Plain-language glossary#

You do not need to memorize these terms. Look them up when a setting or message uses one.

Applications and servers#

Term	What it means in Zela
Cluster	Your group of servers, managed together
Manager / control plane	The computer and Zela program that provide the dashboard and coordinate work
Worker / host / node	A Linux server where applications run
Agent	The small `zela-worker` program that lets the manager communicate with Docker and collect host measurements
Docker	Software on a worker that runs packaged applications in containers
Container image	The packaged application used to create a container. `nginx:alpine` is an example
Image tag	The version label after `:` in an image name. Changing it can change the software you deploy
Container	One instance created from an image, with its own running process and local writable files
Deployment	The saved application settings Zela manages: image, copies, resources, and placement
Replica	One copy of a deployment. Two replicas mean two containers
Stateless application	An app whose important data is stored elsewhere, so its containers can be replaced without losing that data
Volume / persistent storage	Storage intended to keep data when a container is replaced. Zela does not copy it between workers
Environment variable	A named application setting, such as `APP_ENV=production`; it may contain a secret
CPU / memory / RAM	Processing power and working memory available to an application
Reservation	Resources Zela accounts for when deciding whether a worker has room. It is different from measured usage

Status and actions#

Term	Meaning
Online	The manager can reach the worker. Check freshness and any reported errors too
Active	A worker may receive new application placements
Paused	No new placements; existing containers continue running
Drain	Try to move eligible managed applications away before server maintenance. Check the result before rebooting
Scale	Change the number of application copies
Rollout / update image	Replace application copies using another image
Degraded	The deployment is not meeting its intended running state; inspect its error and replicas
Operation	A tracked change, such as deploying or draining. Starting it is not the same as completing it
Failover / recovery	Recreate lost managed application copies on another suitable worker when possible
High availability / HA	Extra managers waiting to take over management if the active manager fails; this does not replicate your application data
Acknowledge	Mark an alert as reviewed. It does not fix the underlying problem

Networking and access#

Term	Meaning
IP address / hostname	An address identifying a computer, such as `10.0.0.21` or `worker.example.com`
Port	A numbered entry point on a computer. One computer can serve different programs on different ports
Published port	A mapping from a worker's port to an application's container port. `8081:80` means worker port 8081 leads to container port 80
localhost / 127.0.0.1	The computer where the command or browser is running; inside a container it refers to that container
Cluster mesh / WireGuard	The optional encrypted private network connecting Linux workers
Subnet / CIDR	An address range. `10.200.0.0/16` describes the size and location of one range; ask your network administrator to choose a non-overlapping range
Peer endpoint	The worker hostname or IP address the other workers use for their encrypted network connection
Bridge network	A Docker network local to one worker. Creating one does not connect different workers
VIP / virtual IP	A stable private service address that can send traffic to the deployment's healthy copies
DNS	The system that turns a name into an address. Internal names such as `web.zela` are different from public website DNS
Edge proxy / route	A worker service and rule that forward a website hostname/path to an application
HTTPS / TLS certificate	Encrypted browser communication and the certificate that identifies the server
SSH	A secure way to access a server. Zela can use it to install and manage a worker
SSH login key	Your private key used to sign in to a server; store it in the Secrets vault
SSH host public key	The server's identity. Verify it through a trusted source before giving it to Zela
Administrator token	The secret used to sign in and fully control the cluster
Vault key	The master encryption key used to unlock saved SSH secrets. Keep it with your recovery materials
MCP	The connection that lets an AI assistant call Zela's supported tools
Read / management access	Permission to inspect information / permission to make changes as well
PostgreSQL	The database used to save Zela's configuration and history; separate from application databases