host: The host.
port: The port.
disable_tls_verification: Optional flag to disable verification of TLS certs and handshake. Default: false.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

udp¶

Check that sending a specific UDP packet gets a specific response.

host: The host.
port: The port.
send: The string to send.
expect: The string to expect in the response.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

http¶

Check that a HTTP/HTTPS request succeeds (https also works).

url: The URL to fetch.
method: Optional HTTP method to use. Default: “GET”.
expected_code: Optional status code that defines success. Default: 200.
proxy_url: Optional HTTP/HTTPS proxy URL to connect via, including protocol, if set proxy_{host,port} are ignored.
proxy_host: Optional HTTP/HTTPS proxy to connect via.
proxy_port: Optional port to use with proxy_host. Default: 8000.
headers:: Optional headers to send, as a dict of key-values. Multiple values can be given as a list/tuple of lists/tuples, e.g.: [('foo', 'bar'), ('foo', 'baz')]
body:: Optional raw request body string to send.
disable_tls_verification:: Optional flag to disable verification of TLS certs and handshake. Default: false.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).
allow_redirects: Optional flag to Follow 30x redirects. Default: false.
params: Optional dict of params to URL encode and pass in the querystring.
cookies: Optional dict of cookies to pass in the request headers.
auth: Optional basic HTTP auth credentials, as a tuple/list: (username, password).
digest_auth: Optional digest HTTP auth credentials, as a tuple/list: (username, password).

amqp¶

Check that an AMQP server can be authenticated against.

host: The host.
port: The port.
username: The username to authenticate with.
password: The password to authenticate with.
use_tls: Optional flag whether to connect with TLS. Default: true.
vhost: Optional vhost name to connect to. Default ‘/’.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

postgres¶

Check that a PostgreSQL db can be authenticated against (postgresql also works).

host: The host.
port: The port.
username: The username to authenticate with.
password: The password to authenticate with.
database: The database to connect to.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

redis¶

Check that a redis server is present, optionally checking authentication.

host: The host.
port: The port.
password: Optional password to authenticatie with.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

memcache¶

Check that a memcached server is present (memcached also works).

host: The host.
port: The port.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

mongodb¶

Check that a MongoDB server is present (mongo also works).

host: The host.
port: Optional port. Default: 27017.
username: Optional username to authenticate with.
password: Optional password to authenticate with.
database: Optional database name to connect to, if not set the test database will be used, if this database does not exist (or is not available to the user) you will need to provide a database name.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

smtp¶

Check that we can reach, authenticate with and send an email using an SMTP server.

Note 1: if this check succeeds an email is actually sent to the email defined in to_address, be careful how this is check is configured so it doesn’t unintentionally spam anyone.

Note 2: only EHLO/HELO over a TLS connection is supported with the use_tls flag, this check cannot currently create new TLS connection using the STARTTLS Extension.

host: The host.
port: The port, normally 465 for TLS and 25 for plaintext.
username: Username to authenticate with.
password: Password to authenticate with.
from_address:: Email address to send from.
to_address:: Email address to send to.
message:: Optional email body.
subject:: Optional email subject.
helo_fallback:: Optional flag that defines whether to fall back to HELO if the EHLO extended command set fails.
use_tls:: Optional flag to enable TLS security on connection. Default: true.
timeout: Optional connection timeout in seconds. Default: 10 (or value from --connect-timeout).

Tags¶

Every check type also supports a tags field, which is a list of tags that can be used with the --include-tags and --exclude-tags arguments to conn-check.

Example YAML:

- type: http
  url: http://google.com/
  tags:
    - external

To run just “external” checks:

conn-check --include-tags=external ...

To run all the checks except external:

conn-check --exclude-tags=external

Buffered/Ordered output¶

conn-check normally executes with output to STDOUT buffered so that the output can be ordered, with failed checks being printed first, grouping by destination etc.

If you’d rather see results as they available you can use the -U/--unbuffered-output option to disable buffering.

Generating firewall rules¶

conn-check includes the conn-check-export-fw utility which takes the same arguments as conn-check but runs using --dry-run mode and outputs a set of egress firewall rules in an easy to parse YAML format, for example:

# Generated from the conn-check demo.yaml file
egress:
- from_host: mydevmachine
  ports: [8080]
  protocol: udp
  to_host: localhost
- from_host: mydevmachine
  ports: [80, 443]
  protocol: tcp
  to_host: login.ubuntu.com
- from_host: mydevmachine
  ports: [6379, 11211]
  protocol: tcp
  to_host: 127.0.0.1

You can then use this output to generate your environments firewall rules (e.g. with EC2 security groups, OpenStack Neutron, iptables etc.).

conn-check-convert-fw is a utility that does just this, it accepts multiple firewall rule YAML files, merges/de-dupes them, and outputs commands for AWS, Openstack Neutron, OpenStack Nova (client), iptables, and ufw (mostly for testing purposes).

It is designed for this workflow:

On each host you run conn-check from, you run conn-check-export-fw to generate a YAML file containing egress firewall rules.

Each of these files is transfered to a host with the correct DNS entries for the egress hosts.

On this host conn-check-convert-fw is run to generate a set of commands for your firewall.

These commands are audited by a human / possibly merged with other rules, such as adding ingress rules, and then run to update your environment’s firewall.

Building wheels¶

To allow for easier/more portable distribution of this tool you can build conn-check and all its dependencies as Python wheels:

make clean-wheels
make build-wheels
make build-wheels-extra EXTRA=amqp
make build-wheels-extra EXTRA=redis

The build-wheels make target will build conn-check and its base dependencies, but to include the optional extra dependencies for other checks such as amqp, redis or postgres you need to use the build-wheels-extra target with the EXTRA env value.

By default all the wheels will be placed in ./wheels.

Automatically generating conn-check YAML configurations¶

The conn-check-configs package contains utilities/libraries for generating checks from existing application configurations and environments, e.g. from Django settings modules and Juju environments.