.. _cache_servers: Configuring Cache Servers ========================= BuildStream caches the results of builds in a local artifact cache, and will avoid building an element if there is a suitable build already present in the local artifact cache. Similarly it will cache sources and avoid pulling them if present in the local cache. See :ref:`caches ` for more details. In addition to the local caches, you can configure one or more remote caches and BuildStream will then try to pull a suitable object from one of the remotes, falling back to performing a local build or fetching a source if needed. Configuring BuildStream to use remote caches -------------------------------------------- A project will often set up continuous build infrastructure that pushes cached objects to a shared cache, so developers working on the project can make use of these pre-made objects instead of having to each build the whole project locally. The project can declare this cache in its project configuration file for :ref:`artifacts ` and :ref:`sources `. Users can declare additional remote caches in the :ref:`user configuration `. There are several use cases for this: your project may not define its own cache, it may be useful to have a local mirror of its cache, or you may have a reason to share artifacts privately. Remote caches are identified by their URL. There are currently two supported protocols: * ``http``: Pull and push access, without transport-layer security * ``https``: Pull and push access, with transport-layer security BuildStream allows you to configure as many caches as you like, and will query them in a specific order: 1. Project-specific overrides in the user config 2. Project configuration 3. User configuration When an an object is created locally, BuildStream will try to push it to all the caches which have the ``push: true`` flag set. You can also manually push artifacts to a specific cache using the :ref:`bst artifact push command `. Objects are identified using the element or sources :ref:`cache key ` so the objects provided by a cache should be interchangable with those provided by any other cache. Setting up a remote cache ------------------------- The rest of this page outlines how to set up a shared cache. Setting up the user ~~~~~~~~~~~~~~~~~~~ A specific user is not needed, however, a dedicated user to own the cache is recommended. .. code:: bash useradd artifacts The recommended approach is to run two instances on different ports. One instance has push disabled and doesn't require client authentication. The other instance has push enabled and requires client authentication. Alternatively, you can set up a reverse proxy and handle authentication and authorization there. Installing the server ~~~~~~~~~~~~~~~~~~~~~ You will also need to install BuildStream on the cache server in order to receive uploaded artifacts over ssh. Follow the instructions for installing BuildStream `here `_. When installing BuildStream on the cache server, it must be installed in a system wide location, with ``pip3 install .`` in the BuildStream checkout directory. Otherwise, some tinkering is required to ensure BuildStream is available in ``PATH`` when its companion ``bst-artifact-server`` program is run remotely. You can install only the artifact server companion program without requiring BuildStream's more exigent dependencies by setting the ``BST_ARTIFACTS_ONLY`` environment variable at install time, like so: .. code:: BST_ARTIFACTS_ONLY=1 pip3 install . .. _artifact_command_reference: Command reference ~~~~~~~~~~~~~~~~~ .. click:: buildstream._cas.casserver:server_main :prog: bst-artifact-server .. _server_authentication: Key pair for the server ~~~~~~~~~~~~~~~~~~~~~~~ For TLS you need a key pair for the server. The following example creates a self-signed key, which requires clients to have a copy of the server certificate (e.g., in the project directory). You can also use a key pair obtained from a trusted certificate authority instead. .. code:: bash openssl req -new -newkey rsa:4096 -x509 -sha256 -days 3650 -nodes -batch -subj "/CN=artifacts.com" -out server.crt -keyout server.key .. note:: Note that in the ``-subj "/CN="`` argument, ``/CN`` is the *certificate common name*, and as such ```` should be the public hostname of the server. IP addresses will **not** provide you with working authentication. In addition to this, ensure that the host server is recognised by the client. You may need to add the line: ```` ```` to your ``/etc/hosts`` file. Authenticating users ~~~~~~~~~~~~~~~~~~~~ In order to give permission to a given user to upload artifacts, create a TLS key pair on the client. .. code:: bash openssl req -new -newkey rsa:4096 -x509 -sha256 -days 3650 -nodes -batch -subj "/CN=client" -out client.crt -keyout client.key Copy the public client certificate ``client.crt`` to the server and then add it to the authorized keys, like so: .. code:: bash cat client.crt >> /home/artifacts/authorized.crt Serve the cache over https ~~~~~~~~~~~~~~~~~~~~~~~~~~ Public instance without push: .. code:: bash bst-artifact-server --port 11001 --server-key server.key --server-cert server.crt /home/artifacts/artifacts Instance with push and requiring client authentication: .. code:: bash bst-artifact-server --port 11002 --server-key server.key --server-cert server.crt --client-certs authorized.crt --enable-push /home/artifacts/artifacts .. note:: BuildStream's artifact cache uses `Bazel's Remote Execution CAS and Remote Asset API `_. Sometimes, when using Remote Execution, it is useful to run BuildStream with just a basic CAS server, without using the Remote Asset API, but BuildStream still needs to store these to work correctly. For this scenario, you can add the `--index-only` flag to the above commands, and configure BuildStream to store artifact metadata and files in a separate caches (e.g. bst-artifact-server and Buildbarn) using :ref:`"types" `. Managing the cache with systemd ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We recommend running the cache as a systemd service, especially if it is running on a dedicated server, as this will allow systemd to manage the cache, in case the server encounters any issues. Below are two examples of how to run the cache server as a systemd service. The first, is for pull only and the other is configured for push & pull. Notice that the two configurations use different ports. ``bst-artifact-serve.service``: .. code:: ini # # Pull # [Unit] Description=Buildstream Artifact pull server After=remote-fs.target network-online.target [Service] Environment="LC_ALL=C.UTF-8" ExecStart=/usr/local/bin/bst-artifact-server --port 11001 --server-key {{certs_path}}/server.key --server-cert {{certs_path}}/server.crt {{artifacts_path}} User=artifacts [Install] WantedBy=multi-user.target ``bst-artifact-serve-receive.service``: .. code:: ini # # Pull/Push # [Unit] Description=Buildstream Artifact pull/push server After=remote-fs.target network-online.target [Service] Environment="LC_ALL=C.UTF-8" ExecStart=/usr/local/bin/bst-artifact-server --port 11002 --server-key {{certs_path}}/server.key --server-cert {{certs_path}}/server.crt --client-certs {{certs_path}}/authorized.crt --enable-push {{artifacts_path}} User=artifacts [Install] WantedBy=multi-user.target Here we define when systemd should start the service, which is after the networking stack has been started, we then define how to run the cache with the desired configuration, under the artifacts user. The {{ }} are there to denote where you should change these files to point to your desired locations. .. note:: You may need to run some of the following commands as the superuser. These files should be copied to ``/etc/systemd/system/``. We can then start these services with: .. code:: bash systemctl enable bst-artifact-serve.service systemctl enable bst-artifact-serve-receive.service Then, to start these services: .. code:: bash systemctl start bst-artifact-serve.service systemctl start bst-artifact-serve-receive.service We can then check if the services are successfully running with: .. code:: bash journalctl -u bst-artifact-serve.service journalctl -u bst-artifact-serve-receive.service For more information on systemd services see: `Creating Systemd Service Files `_. Declaring remote caches ~~~~~~~~~~~~~~~~~~~~~~~ Remote caches can be declared within either: 1. The project configuration for :ref:`artifact ` and :ref:`sources `, or 2. The user configuration for :ref:`artifacts ` and :ref:`sources `. Please follow the above links to see examples showing how we declare remote caches in both the project configuration and the user configuration, respectively.