@subsquid/logger

Lightweight structured logger for squid framework.

Usage

import {createLogger} from "@subsquid/logger"

const log = createLogger('sqd:demo')

log.info('message with severity info')
log.debug('message with severity debug')

log.info({foo: 1, bar: 2}, 'message and some additional attributes')

// info message consisting only of attributes
log.info({a: 1, b: 2, c: 3, array: [4, 5], obj: {foo: 'foo', bar: "bar"}}) 

// pass an Error object inplace of attributes
log.warn(new Error('Some error occured'))

// Error together with some other attributes and message
log.error({err: new Error('Another error'), a: 1, b: 2}, 'weird')

// create a child logger instance with namespace `sqd:demo:sql` 
// and `req: 1` attribute attached to every log record
const sqlLog = log.child('sql', {req: 1})
sqlLog.debug('connecting to database')
sqlLog.debug({sql: 'SELECT max(id) FROM status'})

Configuration

There are 6 log levels available: TRACE, DEBUG, INFO, WARN, ERROR, FATAL.

The log level of each logger instance is solely determined by its namespace and specified via set of SQD_TRACE, ..., SQD_FATAL environment variables. The default log level is INFO.

Users override the default log level by setting in appropriate environment variable a pattern which matches the logger's namespace.

• SQD_DEBUG=* - sets the log level to DEBUG for all loggers.
• SQD_DEBUG=foo - loggers foo, foo:bar, foo🅰️b, etc will have a DEBUG level.
• SQD_DEBUG=a:b*:c,d - loggers a🅱️c, a:baz:c, a:baz:c:foo, d, etc will have a DEBUG level, logger a:z:c will not.

When logger is matched by multiple SQD_* variables, the match with the highest specificity wins. When specificities are equal, the most verbose matched log level will be effective.

Specificity is computed as a number of namespace characters which are not matched by wildcards and which are not part of a child namespace. For example, given a pattern foo*bar, the specificity of foo:bar:baz:qux, foobar and foobazbar is 6.

Output

The logger always writes to stderr.

When stderr is connected to a terminal, log records will be pretty printed.

Otherwise, log records will be written as JSON lines.

{"level":2,"time":1669387525765,"ns":"sqd:demo","msg":"message with severity info"}
{"level":2,"time":1669387525766,"ns":"sqd:demo","msg":"message and some additional attributes","foo":1,"bar":2}
{"level":2,"time":1669387525766,"ns":"sqd:demo","a":1,"b":2,"c":3,"array":[4,5,6],"obj":{"foo":"foo","bar":"bar"}}
{"level":3,"time":1669387525766,"ns":"sqd:demo","err":{"stack":"Error: Some error occured\n    at Object.<anonymous> (/Users/eldar/dev/squid/util/logger/lib/demo.js:11:10)\n    at Module._compile (node:internal/modules/cjs/loader:1159:14)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1213:10)\n    at Module.load (node:internal/modules/cjs/loader:1037:32)\n    at Module._load (node:internal/modules/cjs/loader:878:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at node:internal/main/run_main_module:23:47"}}
{"level":4,"time":1669387525766,"ns":"sqd:demo","msg":"weird","err":{"stack":"Error: Another error\n    at Object.<anonymous> (/Users/eldar/dev/squid/util/logger/lib/demo.js:13:18)\n    at Module._compile (node:internal/modules/cjs/loader:1159:14)\n    at Module._extensions..js (node:internal/modules/cjs/loader:1213:10)\n    at Module.load (node:internal/modules/cjs/loader:1037:32)\n    at Module._load (node:internal/modules/cjs/loader:878:12)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n    at node:internal/main/run_main_module:23:47"},"a":1,"b":2}