To meet the origin verification required by the Nomad API, NGINX will have to override the existing Origin header to match the host address. The fulfill the handshake NGINX will need to forward the Connection and Upgrade headers. You can experience this in the Web UI by going to clicking the Exec button, choosing the task, and attempting to run the command /bin/sh. This results in exec sessions immediately terminating. Nomad does this verification by checking if the Origin header of the handshake request is equal to the address of the Nomad API.īy default NGINX will not fulfill the handshake or the origin verification. The server-side of a WebSocket connection needs to verify trusted origins on its own. WebSockets also do not support CORS headers. The handshake is an HTTP request with special Connection and Upgrade headers. The way a WebSocket connection is established is through a handshake request. This is used to receive changes to the remote output as well as send commands and signals from the browser-based terminal. WebSockets are necessary for the exec API because they allow bidirectional data transfer. This is achieved using the exec API which is implemented using WebSockets. Enable WebSocket connectionsĪs of Nomad 0.11.0, the Web UI has supported interactive exec sessions with any running task in the cluster. Restart the NGINX docker container to load these configuration changes. There will also be this additional error in the browser developer tools console. Logs will not load and eventually the following error will appear in the UI. To observe this issue, visit the task logs page of your sample job by first visiting the sample job at then clicking into the most recent allocation, then clicking into the fs-example task, then clicking the logs tab. Older browsers may not support this technology, in which case logs are streamed using a simple polling mechanism. Proxy buffering causes logs events to not stream because they will be temporarily captured within NGINX's proxy buffer until either the connection is closed or the proxy buffer size is hit and the data is finally flushed to the client. NGINX by default will buffer proxy responses in an attempt to free up connections to the backend server being proxied as soon as possible. When possible the Web UI will use a streaming HTTP request to stream logs on the task logs page. To observe the proxy time out a connection, visit the Nomad jobs list through the proxy at with your Browser's developer tools open. NGINX has a default proxy timeout of 60 seconds while Nomad's blocking query system will leave connections open for five minutes by default. A consequence of this design is that HTTP requests aren't always expected to be short-lived. It is also faster since a connection will close as soon as new information is available rather than having to wait for the next iteration of a polling loop. This is advantageous over traditional polling which results in more requests that often return no new information. Blocking queries are an implementation of long-polling which works by keeping HTTP connections open until server-side state has changed. This is achieved using the blocking queries to the Nomad API. The Nomad Web UI will live-reload all data to make sure views are always fresh as Nomad's server state changes. If the proxy closes the connection early because of a connection timeout, it could prevent the Web UI from continuing to live-reload data. The Nomad Web UI uses long-lived connections for its live-update feature. At that point you can visit to visit the Nomad Web UI through the NGINX reverse proxy. NGINX will be started as soon as Docker has finished pulling layers. That for the purposes of this tutorial by advertising an incorrect http address.Ĭreate a file named nomad.hcl with the following configuration snippet. UI users to not have direct access to the Nomad client nodes. Here is what you will need for this guide:īecause of best practices around least access to nodes, it is typical for Nomad This tutorial assumes basic familiarity with Nomad and NGINX. As you learn about each issue, you will deploy NGINX configuration changes that will address it. Issues common to default proxy configurations will be discussed and demonstrated. This tutorial will explore common configuration changes necessary when reverse proxying Nomad's Web UI. To ensure every feature in the Nomad UI remains fully functional, you must properly configure your reverse proxy to meet Nomad's specific networking requirements. A reverse proxy has the added benefits of enabling multiple web services to share a single, memorable domain and authentication to view internal systems. NGINX can be used to reverse proxy web services and balance load across multiple instances of the same service.
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