Terragrunt is running slowly. How do I speed it up?

Most slow runs come down to doing work you did not need to do: running units that did not change, downloading the same provider once per unit, or initializing dependencies just to read their outputs. The Performance guide covers this in full. The short version:

Run fewer units

The largest win is usually running less. The --filter flag restricts a run to the units you care about, and git-based filters restrict it to the units a diff touched. --filter-affected is the shorthand for the common case, comparing your repository’s default branch against HEAD:

terragrunt run --all --filter-affected -- plan

It compares committed changes, so uncommitted work in progress may not be picked up. Terragrunt logs a warning when it notices local modifications.

Share provider downloads

Providers are large binaries, and without a shared cache every unit downloads its own copy. On OpenTofu 1.10 and later this is already handled: Automatic Provider Cache Dir is on by default and points OpenTofu at a shared cache directory, with nothing for you to enable.

Reach for the Provider Cache Server when that default does not apply or does not scale, which the docs narrow to four cases: you use Terraform, you use an older OpenTofu, your cache lives on an NFS mount, or you are large enough that filesystem lock contention on the cache directory has become the bottleneck.

terragrunt run --all --provider-cache -- plan

The cache server is built for runs that do many OpenTofu/Terraform operations at once, so pair it with --all. On a single-unit run it can cost more than it saves, because starting and stopping the server may outweigh the downloads it avoids.

Stop initializing dependencies to read outputs

By default, Terragrunt runs output -json against each dependency, which loads providers it does not need. The dependency-fetch-output-from-state experiment reads the values straight out of the state file instead:

terragrunt run --all --experiment=dependency-fetch-output-from-state -- plan

This only applies to S3 backends, and it fails outright with OpenTofu client-side state encryption, since Terragrunt cannot parse an encrypted state file. See the gotchas before turning it on.

Cache repository clones

If many units source modules from the same git repository, the Content Addressable Store clones it once and reuses it. This is on by default as of 1.1. On earlier versions, enable it with --experiment cas.

Measure before you tune

Guessing at the bottleneck wastes time. Terragrunt emits OpenTelemetry traces, so you can see where a run spends its time:

export TG_TELEMETRY_TRACE_EXPORTER=http
export TG_TELEMETRY_TRACE_EXPORTER_HTTP_ENDPOINT=localhost:4318
export TG_TELEMETRY_TRACE_EXPORTER_INSECURE_ENDPOINT=true

Point those at a local collector such as Jaeger and read the trace. Tuning parallelism is worth reaching for only once you know parallelism is the constraint. Raising --parallelism on a run that is bottlenecked on provider downloads makes things worse, not better.

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