Port Forwarding

How to use mirrord for port forwarding

Regular port-forwarding

The port-forward command allows you to forward traffic from a local port to any destination that the mirrord targeted pod has access to, in a similar way to kubectl port-forward. The traffic is forwarded as-if it was coming from the target pod, meaning it has access to destinations that might be outside the cluster, like third-party APIs, depending on what's accessible by the target pod.

To use port-forwarding with MySQL databases, at least version 3.177.0 of mirrord is required.

You can use the command like so:

mirrord port-forward --target <target-path> -L <local port>:<remote address>:<remote port>

For example, to forward traffic from localhost:8080 to an in-cluster service py-serv listening on port 80:

mirrord port-forward -L 8080:py-serv:80

Reverse port-forwarding

It also allows for reverse port forwarding, where traffic is redirected from a port on the target pod or workload to a local port, like so:

mirrord port-forward --target <target-path> -R <remote port>:<local port>

For example, to forward traffic from an in-cluster deployment py-serv listening on port 80 to localhost:8080:

mirrord port-forward --target deployment/py-serv -R 80:8080

In addition, multiple ports can be forwarded in one direction or both directions simultaneously in the same command by providing each source and destination as a separate -L or -R argument.

Regular port forwarding with an -L can be done in targetless mode and does not require specifying any target. Reverse port forwarding always requires a target.

More details

• The local port component of the -L argument is optional, and without it the same port will be used locally as on the remote.

• The same is true of the -R argument: if one port number is provided, it will be used for both local and remote ports.

• Port-forwarding only supports TCP, not UDP.

• The remote address can be an IPv4 address or a hostname - hostnames are resolved in the cluster.

• In regular port forwarding (-L) connections are made lazily and hostname resolution is attempted only data is sent to the local port.

• Reverse forwarding (-R) can read the feature.network.incoming section of a mirrord config file when the file is passed to the command with -f.