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Peter Goodspeed-Niklaus 28ad9997ea Automatic Example Collator (#67 )

* add polkadot build script

* Add scripting to bring up a simple alice-bob example net

Demonstrated to produce blocks, but as of right now there's still
trouble getting it to respond to external queries on its ports.

* enable external rpc access to the nodes

Also shrink the build context by excluding some extraneous data.

* Ensure external RPC access works

Also set default branch appropriately, and have the stop command
clean itself up more thoroughly.

* Add multi-stage dockerfile for building the cumulus-test-parachain-collator

- Exclude the docker/ directory from build context because we're
never going to build recursively, and this prevents spurious
cache misses
- build the parachain collator in three stages. The build stage
is discarded; the collator stage has a wrapper script to simplify
generating the right bootnodes flags, and the default stage
has just the binary in a small runtime.
- build_collator.sh collects appropriate build flags for the dockerfile
- inject_bootnodes.sh discovers the testnet node IDs and inserts them
into the arguments list for cumulus-test-parachain-collator

* Add services which generate genesis state, run the collator

- Ignore the scripts directory to reduce spurious cache misses.
- Move inject_bootnodes.sh from the scripts directory into the root:
It can't stay in the scripts directory, because that's ignored;
I didn't want to invent _another_ top-level subdirectory for it.
That decision could certainly be appealed, though.
- Move docker-compose.yml, add dc.sh, modify *_collator.sh: by
taking docker-compose.yml out of the root directory, we can
further reduce cache misses. However, docker-compose normally
has a strong expectation that docker-compose.yml exist in the
project root; it takes a moderately complicated invocation to
override that expectation. That override is encoded in dc.sh;
the updates to the other scripts are just to use the override.

The expectation as of now is that scripts/run_collator.sh runs
both chain nodes and the collator, generates the genesis state
into a volume with a transient container, and runs the collator
as specified in the repo README.

Upcoming work: Steps 5 and 6 from the readme.

* Launch the collator node

The biggest change here is adding the testing_net network to the
collator node's networks list. This lets it successfully connect
to the alice and bob nodes, which in turn lets it get their node IDs,
which was the blocker for a long time.

Remove httpie in favor of curl: makes for a smaller docker image,
and has fewer weird failure modes within docker.

Unfortunately this doesn't yet actually connect to the relay chain
nodes; that's the next area to figure out.

* enable external websocket access to indexer nodes

* Reorganize for improved caching, again

- Manually enumerate the set of source directories to copy when building.
This bloats the cache a bit, but means that rebuilds on script changes
don't bust that cache, which saves a _lot_ of time.
- Un-.dockerignore the scripts directory; it's small and will no longer
trigger cache misses.
- Move inject_bootnodes.sh back into scripts directory for better organization.
- inject_bootnodes.sh: use rpc port for rpc call and p2p port for
generating the bootnode string. I'm not 100% sure this is correct,
but upwards of 80% at least.
- docker-compose.yml: reorganize the launch commands such that alice
and bob still present the same external port mapping to the world,
but within the docker-compose network, they both use the same
(standard) p2p, rpc, and websocket ports. This makes life easier
for inject_bootnodes.sh

The collator node still doesn't actually connect, but I think this
commit still represents real progress in that direction.

* Get the collator talking to the indexer nodes

In the end, it was four characters: -- and two = signs in the
launch arguments. They turn out to be critical characters for
correct operation, though!

Next up: automating step 5.

* Add runtime stage to collect runtime wasm blob into volume

We can't just copy the blob in the builder stage because the volumes
aren't available at that point.

Rewrite build_collator.sh into build_docker.sh and update for generality.

* WIP: add registrar service and partial work to actually register the collator

This is likely to be discarded; the Python library in use is 3rd party
and not well documented, while the official polkadot-js repo has a
CLI tool: https://github.com/polkadot-js/tools/tree/master/packages/api-cli

* Add a parachain registrar which should properly register the parachain

Doesn't work at the moment because it depends on two api-cli features
which I added today, which have not yet made it out into a published
release.

Next up: figure out how to add the `api-cli` at its `master` branch,
then run tests to ensure the collator is producing blocks. Then,
automate the block production tests.

* BROKEN attempt to demo registrar communication with the blockchain

This is a really weird bug. After running `scripts/run_collector.sh`,
which brings everything up, it's perfectly possible to get into
a state very much like what the registrar is in, and communicate
with the blockchain without issue:

```sh
$ docker run --rm --net cumulus_testing_net para-reg:latest polkadot-js-api --ws ws://172.28.1.1:9944 query.sudo.key
Thu 20 Feb 2020 12:19:20 PM CET
{
"key": "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY"
}
```

However, the registrar itself, doing the same thing from within
`register_para.sh`, is failing to find the right place in the network:

```
/runtime/cumulus_test_parachain_runtime.compact.wasm found after 0 seconds
/genesis/genesis-state found after 0 seconds
2020-02-20 10:43:22 API-WS: disconnected from ws://172.28.1.1:9944 code: '1006' reason: 'connection failed'
_Event {
type: 'error',
isTrusted: false,
_yaeti: true,
target: W3CWebSocket {
_listeners: {},
addEventListener: [Function: _addEventListener],
removeEventListener: [Function: _removeEventListener],
dispatchEvent: [Function: _dispatchEvent],
_url: 'ws://172.28.1.1:9944',
_readyState: 3,
_protocol: undefined,
_extensions: '',
_bufferedAmount: 0,
_binaryType: 'arraybuffer',
_connection: undefined,
_client: WebSocketClient {
_events: [Object: null prototype] {},
_eventsCount: 0,
_maxListeners: undefined,
config: [Object],
_req: null,
protocols: [],
origin: undefined,
url: [Url],
secure: false,
base64nonce: 'aJ6J3pYDz8l5owVWHGbzHg==',
[Symbol(kCapture)]: false
},
onclose: [Function (anonymous)],
onerror: [Function (anonymous)],
onmessage: [Function (anonymous)],
onopen: [Function (anonymous)]
},
cancelable: true,
stopImmediatePropagation: [Function (anonymous)]
}
```

They should be connected to the same network, running the same
image, doing the same call. The only difference is the file
existence checks, which really shouldn't be affecting the network
state at all.

