Hot Reload

Last updated 4 months ago

Hot Reload

When the local-kubernetes provider is used, container modules can be configured to hot-reload their running services when the module's sources change (i.e. without redeploying). In essence, hot-reloading copies source files into the appropriate running containers when code is changed by the user.

For example, services that can be run with a file system watcher that automatically update the running application process when sources change (e.g. nodemon, Django, Ruby on Rails, and many other web app frameworks) are a natural fit for this feature.

Usage

Currently, modules configured for hot reloading are only deployed with hot reloading enabled when they're deployed via garden deploy -w or garden dev; and not, for example, when deployed via garden deploy without the -w flag.

Subsequently deploying a service belonging to a module configured for hot reloading via garden deploy (without the watch flag) results in the service being redeployed in standard configuration. (See this link for a more technical discussion.)

Since hot reloading is triggered via Garden's file system watcher, hot reloading only occurs while a garden deploy -w, garden build -w, or garden dev command is running.

Quick example

Following is a simple example of a module configured for hot reloading:

module:
description: My Test Service
name: test-service
type: container
hotReload:
sync:
- target: /app/
services:
- name: test-service
args: [npm, start] # runs `node main.js`
hotReloadArgs: [npm, run, dev] # runs `nodemon main.js`

In the above, the hotReload field specifies the destination path inside the running container that the module's (top-level) directory (where its garden.yml resides) is synced to.

Note that only files tracked in version control are synced, e.g. respecting .gitignore.

If a source is specified along with target, that subpath in the module's directory is synced to the target instead of the default of syncing the module's top-level directory.

You can configure several such source/target pairs, but note that the source paths must be disjoint, i.e. a source path may not be a subdirectory of another source path within the same module. Here's an example:

sync:
- source: /foo
target: /app/foo
- source: /bar
target: /app/bar

Lastly, hotReloadArgs specifies the arguments to use to run the container (when deployed with hot reloading enabled). If no hotReloadArgs are specified, args is also used in hot reload mode.