Skip to main content

Blockchain Release: Snapshot Loading and Storage Improvements

· 4 min read
Abhay Kumar
Rahul Garg
Jeremy Cooper

The core developers have tagged a new 2021.12.29.2 Hotspot firmware release which includes recommended improvements in blockchain-core specifically in how Snapshots are loaded and blocks are stored locally on Hotspot disks.

Snapshot Loading​

As the chain continues to grow in size and more Hotspots come online, Snapshots are starting to become larger than 300 megabytes which make it difficult for some Hotspots to load them entirely into memory. This change to Snapshot loading allows these files to be streamed from disk in pieces and reduce the overall memory requirements for bootstrapping a node. This is important as some Hotspots will reset their local storage and restart syncing blocks from a Snapshot in order to clear room for future blocks.

As a reminder, Snapshots are still generated on-chain by Validators when they come to agreement. The last chain blessed snapshot was created at block height 1156321 or around 2021-12-28 04:07:07 UTC.

Blockchain Garbage Collection​

The longer a Hotspot remains online and follows the blockchain the more storage space it will consume. Most of this storage space is dedicated to storing blocks from the blockchain, but since blocks are less useful the older they are, a long-running Hotspot will eventually run out of space storing blocks that it doesn't need. Previously, manufacturers have exclusively handled out-of-space situations by completely removing the Hotspot's blockchain database and rebuilding it anew by downloading a recent Snapshot and re-syncing. During the sync process, however, the Hotspot is unavailable to participate in Proof-of-Coverage challenges or to route device data -- the very things that make a Hotspot valuable to the network.

To help reduce the frequency and duration of these blockchain database rebuilds and re-syncs, there are two configurable items in the miner process which will enable garbage collection of old blocks at miner startup. These variables are:

  • a BLOCKCHAIN_ROCKSDB_GC_BYTES environment variable (not set by default), and
  • a blocks_to_protect_from_gc variable in the blockchain section of sys.config (current default: 10_000)

At startup, the miner will check for the presence of BLOCKCHAIN_ROCKSDB_GC_BYTES. If it is present, its value will be parsed as an integer and the miner will examine its blockchain database and attempt to prune this many bytes of unneeded blocks from the database. However, the garbage collection process will always keep the most recent blocks_to_protect_from_gc blocks in storage, even if the BLOCKCHAIN_ROCKSDB_GC_BYTES limit hasn't yet been reached, to ensure the Hotspot retains enough recent blocks to function properly.

This should reduce the number of times a Hotspot will need to do a full reset from a Snapshot, reducing the time a Hotspot will be unable to perform Data Transfer or Proof of Coverage.

Additional Updates​

  • The core developers have also modified transfer_hotspot_v2 transaction support to ensure that the owner of the hotspot is the fee payer for the transaction and guarded this change behind transaction_validity_version chain variable. Future updates will be posted to outline the time for activation.

  • This release also contains POC-V11 related performance improvements to prepare for updating the LoraWAN parameters in the near future.

  • Finally, the core developers have also fixed a few long standing sync stall bugs that potentially prevented nodes syncing from the genesis block with full validation.

Plan​

We have been beta testing 2021.12.29.2 since December 29, 2021 05:30 PM PT. Current ETA for GA is 04:30 PM PT, December 30, 2021.