Pushing this commit to ask for outside opinions on it, because
this is very weird and I clearly don't understand some part of
what's happening.

* Fix broken parachain registrar

The problem was that the registrar container was coming up too fast,
so the Alice node wasn't yet ready to receive connections. Using
a well-known wait script fixes the issue.

Next up: verify that the collator is in fact building blocks.

* fixes which cause the collator to correctly produce new parachain blocks

It didn't take much! The biggest issue was that the genesis state
was previously being double-encoded.

* add documentation for running the parachain automatically

* Add health check to collator

* minor scripting improvements

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Docker: copy the whole workspace in one go

Pro: future-proofing against the time we add or remove a directory
Con: changing any file in the workspace busts Rust's build cache,
which takes a long time.

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

2020-02-21 16:20:22 +01:00

4.2 KiB

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Cumulus

A set of tools for writing Polkadot parachains that are based on Substrate.

It's easy to write blockchains using Substrate, and the overhead of writing parachains' distribution, p2p, database, and synchronization layers is generally high and should be reusable. This project aims to make it easy to write parachains for Polkadot by leveraging the power of Substrate.

Cumulus clouds are shaped sort of like dots and are up in the air, like this project (as it is an initial prototype -- expect a rename when it gets cooler.)

cumulus-consensus

For now, this is only project contained in this repo. cumulus-consensus is a consensus engine for Substrate which follows a Polkadot relay chain. This will run a Polkadot node internally, and dictate to the client and synchronization algorithms which chain to follow, finalize, and treat as best.

cumulus-runtime

A planned wrapper around substrate runtimes to turn them into parachain validation code and to provide proof-generation routines.

cumulus-collator

A planned Polkadot collator for the parachain.

Running a collator

Checkout polkadot at 96f5dc510ef770fd5c5ab57a90565bb5819bbbea.
Run Alice and Bob:

cargo run --release -- --chain=${CUMULUS_REPO}/test/parachain/res/polkadot_chainspec.json --base-path=cumulus_relay_chain_node_0 --alice

cargo run --release -- --chain=${CUMULUS_REPO}/test/parachain/res/polkadot_chainspec.json --base-path=cumulus_relay_chain_node_1 --bob --port 50666

Where CUMULUS_REPO is the path to the checkout of Cumulus.
Switch back to this repository and generate the parachain genesis state:

cargo run --release -p cumulus-test-parachain-collator -- export-genesis-state genesis-state
Run the collator:

cargo run --release -p cumulus-test-parachain-collator -- --base-path cumulus_collator_path -- --bootnodes=/ip4/127.0.0.1/tcp/30333/p2p/PEER_ID_${NAME} --bootnodes=/ip4/127.0.0.1/tcp/50666/p2p/PEER_ID_${NAME}

PEER_ID_${NAME} needs to be replaced with the peer id of the polkadot validator that uses ${NAME} as authority. The -- after --base-path cumulus_collator_path is important, it tells the CLI to pass these arguments to the relay chain node that is running inside of the collator.
Open https://polkadot.js.org/apps/#/sudo and register the parachain by calling Registrar > RegisterPara

id: 100

ParaInfo: Always

code: CUMULUS_REPO/target/release/wbuild/cumulus-test-parachain-runtime/cumulus_test_parachain_runtime.compact.wasm

initial_head_data: Use the file you generated in step 3. (name: genesis-state)

Now your parachain should be registered and the collator should start building blocks and sending them to the relay chain.
Now the collator should build blocks and the relay-chain should include them. You can check that the parachain-header for parachain 100 is changing.

Running the collator automatically

To simplify the above process, you can run steps 1-5 above automatically:

export BRANCH=96f5dc510ef770fd5c5ab57a90565bb5819bbbea
scripts/build_polkadot.sh
scripts/run_collator.sh

This will churn for several minutes, but should end with docker reporting that several containers have successfully been brought up.

To run step 6, first set up an alias which gives you quick access to the polkadot-js CLI:

docker build -f docker/parachain-registrar.dockerfile --target pjs -t parachain-registrar:pjs .
alias pjs='docker run --rm --net cumulus_testing_net parachain-registrar:pjs --ws ws://172.28.1.1:9944'

Those steps should complete very quickly. At that point, you can do things like:

$ pjs query.parachains.heads 100
{
  "heads": "0xe1efbf8cc2e1304da927986f4cd6964ce0888ce3995948bf71fe427b1a9d39b02101d2dac9c5342d7e8c4f4de2f5277ef860b3a518c1cd823b9a8cee175dce11bf7f57c5016e8a60a6cec16244b2cbf81a67a1dc7a825c288fc694997bc70e2d456400"
}

The collator includes its own health check, which you can inspect with

docker inspect --format='{{json .State.Health}}' cumulus_collator_1

The check runs every 5 minutes, and takes about a minute to complete each time. Most of that time is spent sleeping; it remains a very lightweight process.

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