rstash is a ccache-like compiler caching tool. It is used as a compiler wrapper and avoids compilation when possible, storing cached results either on local disk or in one of several cloud storage backends.
rstash includes support for caching the compilation of C/C++ code, Rust, as well as NVIDIA's CUDA using nvcc, and clang.
rstash also provides icecream-style distributed compilation (automatic packaging of local toolchains) for all supported compilers (including Rust). The distributed compilation system includes several security features that icecream lacks such as authentication, transport layer encryption, and sandboxed compiler execution on build servers. See the distributed quickstart guide for more information.
rstash is also available as a GitHub Actions to facilitate the deployment using GitHub Actions cache.
- Installation
- Usage
- Build Requirements
- Build
- Separating caches between invocations
- Overwriting the cache
- Debugging
- Interaction with GNU
makejobserver - Known Caveats
- Storage Options
There are prebuilt x86-64 binaries available for Windows, Linux (a portable binary compiled against musl), and macOS on the releases page. Several package managers also include rstash packages, you can install the latest release from source using cargo, or build directly from a source checkout.
On macOS rstash can be installed via Homebrew:
brew install rstashor via MacPorts:
sudo port install rstashOn Windows, rstash can be installed via scoop:
scoop install rstash
If you have a Rust toolchain installed you can install rstash using cargo. Note that this will compile rstash from source which is fairly resource-intensive. For CI purposes you should use prebuilt binary packages.
cargo install rstash --lockedRunning rstash is like running ccache: prefix your compilation commands with it, like so:
rstash gcc -o foo.o -c foo.cIf you want to use rstash for caching Rust builds you can define build.rustc-wrapper in the
cargo configuration file. For example, you can set it globally
in $HOME/.cargo/config.toml by adding:
[build]
rustc-wrapper = "/path/to/rstash"Note that you need to use cargo 1.40 or newer for this to work.
Alternatively you can use the environment variable RUSTC_WRAPPER:
export RUSTC_WRAPPER=/path/to/rstash
cargo buildrstash supports gcc, clang, MSVC, rustc, NVCC, NVC++, and Wind River's diab compiler. Both gcc and msvc support Response Files, read more about their implementation here.
If you don't specify otherwise, rstash will use a local disk cache.
rstash works using a client-server model, where the server runs locally on the same machine as the client. The client-server model allows the server to be more efficient by keeping some state in memory. The rstash command will spawn a server process if one is not already running, or you can run rstash --start-server to start the background server process without performing any compilation.
By default rstash server will listen on 127.0.0.1:4226, you can specify environment variable RSTASH_SERVER_PORT to use a different port or RSTASH_SERVER_UDS to listen on unix domain socket. Abstract unix socket is also supported as long as the path is escaped following the format. For example:
% env RSTASH_SERVER_UDS=$HOME/rstash.sock rstash --start-server # unix socket
% env RSTASH_SERVER_UDS=\\x00rstash.sock rstash --start-server # abstract unix socket
You can run rstash --stop-server to terminate the server. It will also terminate after (by default) 10 minutes of inactivity.
Running rstash --show-stats will print a summary of cache statistics.
Some notes about using rstash with Jenkins are here.
To use rstash with cmake, provide the following command line arguments to cmake 3.4 or newer:
-DCMAKE_C_COMPILER_LAUNCHER=rstash
-DCMAKE_CXX_COMPILER_LAUNCHER=rstash
The process for using rstash with MSVC and cmake, depends on which version of cmake you're using. For versions of cmake 3.24 and earlier, to generate PDB files for debugging with MSVC, you can use the /Z7 option. Alternatively, the /Zi option together with /Fd can work if /Fd names a different PDB file name for each object file created. Note that CMake sets /Zi by default, so if you use CMake, you can use /Z7 by adding code like this in your CMakeLists.txt:
if(CMAKE_BUILD_TYPE STREQUAL "Debug")
string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG}")
string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG}")
elseif(CMAKE_BUILD_TYPE STREQUAL "Release")
string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
elseif(CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
string(REPLACE "/Zi" "/Z7" CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
string(REPLACE "/Zi" "/Z7" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO}")
endif()By default, rstash will fail your build if it fails to successfully communicate with its associated server. To have rstash instead gracefully failover to the local compiler without stopping, set the environment variable RSTASH_IGNORE_SERVER_IO_ERROR=1.
For versions of cmake 3.25 and later, to compile with MSVC, you have to use the new CMAKE_MSVC_DEBUG_INFORMATION_FORMAT option, meant to configure the -Z7 flag. Additionally, you must set the cmake policy number 0141 to the NEW setting:
set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT Embedded)
cmake_policy(SET CMP0141 NEW)Example configuration where we automatically look for rstash in the PATH:
find_program(RSTASH rstash REQUIRED)
set(CMAKE_C_COMPILER_LAUNCHER ${RSTASH})
set(CMAKE_CXX_COMPILER_LAUNCHER ${RSTASH})
set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT Embedded)
cmake_policy(SET CMP0141 NEW)Alternatively, if configuring cmake with MSVC on the command line, assuming that rstash is on the default search path:
cmake -DCMAKE_C_COMPILER_LAUNCHER=rstash -DCMAKE_CXX_COMPILER_LAUNCHER=rstash -DCMAKE_MSVC_DEBUG_INFORMATION_FORMAT=Embedded -DCMAKE_POLICY_CMP0141=NEW [...]
