Nimbus `v1.5.5` is a `medium-urgency` bugfix release which contains a number of significant optimisations; of particular note is a **6x speed-up in epoch processing** and **2x speed up in Altair block processing**.
In addition, `v1.5.5` adds support for the `web3signer` protocol (currently in BETA).
### We've fixed:
* The potential for missed block proposals when a third-party validator client (with at least one imported validator) is used with a Nimbus beacon node (with no imported validators)
* The web3 connection not being enabled when running third-party validator clients
* A rare condition in which the REST service becomes unavailable.
* Inappropriate error messages produced by the REST API: when a validator client is publishing the same attestations or sync committee messages through multiple beacon nodes.
### Improvements:
* 6x speed-up in epoch processing: https://github.com/status-im/nimbus-eth2/pull/3089
* 2x speed up in Altair block processing: https://github.com/status-im/nimbus-eth2/pull/3115
* A 12% (minimum) reduction in the outgoing GossipSub traffic: https://github.com/status-im/nimbus-eth2/pull/3112
* Across the board performance improvements in the REST API: https://github.com/status-im/nimbus-eth2/pull/3092
* The REST API can now report sync committee information for the next sync period: https://github.com/status-im/nimbus-eth2/pull/3133
* Added support for the web3signer protocol (beta release):
Nimbus `v1.5.4` is a `medium-urgency` hotfix release. It addresses an important issue which, in rare cases, can lead to the loss of attestations and sync committee messages. This can, in turn, lead to a reduction in rewards.
* A rare issue during the construction of sync committee contributions: invalid BLS aggregate signatures were being produced under certain conditions; this had the potential to negatively affect the peer score of the node, and impact its ability to deliver gossip messages.
* A non-spec-compliant implementation of the `/eth/v1/validator/duties/sync/{epoch}` REST API.
* A crash in the `/eth/v2/debug/beacon/states` REST API call on systems with limited stack space.
### Improvements:
* A nice little performance improvement for block verification and replay.
* Improved error messages in the REST API.
* The `/eth/v1/config/spec` REST API now returns more information regarding spec config parameters.
## Other notable changes:
* The `--log-file` option is now deprecated and may be removed in a future release (if you wish to log to a file, we recommend redirecting the standard output).
Please note that the --log-file option was previously supported only when Nimbus was built from source. If your existing configuration used the --log-file option with a binary release, upgrading to v1.5.4 will enable the log file creation (though a deprecation warning will be printed on start-up).
Nimbus `v1.5.1` is a `high-urgency` release for all users who have already upgraded to `v1.5.0`. It fixes a deposit contract syncing issue manifesting as the warning message "Eth1 chain not synced". Under specific circumstances, such a failure to sync the Eth1 chain may result in missed Eth2 block proposals, so affected users are advised to upgrade as soon as possible.
For anyone still running Nimbus v1.4.x or earlier, migrating to v1.5.1 continues to be a `medium-urgency` but *mandatory* upgrade that must be installed **before October 27th**.
Nimbus `v1.5.0` is a `medium-urgency` but *mandatory* upgrade which adds support for the upcoming beacon chain Altair hard-fork.
Please upgrade at your earliest convenience - **before the 27th of October**.
> **N.B** You must upgrade before October 27th in order to follow the mainnet beacon chain. Failure to do so will result in downtime penalties.
This is the first hard fork for the beacon chain, and while a significant amount of testing has been conducted in the run up to this release, we recommend users regularly monitor our announcement channels ([discord]() and/or the [newsletter]()) for potential updates.
To celebrate the feature complete release candidate of our REST API, we've opened up the ports on some of our fleet nodes - don't do this at home ;)
In order to interact with these, you should point your apps and tools to:
* http://unstable.mainnet.beacon-api.nimbus.team/ - `mainnet` data, the latest `unstable` [branch](https://github.com/status-im/nimbus-eth2/tree/unstable)
* http://unstable.prater.beacon-api.nimbus.team/ - `prater` testnet data, the [latest](http://unstable.mainnet.beacon-api.nimbus.team/eth/v1/node/version) `unstable` [branch](https://github.com/status-im/nimbus-eth2/tree/unstable)
Note that right now these are very much unstable testing instances. They may be unresponsive at times - so **please do not rely on them for validation**. We may also disable them at any time.
--------------
### Notable changes
* Support for the Altair hard fork and the [latest Ethereum consensus spec](https://github.com/ethereum/consensus-specs/releases/tag/v1.1.1) (`v1.1.1`)
* Our [REST API](https://nimbus.guide/rest-api.html) is now feature complete, supporting the full [Beacon API](https://ethereum.github.io/beacon-APIs/) specification. This API should not be exposed to the public Internet as it includes multiple endpoints which could open your node to denial-of-service (DoS) attacks.
