hypercore-logger

Distributed logger

npm install hypercore-logger

Usage

const Logger = require('hypercore-logger')

// pass backing hypercore
const log = new Logger(core)

// add a log message
await log.log({ hello: 'world' })

Setup swarming with Hyperswarm on the core and somewhere else

const log = new Logger(core)

for await (const { timestamp, stats, message } of log.tail()) {
  console.log(timestamp, stats, message)
}

API

Logger

const log = new Logger(core)

Create a new logger backed by a Hypercore (core).

log.discoveryKey

The discoverKey of the Hypercore backing the log.

log.key

The key of the Hypercore backing the log.

await log.ready()

Wait for the log to fully open.

await log.log(...msg)

Log the msg arguments as a string representation intended for debugging, like console.log()'s output.

In addition to the string representation, metadata is automatically added to each log. Each appended to the backing Hypercore will look like:

{
  timestamp: Date.now(),
  stats: Stats,
  subsystem: log.subsystem,
  message: '' // String representation of msg
}

Stats includes:

stats: {
  cpus: number, // Number of avaliable cpus
  cpu: number, // Precent of CPU usage
  cpuThread: number, // Percent of thread usage
  cpuDelay: number, // Event loop delay the last ~5s
  rss: integer, // Resident Set Size
  heapUsed: integer, // Amount of heap used in js engine
  heapTotal: integer, // Total size of heap in js engine
  external: integer, // Memory usage of C++ objects bound to JavaScript objects
}

The block is encoded via the Hyperschema schema @logger/entry.

const stream = log.tail(opts)

Returns a live Readable Stream of the contents of the log. Acts like tail -f on a file, showing new data as it's appended.

• start: Index of the starting block
• end: Index of the end block

Example:

for await (const { timestamp, stats, message } of log.tail()) {
  console.log(timestamp, stats, message)
}

await logger.find(opts)

Find start and end blocks to apply filters

• opts.gte: Start at the first entry with a timestamp >= gte

• opts.gt: Start at the first entry with a timestamp > gt

• opts.lte: End before the first entry with timestamp > lte

• opts.lt: End before the first entry with timestamp >= lt

await log.close()

Fully close the log and the Hypercore backing it.

CLI

Comes with a CLI tool for tailing a hypercore-logger.

npm install -g hypercore-logger
hypercore-logger --key <key>

Usage:

hypercore-logger [flags]

Flags:
  --key, -k <key>       log core key
  --peer, -p <key>      noise key of peer
  --storage, -s <dir>   where to store the core, defaults to /tmp/hypercore-logger
  --help|-h             Show help

License

Apache-2.0