Redis based block follower is an efficient way for multiple apps to stream the Steem Blockchain.
If you have multiple applications that need to perform actions as operations occur, meeseeker will allow your apps to each perform actions for specific operations without each app having to stream the entire blockchain.
In a nutshell: The overarching intent here is to provide a "live view" of the blockchain, not store the entire blockchain. Apps can attach to your redis source and ask, "What just happened?"
Repository:
https://github.com/inertia186/meeseeker
Purpose
Although Meeseeker tracks all operations, it is only intended to provide other applications signals that those operations have happened. It is not intended to provide cryptographically verifiable events.
Possible uses:
- Notifications of events, suitable for push to mobile devices or web browsers.
- Invoke periodic updates on a threshold.
- Light-weight bots that only care about a limit set of operations, reducing the number of API calls.
Why Redis?
Redis is a persistent key-value database, with built-in net interface. See: https://redis.io/
It allows for quick storage and lookup of operations by key as well as the ability to automatically expire keys that are no longer needed.
Installation
First, install redis:
On linux:
sudo apt install redis-server
On macOS:
brew install redis
Next, install ruby. One way to do this is install rvm. Once ruby is installed, install meeseeker with the gem command:
gem install meeseeker
This installs meeseeker as a command available to the OS, e.g.:
meeseeker help
To do the actual sync to your local redis source (defaults assume redis://127.0.0.1:6379/0):
meeseeker sync
To specify an alternative redis source:
MEESEEKER_REDIS_URL=redis://:[email protected]:6380/15 meeseeker sync
You can also specify an alternative Steem node:
MEESEEKER_NODE_URL=https://api.steemit.com meeseeker sync
To sync from the head block instead of the last irreversible block:
MEESEEKER_STREAM_MODE=head meeseeker sync
To ignore virtual operations (useful if the node doesn't enable get_ops_in_blocks or if you want to sync from the head block):
MEESEEKER_INCLUDE_VIRTUAL=false meeseeker sync
Normally, keys stay on redis for 24 hours. If you want to change this behavior, use MEESEEKER_EXPIRE_KEYS and specify the new value in seconds, for example:
MEESEEKER_EXPIRE_KEYS=10 meeseeker sync
Usage
When meeseeker sync starts for the first time, it initializes from the last irreversible block number. If the sync is interrupted, it will resume from the last block sync'd unless that block is older than MEESEEKER_EXPIRE_KEYS in which case it will skip to the last irreversible block number.
Using SUBSCRIBE
For redis-cli, please see: https://redis.io/topics/pubsub
Channels available for meeseeker:
steem:blocksteem:transactionsteem:op:votesteem:op:commentsteem:op:whatever(replace "whatever" with the op you want)
As mentioned in the last whatever example, all operation types can be subscribed to as channels, including virtual operations, if enabled.
For example, from redis-cli, if we wanted to stream block numbers:
$ redis-cli
127.0.0.1:6379> subscribe steem:block
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "steem:block"
3) (integer) 1
1) "message"
2) "steem:block"
3) "{\"block_num\":29844374}"
1) "message"
2) "steem:block"
3) "{\"block_num\":29844375}"
1) "message"
2) "steem:block"
3) "{\"block_num\":29844376}"
A ruby application can subscribe to a channel as well, using the redis gem:
require 'redis'
url = 'redis://127.0.0.1:6379/0'
ctx = Redis.new(url: url)
Redis.new(url: url).subscribe('steem:op:comment') do |on|
on.message do |channel, message|
payload = JSON[message]
comment = JSON[ctx.get(payload['key'])]
puts comment['value']
end
end
Many other clients are supported: https://redis.io/clients
Using SCAN
From the redis manual:
Since these commands allow for incremental iteration, returning only a small number of elements per call, they can be used in production without the downside of commands like KEYS or SMEMBERS that may block the server for a long time (even several seconds) when called against big collections of keys or elements.
However while blocking commands like SMEMBERS are able to provide all the elements that are part of a Set in a given moment, The SCAN family of commands only offer limited guarantees about the returned elements since the collection that we incrementally iterate can change during the iteration process.
See: https://redis.io/commands/scan
Keep in mind that SCAN requires pagination to get a complete result. Redis implements pagination using a cursor based iterator.
See: https://redis.io/commands/scan#scan-basic-usage
Once your sync has started, you can begin doing queries against redis, for example, in the redis-cli:
redis-cli --scan --pattern 'steem:*:vote'
This returns the keys, for example:
steem:29811083:7fd2ea1c73e6cc08ab6e24cf68e67ff19a05896a:0:vote
steem:29811085:091c3df76322ec7f0dc51a6ed526ff9a9f69869e:0:vote
steem:29811085:24bfc199501779b6c2be2370fab1785f58062c5a:0:vote
steem:29811086:36761db678fe89df48d2c5d11a23cdafe57b2476:0:vote
steem:29811085:f904ac2e5e338263b03b640a4d1ff2d5fd01169e:0:vote
steem:29811085:44036fde09f20d91afda8fc2072b383935c0b615:0:vote
steem:29811086:570abf0fbeeeb0bb5c1e26281f0acb1daf175c39:0:vote
steem:29811083:e3ee518c4958a10f0d0c5ed39e3dc736048e8ec7:0:vote
steem:29811083:e06be9ade6758df59e179160b749d1ace3508044:0:vote
To get the actual vote operation for a particular key, use:
redis-cli get steem:29811085:f904ac2e5e338263b03b640a4d1ff2d5fd01169e:0:vote
If, on the other hand, you want custom_json only:
redis-cli --scan --pattern 'steem:*:custom_json'
This only returns the related keys, for example:
steem:29811084:43f1e1a367b97ea4e05fbd3a80a42146d97121a2:0:custom_json
steem:29811085:5795ff73234d64a11c1fb78edcae6f5570409d8e:0:custom_json
steem:29811083:2d6635a093243ef7a779f31a01adafe6db8c53c9:0:custom_json
steem:29811086:31ecb9c85e9eabd7ca2460fdb4f3ce4a7ca6ec32:0:custom_json
steem:29811083:7fbbde120aef339511f5af1a499f62464fbf4118:0:custom_json
steem:29811083:04a6ddc83a63d024b90ca13996101b83519ba8f5:0:custom_json
To get the actual custom json operation for a particular key, use:
redis-cli get steem:29811083:7fbbde120aef339511f5af1a499f62464fbf4118:0:custom_json
To get all transactions for a particular block number:
redis-cli --scan --pattern 'steem:29811085:*'
Or to get all ops for a particular transaction:
redis-cli --scan --pattern 'steem:*:31ecb9c85e9eabd7ca2460fdb4f3ce4a7ca6ec32:*'
See some of my previous Ruby How To posts in: #radiator #ruby
Get in touch!
If you're using Radiator, I'd love to hear from you. Drop me a line and tell me what you think! I'm @inertia on STEEM.
License
I don't believe in intellectual "property". If you do, consider Radiator as licensed under a Creative Commons 
License.