Concepts > Parallel Scripts#

Parallel Max Value#

When running scripts in parallel, you have control over how many concurrent scripts can run at the same time.

You can pass a number value, a percentage value (e.g. 50%), or one of the keywords "auto", "default", or "unbounded" to the parallel max option.

Value Types#

• A plain number sets the limit to the exact number of concurrent scripts. Setting the max to 2 then only allows two scripts to run at the same time.

• A value of "auto" sets the limit to os.availableParallelism(), which generally corresponds to the number of available logical CPUs.

• A value of "unbounded" allows all scripts to run in parallel, but use this with caution, as it can overwhelm a machine and cause instability.

• A percentage value sets the limit to the percentage of os.availableParallelism(). Setting the max to 50% then sets the limit to roughly half of the available logical CPUs. Note that the limit is floored to the nearest integer.

Default Limit#

A value of "default" explicitly references the default limit.

When the environment variable BW_PARALLEL_MAX_DEFAULT is not set, it is equal to "auto". You can set BW_PARALLEL_MAX_DEFAULT to any of the valid values listed above.

Examples#

CLI:#

# Run in parallel (default is "auto" or value of BW_PARALLEL_MAX_DEFAULT env var)
bw run my-script --parallel

# Same as the above command
bw run my-script --parallel=default

# Run in parallel with a max of the available logical CPUs
bw run my-script --parallel=auto

# Run in parallel with a max of 2 concurrent scripts
bw run my-script --parallel=2

# Run in parallel with a max of 50% of the available logical CPUs
bw run my-script --parallel=50%

# Run every script in parallel (use with caution)
bw run my-script --parallel=unbounded

API:#

// Run in parallel with the default limit 
// Equal to "auto" or value of process.env.BW_PARALLEL_MAX_DEFAULT
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: true,
});

// Same result as above
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: { max: "default" },
});

// Run in parallel with the number of available logical CPUs
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: { max: "auto" },
});

// Run in parallel with a max of 50% of the available logical CPUs
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: { max: "50%" },
});

// Run in parallel with no concurrency limit (use with caution)
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: { max: "unbounded" },
});

// Run in parallel with a max of 2 concurrent scripts
project.runScriptAcrossWorkspaces({
  workspacePatterns: ["*"],
  script: "my-script",
  parallel: { max: 2 },
});