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Co-authored-by: Fabian Kammel <fabian@kammel.dev> Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>
39 lines
1.8 KiB
Markdown
39 lines
1.8 KiB
Markdown
# Bootstrapper
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The bootstrapper integrates the instance it is running on as node into the Kubernetes
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cluster. It is running on every new instance that is created.
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The bootstrapper has two active components:
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## Init Flow
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The InitServer is a gRPC server that is listining for initialization requests.
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The first instance needs to be initialized by the user, see the [initproto](./initproto)
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for a description of the initialization protocol. The client that talks to this server
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is part of Constellation's CLI.
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On an initialization request, the InitServer initializes a new Kubernetes cluster, essentially
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calling the InitCluster function of our Kubernetes library, which does a `kubeadm init`.
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## Join Flow
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The JoinClient is a gRPC client that tries to connect to a JoinService of an already existing cluster.
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The JoinService validates the instance using [aTLS](./../internal/atls/README.md).
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For details on the used protocol, see the [joinservice](./../joinservice) package.
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If the JoinService successfully verifies the instance, it issues a join ticket. The JoinClient then
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joins the cluster by calling the `kubeadm join` command, using the token and other needed information
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from the join ticket.
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## Synchronization, state machine, lifetime
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The bootstrapper is automatically started on every new instance. Both InitServer and JoinClient are
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started and running in parallel. At some point during either the initialization or the join, a shared
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lock between the two components is acquired. This lock is used as point of no return. It is a state
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machine with two states (unlocked, locked) and a single transition from unlocked to locked. There is no
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way to unlock the node afterward (see [nodelock](./internal/nodelock) package).
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After the bootstrapping, the bootstrapper is stopped.
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