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Transparent Proxying
In order to automatically intercept traffic from and to a service through a kuma-dp
data plane proxy instance, Kuma utilizes a transparent proxying using iptables
.
Transparent proxying helps with a smoother rollout of a Service Mesh to a current deployment by preserving existing service naming and as the result - avoid changes to the application code.
Kubernetes
On Kubernetes kuma-dp
leverages transparent proxying automatically via iptables
installed with kuma-init
container or CNI.
All incoming and outgoing traffic is automatically intercepted by kuma-dp
without having to change the application code.
Kuma integrates with a service naming provided by Kubernetes DNS as well as providing its own Kuma DNS for multizone service naming.
Universal
On Universal kuma-dp
leverages the data plane proxy specification associated to it for receiving incoming requests on a pre-defined port.
There are several advantages for using transparent proxying in universal mode:
- Simpler Dataplane resource, as the
outbound
section becomes obsolete and can be skipped. - Universal service naming with
.mesh
DNS domain instead of explicit outbound likehttps://localhost:10001
. - Support for hostnames of your choice using VirtualOutbounds that lets you preserve existing service naming.
- Better service manageability (security, tracing).
Setting up the service host
Prerequisites:
kuma-dp
,envoy
, andcoredns
must run on the worker node – that is, the node that runs your service mesh workload.coredns
must be in the PATH so thatkuma-dp
can access it.- You can also set the location with the
--dns-coredns-path
flag tokuma-dp
.
- You can also set the location with the
Kuma comes with kumactl
executable which can help us to prepare the host. Due to the wide variety of Linux setup options, these steps may vary and may need to be adjusted for the specifics of the particular deployment.
The host that will run the kuma-dp
process in transparent proxying mode needs to be prepared with the following steps executed as root
:
-
Create a new dedicated user on the machine.
useradd -u 5678 -U kuma-dp
-
Redirect all the relevant inbound, outbound and DNS traffic to the Kuma data plane proxy.
kumactl install transparent-proxy \ --kuma-dp-user kuma-dp \ --skip-resolv-conf \ --redirect-dns
Please note that this command will change the host iptables
rules.
The changes will persist over restarts, so this command is needed only once. Reverting to the original state of the host can be done by issuing kumactl uninstall transparent-proxy
.
Data plane proxy resource
In transparent proxying mode, the Dataplane
resource should omit the networking.outbound
section and use networking.transparentProxying
section instead.
type: Dataplane
mesh: default
name:
networking:
address:
inbound:
- port:
tags:
kuma.io/service: demo-client
transparentProxying:
redirectPortInbound: 15006
redirectPortOutbound: 15001
The ports illustrated above are the default ones that kumactl install transparent-proxy
will set. These can be changed using the relevant flags to that command.
Invoking the Kuma data plane
It is important that the kuma-dp
process runs with the same system user that was passed to kumactl install transparent-proxy --kuma-dp-user
.
When systemd is used, this can be done with an entry User=kuma-dp
in the [Service]
section of the service file.
When starting kuma-dp
with a script or some other automation instead, we can use runuser
with the aforementioned yaml resource as follows:
runuser -u kuma-dp -- \
/usr/bin/kuma-dp run \
--cp-address=https://<IP or hostname of CP>:5678 \
--dataplane-token-file=/kuma/token-demo \
--dataplane-file=/kuma/dpyaml-demo \
--dataplane-var name=dp-demo \
--dataplane-var address=<IP of VM> \
--dataplane-var port=<Port of the service> \
--binary-path /usr/local/bin/envoy
You can now reach the service on the same IP and port as before installing transparent proxy, but now the traffic goes through Envoy. At the same time, you can now connect to services using Kuma DNS.
firewalld support
If you run firewalld
to manage firewalls and wrap iptables, add the --store-firewalld
flag to kumactl install transparent-proxy
. This persists the relevant rules across host restarts. The changes are stored in /etc/firewalld/direct.xml
. There is no uninstall command for this feature.
Upgrades
Before upgrading to the next version of Kuma, make sure to run kumactl uninstall transparent-proxy
and only then replace the kumactl
binary.
This will ensure smooth upgrade and no leftovers from the previous installations.
Configuration
Intercepted traffic
By default, all the traffic is intercepted by Envoy. You can exclude which ports are intercepted by Envoy with the following annotations placed on the Pod
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-app
namespace: kuma-example
spec:
...
template:
metadata:
...
annotations:
# all incomming connections on ports 1234 won't be intercepted by Envoy
traffic.kuma.io/exclude-inbound-ports: "1234"
# all outgoing connections on ports 5678, 8900 won't be intercepted by Envoy
traffic.kuma.io/exclude-outbound-ports: "5678,8900"
spec:
containers:
...
You can also control this value on whole Kuma deployment with the following Kuma CP configuration
KUMA_RUNTIME_KUBERNETES_SIDECAR_TRAFFIC_EXCLUDE_INBOUND_PORTS=1234
KUMA_RUNTIME_KUBERNETES_SIDECAR_TRAFFIC_EXCLUDE_OUTBOUND_PORTS=5678,8900
Reachable Services
By default, every data plane proxy in the mesh follows every other data plane proxy. This may lead to performance problems in larger deployments of the mesh. It is highly recommended to define a list of services that your service connects to.
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-app
namespace: kuma-example
spec:
...
template:
metadata:
...
annotations:
# a comma separated list of kuma.io/service values
kuma.io/transparent-proxying-reachable-services: "redis_kuma-demo_svc_6379,elastic_kuma-demo_svc_9200"
spec:
containers:
...
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