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Tricot is a reverse-proxy for exposing your services via TLS that integrates well with Consul and Nomad.
Tricot does the following things:
- Find the services running on your cluster that expose an HTTP or HTTPS access point, by listing the Consul catalog
- Request TLS certificats via Let's Encrypt for the domain names you are exposing
- Store these certificates in Consul's key-value store
- Renew these certificates when they reach half of their designated lifetime
- Expose an HTTPS port where all of the requests are forwarded to one of the back-end services, based on matching rules (see below)
- Expose an HTTP port that redirects everything to the HTTPS port (the HTTP port is mandatory as it is also used for Let's Encrypt validation)
- Load-balance incoming requests among different available backends, or redirect all requests to the best-available matching backend, depending on desired configuration
- Optionnally, compress data comming from the backend before forwarding it to the client
Tricot uses the following environment variables for its configuration (they can also be passed as command line arguments, see
TRICOT_LETSENCRYPT_EMAIL(mandatory): the e-mail address used to register a Let's encrypt account
TRICOT_NODE_NAME(mandatory): the name in Consul of the node on which this instance of Tricot is running
http://127.0.0.1:8500): the HTTP or HTTPS address at which the Consul catalog can be reached
TRICOT_CONSUL_CLIENT_KEY(optional): parameters necessary to access Consul over HTTPS when cluster TLS is enabled
tricot/): the prefix in Consul's key-value store under which Tricot stores its data (the certificates it obtained from Lets Encrypt)
0.0.0.0:80): the HTTP address and port on which Tricot listens
0.0.0.0:443): the HTTPS address and port on which Tricot listens
false): whether to enable transparent compression of data coming back from backends
Here is an example of how to run Tricot as a Nomad service (in this example it also integrates with Diplonat).
Adding and priorizing backends
Backends are configured by adding tags of the following form to the services in Consul:
tricot myapp.example.com: indicates that Tricot should get a TLS certificate for domain myapp.example.com and route traffic for this domain to this service
tricot myapp.example.com 10: same but with a priority of 10. This is lower than the default priority value of 100, so Tricot will only use this rule if no higher-priority services are available.
tricot myapp.example.com/path/to_subresource: same but indicates that only requests whose paths start with
/path/to/subresourceshould be routed to this service
tricot myapp.example.com/path/to_subresource 10: combining the previous two examples
tricot-https myapp.example.com: same, but indicates that the backend service handling the request expects an HTTPS request and not an HTTP request. In this case, Tricot will do everything in its power to NOT verify the backend's TLS certificate (ignore self-signed certificate, ignore TLS hostname, etc).
tricot-add-header Access-Control-Allow-Origin *: add the
Access-Control-Allow-Origin: *header to all of the HTTP responses when they are proxied back to the client
tricot-global-lb: load-balance incoming requests to all matching backends
tricot-site-lb: load-balance incoming requests to all matching backends that are in the same site (geographical location); when site information about nodes is not available, this is equivalent to
Any number of such rules can be combined freely.
How Tricot matches backends
Tricot priorizes backend nodes in the following order:
- Select rule with the highest explicitly set priority value
- Select rule with the longest path prefix that matches the incoming request
- Select rule that redirects request to the same node Tricot is running on, except
- Select rule that redirects request to a node that is running in the same site (geographical region, datacenter, whatever) than the node Tricot is running on, based on the metadata key
sitein Consul's node information, if such information is available, except if
- Round-robin selection of backend nodes
Knowing what Tricot is doing
Logs are the privileged place to get information about what Tricot is doing. You can set the log level by changing the
RUST_LOG environment variable. The following log levels are avaialble:
RUST_LOG=tricot=warn: Tricot will only show warning and errors, it should be quite quiet
RUST_LOG=tricot=info: Tricot will dump the proxy configuration (the set of rules it uses to match backends) each time it changes, and will show a line for each incoming request (but it won't indicate which backend the request was routed to). You will also get information about certificate obtention and renewal using Let's Encrypt.
RUST_LOG=tricot=debug: Tricot will show for each request the backend to which it is routed. It will also show all of its interactions with Consul
RUST_LOG=tricot=trace: Tricot will show details such as the request's headers for all request at all stages of proxying.