And you can build code as usual without any additional flags in the command line, which is useful for IDEs.
rstash is a Rust program. Building it requires cargo (and thusrustc). rstash currently requires Rust 1.75.0. We recommend you install Rust via Rustup.
If you are building rstash for non-development purposes make sure you use cargo build --release to get optimized binaries:
cargo build --release [--no-default-features --features=s3|redis|gcs|memcached|azure|gha|webdav|oss]The list of features can be found in the Cargo.toml file, [features] section.
By default, rstash builds with support for all storage backends, but individual backends may be disabled by resetting the list of features and enabling all the other backends. Refer the Cargo Documentation for details on how to select features with Cargo.
When building with the dist-server feature, rstash will depend on OpenSSL, which can be an annoyance if you want to distribute portable binaries. It is possible to statically link against OpenSSL using the openssl/vendored feature.
Build with cargo and use ldd to check that the resulting binary does not depend on OpenSSL anymore.
Build with cargo and use otool -L to check that the resulting binary does not depend on OpenSSL anymore.
On Windows, the binary might also depend on a few MSVC CRT DLLs that are not available on older Windows versions.
It is possible to statically link against the CRT using a .cargo/config.toml file with the following contents.
[target.x86_64-pc-windows-msvc]
rustflags = ["-Ctarget-feature=+crt-static"]Build with cargo and use dumpbin /dependents to check that the resulting binary does not depend on MSVC CRT DLLs anymore.
When statically linking with OpenSSL, you will need Perl available in your $PATH.
In situations where several different compilation invocations
should not reuse the cached results from each other,
one can set RSTASH_C_CUSTOM_CACHE_BUSTER to a unique value
that'll be mixed into the hash.
MACOSX_DEPLOYMENT_TARGET and IPHONEOS_DEPLOYMENT_TARGET variables
already exhibit such reuse-suppression behaviour.
There are currently no such variables for compiling Rust.
In situations where the cache contains broken build artifacts, it can be necessary to overwrite the contents in the cache. That can be achieved by setting the RSTASH_RECACHE environment variable.
You can set the RSTASH_ERROR_LOG environment variable to a path and set RSTASH_LOG to get the server process to redirect its logging there (including the output of unhandled panics, since the server sets RUST_BACKTRACE=1 internally).
RSTASH_ERROR_LOG=/tmp/rstash_log.txt RSTASH_LOG=debug rstash
You can also set these environment variables for your build system, for example
RSTASH_ERROR_LOG=/tmp/rstash_log.txt RSTASH_LOG=debug cmake --build /path/to/cmake/build/directory
Alternatively, if you are compiling locally, you can run the server manually in foreground mode by running RSTASH_START_SERVER=1 RSTASH_NO_DAEMON=1 rstash, and send logging to stderr by setting the RSTASH_LOG environment variable for example. This method is not suitable for CI services because you need to compile in another shell at the same time.
RSTASH_LOG=debug RSTASH_START_SERVER=1 RSTASH_NO_DAEMON=1 rstash
rstash provides support for a GNU make jobserver. When the server is started from a process that provides a jobserver, rstash will use that jobserver and provide it to any processes it spawns. (If you are running rstash from a GNU make recipe, you will need to prefix the command with + to get this behavior.) If the rstash server is started without a jobserver present it will create its own with the number of slots equal to the number of available CPU cores.
This is most useful when using rstash for Rust compilation, as rustc supports using a jobserver for parallel codegen, so this ensures that rustc will not overwhelm the system with codegen tasks. Cargo implements its own jobserver (see the information on NUM_JOBS in the cargo documentation) for rustc to use, so using rstash for Rust compilation in cargo via RUSTC_WRAPPER should do the right thing automatically.
- Absolute paths to files must match to get a cache hit. This means that even if you are using a shared cache, everyone will have to build at the same absolute path (i.e. not in
$HOME) in order to benefit each other. In Rust this includes the source for third party crates which are stored in$HOME/.cargo/registry/cacheby default.
- Crates that invoke the system linker cannot be cached. This includes
bin,dylib,cdylib, andproc-macrocrates. You may be able to improve compilation time of largebincrates by converting them to alibcrate with a thinbinwrapper. - Incrementally compiled crates cannot be cached. By default, in the debug profile Cargo will use incremental compilation for workspace members and path dependencies. You can disable incremental compilation.
- Symbolic links to rstash won't work. Use hardlinks:
ln rstash /usr/local/bin/cc
- Requests sent to your storage option of choice will have a user agent header indicating the current rstash version, e.g.
rstash/0.8.2.