WAX Technical How To #19

Published in

EOSphere Blog

4 min readAug 16, 2023

Whether it’s restarting an ungracefully shutdown node, spinning up a lite node or using the tmpfs memory strategy for better performance, nodeos snapshots are needed to return the chain state database to a valid point in time so the node may rejoin and sync with the network.

The chain state database shared_memory.binis needed by nodeosto run, it is a memory mapped file that contains the state associated with each block, including smart contract data, account details and deferred transactions.

If you are familiar with the WAX Guild ecosystem, you will know that there are numerous providers of reliable snapshots. However best practice would be for a top tier Guild to create their own snapshots and potentially share them with the rest of the community.

This guide will share the scripting method that the EOSphere Guild uses to create and manage snapshots. At time of writing Leap v4.0.4 is available with expanded snapshot functionality built into the eosio::producer_api_plugin that may accomplish the same as the EOSphere method, this will be covered in a future guide.

Automate WAX Snapshots

Before creating a snapshot it needs to be mentioned that the node will essentially pause during the process, depending on the the size of the chains state database (currently 90GB on WAX Mainnet) this may take some time.

With this in mind it is recommended that a dedicated not in production server is use for creating snapshots.

Installation, Configuration and Running

In this example the goal is to:

Configure nodeos
Configure snapshot script
Configure delete script
Configure a CronJob

Configure nodeos

A synchronised WAX node with the eosio::producer_api_plugin enabled is used as the snapshot server. Configure as below:

> nano config.ini

plugin = eosio::producer_api_plugin

Snapshots will be saved to the /snapshots folder - ensure there is sufficient disk space available.

Please see How to Setup a Solid WAX Mainnet Node for a guide on WAX node build, config and operation.

Configure snapshot script

This script will accomplish the following on the snapshot node:

Take Snapshot
Label snapshot with current block number
Archive snapshot
Transfer snapshot to repository

Add dependency applications:

> sudo apt update

#jq is a lightweight and flexible command-line JSON processor
> sudo apt install jq

#Zstandard lossless data compression
> sudo apt install zstd

Create the snapshot script as below adjusting to your environment:

> nano snapshot.sh


#!/bin/bash

logs='/home/eosphere/scripts/logs'
now=$(date +"%Y-%d-%m_%H-%M")
logfile="$logs/$now.txt"

echo $logfile
echo "Create snapshot" >> $logfile

result=$(curl -X POST http://127.0.0.1:8888/v1/producer/create_snapshot) >> $logfile

head_block=$(echo "$result" | jq -r '.head_block_id')
snap_name=$(echo "$result" | jq -r '.snapshot_name')

echo $head_block >> $logfile
echo $snap_name >> $logfile

block_num=$(/home/eosphere/wax-leap/build/programs/cleos/cleos -u https://wax.eosphere.io get block "$head_block" | jq '.block_num')

echo $block_num >> $logfile

outfile="/home/eosphere/scripts/snapshot-wax-$block_num-$now.bin.zst"

echo "Create compressed image" >> $logfile

/usr/bin/zstd -z -T1 "$snap_name" -o "$outfile" >> $logfile

echo "Copy to repository" >> $logfile

/usr/bin/rsync -e "ssh -i /home/eosphere/.ssh/mrsnapshot.pem" -a --progress "$outfile" "mrsnapshot@10.0.0.101:/home/mrsnapshot/snapshots/wax/" >> $logfile

echo "Complete" >> $logfile


> chmod +x snapshot.sh

In the above example script:

logs are stored here /home/eosphere/scripts/logs
the cleos binary is located here /home/eosphere/wax-leap/build/programs/cleos/cleos
the compressed and labelled snapshot is stored here /home/eosphere/scripts
the created compressed and labelled snapshot is copied to a repository 10.0.0.101 using an ssh certificate mrsnapshot.pem and a username mrsnapshot

The script is executed as below:

> ./snapshot.sh

Configure delete script

To ensure the snapshot node doesn’t run out of disk space old snapshot’s are deleted with the below script:

> nano delete.sh

#! /bin/bash  
/usr/bin/find /home/eosphere/datavolume1/waxdata1/snapshots -name "*.bin" -type f -mtime +1 -exec rm -f {} \;
/usr/bin/find /home/eosphere/scripts -name "*.zst" -type f -mtime +2 -exec rm -f {} \;

> chmod +x delete.sh

In the above script:

raw nodeos .bin snapshots are deleted after a day (-mtime +1)
compressed and labelled snapshots are deleted after 2 days (-mtime +2)

The script is executed as below:

> ./delete.sh

Configure a CronJob

Running a CronJob is a great way to regularly schedule the snapshot and delete scripts. To run once a day configure as below:

> crontab -e

0 12 * * * /home/eosphere/scripts/snapshot.sh
0 16 * * * /home/eosphere/scripts/delete.sh

In the above CronJob:

snapshot.sh is run once a day at 12h00
delete.sh is run once a day at 16h00

The collection of compressed and labelled snapshots can then be shared with the community from the repository using a basic html webpage such as EOSphere Snapshot and Backups

Be sure to ask any questions in the EOSphere Telegram

EOSphere Guild is a Block Producer on the WAX Protocol Network as well as many other Antelope based Blockchains.

If you find our work helpful, please vote for us on the WAX Mainnet: eosphereiobp

If you prefer to proxy your vote, our proxy account is : blklotusprxy

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