* Init should take a list of peers
This commit adds `--peers` option to `ipfs-cluster-service init`
`ipfs-cluster-service init --peers <multiaddress,multiaddress>`
- Adds and writes the given peers to the peerstore file
- For raft config section, adds the peer IDs to the `init_peerset`
- For crdt config section, add the peer IDs to the `trusted_peers`
Currently, unless doing Join() (--bootstrap), we do not connect to any peers on startup.
We however loaded up the peerstore file and Raft will automatically connect
older peers to figure out who is the leader etc. DHT bootstrap, after Raft
was working, did the rest.
For CRDTs we need to connect to people on a normal boot as otherwise, unless
bootstrapping, this does not happen, even if the peerstore contains known peers.
This introduces a number of changes:
* Move peerstore file management back inside the Cluster component, which was
already in charge of saving the peerstore file.
* We keep saving all "known addresses" but we load them with a non permanent
TTL, so that there will be clean up of peers we're not connected to for long.
* "Bootstrap" (connect) to a small number of peers during Cluster component creation.
* Bootstrap the DHT asap after this, so that other cluster components can
initialize with a working peer discovery mechanism.
* CRDT Trust() method will now:
* Protect the trusted Peer ID in the conn manager
* Give top priority in the PeerManager to that Peer (see below)
* Mark addresses as permanent in the Peerstore
The PeerManager now attaches priorities to peers when importing them and is
able to order them according to that priority. The result is that peers with
high priority are saved first in the peerstore file. When we load the peerstore
file, the first entries in it are given the highest priority.
This means that during startup we will connect to "trusted peers" first
(because they have been tagged with priority in the previous run and saved at
the top of the list). Once connected to a small number of peers, we let the
DHT bootstrap process in the background do the rest and discover the network.
All this makes the peerstore file a "bootstrap" list for CRDTs and we will attempt
to connect to peers on that list until some of those connections succeed.
This commit promotes the Consensus component (and Raft) to become a fully
independent thing like other components, passed to NewCluster during
initialization. Cluster (main component) no longer creates the consensus
layer internally. This has triggered a number of breaking changes
that I will explain below.
Motivation: Future work will require the possibility of running Cluster
with a consensus layer that is not Raft. The "consensus" layer is in charge
of maintaining two things:
* The current cluster peerset, as required by the implementation
* The current cluster pinset (shared state)
While the pinset maintenance has always been in the consensus layer, the
peerset maintenance was handled by the main component (starting by the "peers"
key in the configuration) AND the Raft component (internally)
and this generated lots of confusion: if the user edited the peers in the
configuration they would be greeted with an error.
The bootstrap process (adding a peer to an existing cluster) and configuration
key also complicated many things, since the main component did it, but only
when the consensus was initialized and in single peer mode.
In all this we also mixed the peerstore (list of peer addresses in the libp2p
host) with the peerset, when they need not to be linked.
By initializing the consensus layer before calling NewCluster, all the
difficulties in maintaining the current implementation in the same way
have come to light. Thus, the following changes have been introduced:
* Remove "peers" and "bootstrap" keys from the configuration: we no longer
edit or save the configuration files. This was a very bad practice, requiring
write permissions by the process to the file containing the private key and
additionally made things like Puppet deployments of cluster difficult as
configuration would mutate from its initial version. Needless to say all the
maintenance associated to making sure peers and bootstrap had correct values
when peers are bootstrapped or removed. A loud and detailed error message has
been added when staring cluster with an old config, along with instructions on
how to move forward.
* Introduce a PeerstoreFile ("peerstore") which stores peer addresses: in
ipfs, the peerstore is not persisted because it can be re-built from the
network bootstrappers and the DHT. Cluster should probably also allow
discoverability of peers addresses (when not bootstrapping, as in that case
we have it), but in the meantime, we will read and persist the peerstore
addresses for cluster peers in this file, different from the configuration.
Note that dns multiaddresses are now fully supported and no IPs are saved
when we have DNS multiaddresses for a peer.
* The former "peer_manager" code is now a pstoremgr module, providing utilities
to parse, add, list and generally maintain the libp2p host peerstore, including
operations on the PeerstoreFile. This "pstoremgr" can now also be extended to
perform address autodiscovery and other things indepedently from Cluster.
* Create and initialize Raft outside of the main Cluster component: since we
can now launch Raft independently from Cluster, we have more degrees of
freedom. A new "staging" option when creating the object allows a raft peer to
be launched in Staging mode, waiting to be added to a running consensus, and
thus, not electing itself as leader or doing anything like we were doing
before. This additionally allows us to track when the peer has become a
Voter, which only happens when it's caught up with the state, something that
was wonky previously.
* The raft configuration now includes an InitPeerset key, which allows to
provide a peerset for new peers and which is ignored when staging==true. The
whole Raft initialization code is way cleaner and stronger now.
* Cluster peer bootsrapping is now an ipfs-cluster-service feature. The
--bootstrap flag works as before (additionally allowing comma-separated-list
of entries). What bootstrap does, is to initialize Raft with staging == true,
and then call Join in the main cluster component. Only when the Raft peer
transitions to Voter, consensus becomes ready, and cluster becomes Ready.
This is cleaner, works better and is less complex than before (supporting
both flags and config values). We also backup and clean the state whenever
we are boostrapping, automatically
* ipfs-cluster-service no longer runs the daemon. Starting cluster needs
now "ipfs-cluster-service daemon". The daemon specific flags (bootstrap,
alloc) are now flags for the daemon subcommand. Here we mimic ipfs ("ipfs"
does not start the daemon but print help) and pave the path for merging both
service and ctl in the future.
While this brings some breaking changes, it significantly reduces the
complexity of the configuration, the code and most importantly, the
documentation. It should be easier now to explain the user what is the
right way to launch a cluster peer, and more difficult to make mistakes.
As a side effect, the PR also:
* Fixes#381 - peers with dynamic addresses
* Fixes#371 - peers should be Raft configuration option
* Fixes#378 - waitForUpdates may return before state fully synced
* Fixes#235 - config option shadowing (no cfg saves, no need to shadow)
License: MIT
Signed-off-by: Hector Sanjuan <code@hector.link>
