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Add recommendation around service name impacting the pods

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This length of the service name impacts the number of pods that can run
in a namespace with maximum number of services tested deployed - 5000.
This commit adds a recommendation for the user to be able to plan their
applications accordingly.
This commit is contained in:
Naga Ravi Chaitanya Elluri
2020-12-09 02:40:02 -05:00
parent dbf1cafcba
commit 593b5ca848
1 changed files with 17 additions and 0 deletions
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17
modules/how-to-plan-your-environment-according-to-application-requirements.adoc
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@@ -167,3 +167,20 @@ links in the deployment's service specification file to overcome this:
labels:
template: deploymentConfigTemplate
----
The number of application pods that can run in a namespace is dependent on the number of services and the
length of the service name when the environment variables are used for service discovery. `ARG_MAX` on the system
defines the maximum argument length for a new process and it is set to `2097152 KiB` by default. The Kubelet injects
environment variables in to each pod scheduled to run in the namespace including:
* `<SERVICE_NAME>_SERVICE_HOST=<IP>`
* `<SERVICE_NAME>_SERVICE_PORT=<PORT>`
* `<SERVICE_NAME>_PORT=tcp://<IP>:<PORT>`
* `<SERVICE_NAME>_PORT_<PORT>_TCP=tcp://<IP>:<PORT>`
* `<SERVICE_NAME>_PORT_<PORT>_TCP_PROTO=tcp`
* `<SERVICE_NAME>_PORT_<PORT>_TCP_PORT=<PORT>`
* `<SERVICE_NAME>_PORT_<PORT>_TCP_ADDR=<ADDR>`
The pods in the namespace will start to fail if the argument length exceeds the allowed value and the number of
characters in a service name impacts it. For example, in a namespace with 5000 services, the limit on the service name
is 33 characters, which enables you to run 5000 pods in the namespace.