It has become increasingly common for major providers to experience outages—from Git servers being unavailable to failures when downloading external dependencies.
There are several ways to work around this, such as internal mirrors, vendoring dependencies, and similar approaches. While effective, these solutions can feel somewhat heavy-handed.
Bazel Remote Asset API
The Bazel Remote Asset API provides a mechanism for managing external dependencies in a centralized way.
More precisely, it maps external resource identifiers (such as URLs or Git repositories) to content stored in a content-addressable storage (CAS). ([DeepWiki][1])
In practice, this allows a server to:
- Fetch external resources (e.g. tarballs, Git repos)
- Store them in CAS
- Serve them to clients by digest
When used via Bazel’s remote downloader, this effectively acts as a download proxy/cache: instead of every developer machine and CI runner downloading dependencies independently, requests go through a central service that can fetch and cache them once.
How to Use
Getting started is straightforward: pass
--experimental_remote_downloader=SERVER_ADDRESS
either on the command line or in your .bazelrc.
This configures Bazel to route external downloads through a Remote Asset API–compatible service.
Before using it, ensure your remote cache/server supports the API. Many commercial solutions do, and the popular open-source bazel-remote supports (a subset of) it as well—though support is still marked experimental.
A Note on the Experimental Flag
Although the flag is prefixed with experimental, the feature has been available for some time and is widely used in practice. There is some good info on the Bazel Slack about it.
Conclusion
Combined with Bazel’s repository cache, the Remote Asset API provides a nice way to improve reliability when fetching external repos. It reduces reliance on third-party availability while avoiding the operational overhead of fully vendoring or mirroring all dependencies.