Chainweb

This version replaces all previous versions. Any prior version will stop working
on **2020-11-19T00:00:00Z**. Node administrators must upgrade to this version
before that date.

This version will stop working on **2021-01-14T00:00:00Z**.

* Support for Pact Events (1157)
* **Upgrade to Pact 3.7.** This includes an API change to the `pact` endpoints for events. For further information see the [Pact readthedocs](https://pact-language.readthedocs.io/en/latest/pact-reference.html#events-1). (1157,1158)

This version replaces all previous versions. Any prior version will stop working
on **2020-10-15T00:00:00Z**. Node administrators must upgrade to this version
before that date.

This version will stop working on **2020-11-19T00:00:00Z**.

* Upgrade to Rosetta version 1.4.4 (1149)

* Adjust the default API request rate limits to better match the expected
networking loads for 20 chains. This reduces overhead due to HTTP responses
with status 429 and improves catchup performance. (1152)

This release provides performance improvements and bug fixes.

* More rigorously check the correct length of request keys,
transactions ids, and hashes in API requests. (1139, 1140)

* Fix a bug in the Mempool where transactions that have been included in a
block are still marked as pending. Those transactions occupied memory in the
Mempool and got synchronized between nodes until they finally expired.
(1138)

* The database pruning at node startup is more efficient and can now
operate in four different modes, which can be used on the command line with
the `--prune-chain-database` option and in the configuration file with the
property `chainweb.cuts.pruneChainDatabase`.

* `none` no database pruning is performed
* `headers` only block headers but no payloads are pruned (10-30 seconds)
* `headers-checked` like `headers` but also validates all block headers and
checks the complete chain Merkle tree including payload hashes.
(5-20 minutes)
* `full` prunes block headers and payloads. (10-20 minutes)

The default is `headers`. For backward compatibility it is possible to also
use Boolean values for setting `chainweb.cuts.prunChainDatabase` in the
configuration file, where `false` is equivalent with `none` and `true` is
equivalent with `headers`. (1132)

* Improved performance of rebuilding the pact database from the
chain data. (1137)

This version replaces all previous versions. Any prior version will stop working
on **2020-08-13T00:00:00Z**. Node administrators must upgrade to this version
before that date.

This version will stop working on **2020-10-15T00:00:00Z**.

*Forks:*

This version includes the fork that adds 10 additional chains to Chainweb
resulting in 20 chains in total. The fork will occur on

* Mainnet at block height 852,054, which is expected to happen around
2020-08-20 16:55:14 UTC.

The mining API of chainweb-node will start serving work items for the new chains
starting at above block heights for the respective network. The mempool and pact
service APIs will accept requests already some time before the transition. POW
difficulties will re-adjust within a few hours after the transition. During that
time block rates may be slightly higher or lower than usual.

*Possibly Breaking Changes:*

* Fix the database location and layout when a custom location is configured.
(1128)

This only affects users who configured custom database locations.

This is a potentially breaking change. The chainweb node tries hard to
adjust the database location by itself without user intervention. If you
have tooling that depends on a custom database location, you may want check
the logs at first start up and double check that everything works as expected.

* Deprecate the use of the node-id configuration. (1128)

This only affects users who configured the node-id either on the command line or
in the configuration files.

Any node-id settings are now ignored. In particular the database locations
doesn't include the node-id any more and just defaults to `0/rocksDb` and
`0/sqlitedb`.

*Other Changes*:

* Fix a bug where Chainweb node would fail to start when it stopped after
the last block that pact evaluated got orphaned. (1123)
* Improve failure response for invalid solved work. (1126)
* Fix mainnet coin v2 upgrade for new chains. (1130)

This version replaces all previous versions. Any prior version will stop working
on **2020-07-16T00:00:00Z**. Node administrators must upgrade to this version
before that date.

This version will stop working on **2020-08-13T00:00:00Z**.

This version includes the fork that adds 10 additional chains to Chainweb
resulting in 20 chains in total. The fork will occur on

* Testnet at block height 332,604, which is expect to happen around
2020-07-28 16:00:00 UTC, and
* Mainnet at block height 852,054, which is expected to happen around
2020-08-20 16:00:00 UTC.

The mining API of chainweb-node will start serving work items for the new chains
starting at above block heights for the respective network. The mempool and pact
service APIs will accept requests already some time before the transition. POW
difficulties will re-adjust within a few hours after the transition. During that
time block rates may be slightly higher or lower than usual. Node operators and
miners are encouraged to participate in the transition of Testnet as a dress
rehearsal for the mainnet transition.

Other changes:

* Full support for [Rosetta](https://www.rosetta-api.org).
(1050, 1077, 1079, 1093)
* Support for Pact continuations in `local` queries. (1080)
* Make Pact service more stable and fix a memory leak. (1104, 1100)
* Fix a Pact bug related to module namespaces. (1107)
* Make `info` endpoint show currently in use chains. (1099)
* An improved difficulty adjustment algorithm to support the graph transition
and improve overall performance. Some research background regarding the new
algorithm can be found [in this document](https://github.com/larskuhtz/ChainwebSimulations/blob/master/Results.ipynb).
(1075)

Beside these major changes, the release includes several smaller bug fixes and
performance improvements.

This version replaces all previous versions. Any prior version will stop working
on **2020-06-11T00:00:00Z**. Node administrators must upgrade to this version
before that date.

This version will stop working on **2020-07-16T00:00:00Z**.

This release doesn't introduce new features. It contains many small bug fixes,
along with some performance and stability improvements. It also introduces some
larger behind the scenes changes in preparation of upcoming major new
functionality. User-facing bug fixes and improvements are listed below.
* Improve reliability of `local` API calls by using cached header data instead of a potentially failing lookup causing spurious `TreeDbKeyNotFoundException` failures (1062)
* Provide clean shutdown via SIGTERM (1052)