Task Pipeline Configuration
Nx runs tasks in the most efficient way possible. The nx.json file is the place where you can configure how Nx does it.
Run Tasks in Parallel
If you want to increase the number of processes running tasks to, say, 5 (by default, it is 3), pass the following:
npx nx build myapp --parallel=5
Note, you can also change the default in nx.json, like this:
{
"tasksRunnerOptions": {
"default": {
"runner": "nx/tasks-runners/default",
"options": {
"cacheableOperations": [],
"parallel": 5
}
}
}
}
Define Task Dependencies (aka Task Pipelines)
To ensure tasks run in the correct order, Nx needs to know how the tasks depend on each other. Add the following to nx.json:
{
...
"targetDefaults": {
"build": {
"dependsOn": ["^build"]
}
}
}
With this, Nx knows that before it can build a project, it needs to build all of its dependencies first. There are, however, no constraints on tests.
This mechanism is very flexible. Let's look at this example:
{
...
"targetDefaults": {
"build": {
"dependsOn": ["^build", "prebuild"]
},
"test": {
"dependsOn": ["build"]
}
}
}
Note, older versions of Nx used targetDependencies instead of targetDefaults. Both still work, but targetDefaults is recommended.
When running nx test myproj, the above configuration would tell Nx to
- Run the
testcommand formyproj - But since there's a dependency defined from
test -> build(seetest:["build"]), Nx runsbuildformyprojfirst. builditself defines a dependency onprebuild(on the same project) as well asbuildof all the dependencies. Therefore, it will run theprebuildscript and will run thebuildscript for all the dependencies.
Note, Nx doesn't have to run all builds before it starts running tests. The task orchestrator will run as many tasks in parallel as possible as long as the constraints are met.
Situations like this are pretty common:
Because we described the rules in nx.json, they will apply to all the projects in the repo. You can also define project-specific rules by adding them to the project's configuration.
{
...
"nx": {
"targets": {
"test": {
"dependsOn": [
"build"
]
}
}
}
}