* Known limitations: To use the REST API with a validator client, you need to enable the `--subscribe-all-subnets` option. This requirement will be removed in future versions.
* A new experimental `--num-threads=X` option allows Nimbus to take advantage of multiple CPU cores when verifying attestations. Set it to `1` to use one worker thread, `2` for two worker threads, etc. The default value is set to `1` in this release, but future versions will set it to `0` (this tells the client to use as many worker threads as there are CPU cores available). N.B .**enabling anything other than `1` is considered experimental** at this stage.
* Improved peer discovery logic that ensures good connectivity to all gossip subnets.
* A new `version` metric that makes it easy to keep track of client upgrades within Grafana dashboards.
* New metrics `libp2p_peers_identity`, `libp2p_peers_traffic_read_total`, `libp2p_peers_traffic_write_total`, subdivided through Prometheus labels by the client type of the peer (i.e. nimbus, prysm, teku, lodestar or lighthouse).
* BLST has been upgraded to the latest version (`v0.3.5`).
* The `--network` option now accepts a directory with custom network metadata in the format of the [eth2-testnets](https://github.com/eth2-clients/eth2-networks) repository. The `SECONDS_PER_SLOT` configuration value remains the only setting that must be supplied at compile-time through the `-d:SECONDS_PER_SLOT=X` nim compilation flag.
This release is marked as `low-urgency` for all Nimbus users other than those who have recently updated to `v1.4.1` from a version earlier than `v1.1.0` - for these users this is a `high-urgency` release.
## Notable changes
This release fixes an issue in the upgrade procedure when upgrading from a version earlier than `1.1.0` to `1.4.x`.
**How can I tell if I've been affected?**
If you've already upgraded to `1.4.1`, you can tell that you've been affected if you're seeing the following` WRN log`:
```
Received invalid sequence of blocks
```
To re-iterate, this issue only affects users who are upgrading from `1.0.12` or earlier (released on `2021-03-10`), **and have not run any release in between**. Everyone else can ignore this release.
Nimbus `v1.4.0` users might have noticed that they are missing a small number of (seemingly random) attestations since the update. Our investigation into the matter has showed that, due to `v1.4.0`'s significant performance improvements, Nimbus validators occasionally send their first attestation for a new epoch before some peers are ready. These "slow" peers end up dropping early attestations because they're busy with the epoch transition.
It's a rare occurrence, since it requires a validator to be scheduled to attest in the first slot of an epoch *and* for the beacon node to only be connected to "slow" peers for the respective libp2p topic. If both these conditions are true, a premature attestation may be lost in time, like tears in the rain.
As a fix, we are using a larger send delay: [#2705](https://github.com/status-im/nimbus-eth2/pull/2705).
Fo those Nimbus `v1.4.0` users who are concerned about reaching optimal attestation effectiveness, we encourage you to upgrade as soon as possible.
Other changes include log flushing and metrics fixes.
Full list:
- increase attestation wait time ([#2705](https://github.com/status-im/nimbus-eth2/pull/2705))
- ensure logs are printed without delays ([#2669](https://github.com/status-im/nimbus-eth2/pull/2669))
- fix metrics on Windows ([#2707](https://github.com/status-im/nimbus-eth2/pull/2707))
This release is marked as low-urgency - please update at your convenience.
It contains **improvements to attestation effectiveness and CPU usage**.
It also contains **improvements to the RPC APIs**, as suggested by DappNode and RocketPool, and in preparation for our refactored validator client.
### Outdated Nimbus instances
A reminder that if you're running Nimbus with a version prior to `1.0.10` (March 2021) you are exposed to a vulnerability in our core cryptography library (this library is used by all eth2 clients). See this [blst security advisory](https://github.com/supranational/blst/security/advisories/GHSA-x279-68rr-jp4p) for more information. If this concerns you, please update as soon as you can.
## Notable changes
### We've added:
* Nightly builds for the very adventurous. (https://github.com/status-im/nimbus-eth2/pull/2640)
* We expect users of nightly builds to be comfortable providing debugging logs.
### We've fixed:
* RPC API endpoints (https://github.com/status-im/nimbus-eth2/pull/2585, https://github.com/status-im/nimbus-eth2/pull/2586)
*`/eth/v1/beacon/pool/attestations`
*`/api/eth/v1/validator/aggregate_and_proofs`
* Doppelganger detection: fixed false positive on fast restart (https://github.com/status-im/nimbus-eth2/pull/2656/)
### We've improved
* Database read performance improvements during epoch transitions and startup (https://github.com/status-im/nimbus-eth2/pull/2639, https://github.com/status-im/nimbus-eth2/pull/2617)
* Better usage of caches, specially when validating attestations (https://github.com/status-im/nimbus-eth2/pull/2631)
