import pino from "pino"
import { LOG_LEVEL, LOG_FILE } from "../config/env.js"
import fs from "fs"
import path from "path"
/**
* MCP server logging configuration
*
* Note: MCP protocol uses stdout for communication, so all logs are output to stderr.
* To prevent clients from treating normal logs as errors, we adopt the following strategy:
* 1. stderr only outputs warn/error/fatal level logs (to avoid being marked as error)
* 2. info/debug/trace level logs only output to file (if LOG_FILE is set)
* 3. If LOG_FILE is not set, info level logs are not output at all (to avoid confusion)
* 4. Use silent mode to completely disable logging (when LOG_LEVEL=silent)
* 5. Use PRETTY_LOG=true to enable formatted output (even when LOG_FILE is set)
*/
const logLevel =
LOG_LEVEL || (process.env.NODE_ENV === "development" ? "info" : "warn")
// Check if pretty log is enabled
const prettyLog =
process.env.PRETTY_LOG === "true" || process.env.PRETTY_LOG === "1"
// stderr log level: only output warn/error/fatal, avoid info being marked as error
const stderrLogLevel = "warn"
// Create logger instance
const loggerOptions: pino.LoggerOptions = {
level: logLevel,
}
// Create logger
let logger: pino.Logger
// Pretty print options
// Note: customPrettifiers cannot be used with pino.transport (worker thread limitation)
// Error formatting is handled in errorFormatter.ts instead
const prettyOptions = {
colorize: true,
translateTime: "SYS:standard",
ignore: "pid,hostname",
singleLine: false,
hideObject: false,
errorLikeObjectKeys: ["err", "error"],
messageFormat: "{msg}",
}
// If LOG_FILE is set, use multistream to output to stderr and file separately
if (LOG_FILE) {
const logFilePath = path.isAbsolute(LOG_FILE)
? LOG_FILE
: path.resolve(process.cwd(), LOG_FILE)
// Ensure log file directory exists
const logDir = path.dirname(logFilePath)
if (!fs.existsSync(logDir)) {
fs.mkdirSync(logDir, { recursive: true })
}
// Create output stream array
const streams: Array<{ level: string; stream: pino.DestinationStream }> = []
// stderr output: only output warn/error/fatal (to avoid info being marked as error)
if (prettyLog || process.env.NODE_ENV === "development") {
// Use pretty format for stderr
streams.push({
level: stderrLogLevel,
stream: pino.transport({
target: "pino-pretty",
options: {
...prettyOptions,
destination: 2, // stderr
},
}) as unknown as pino.DestinationStream, // Cast to compatible type
})
} else {
streams.push({
level: stderrLogLevel,
stream: pino.destination(2),
})
}
// File output: output all level logs
if (prettyLog) {
// Use pretty format for file too (if PRETTY_LOG is enabled)
streams.push({
level: logLevel,
stream: pino.transport({
target: "pino-pretty",
options: {
...prettyOptions,
destination: fs.createWriteStream(logFilePath, {
flags: "a",
}),
},
}) as unknown as pino.DestinationStream, // Cast to compatible type
})
} else {
// Raw JSON format (convenient for parsing and searching)
streams.push({
level: logLevel,
stream: fs.createWriteStream(logFilePath, { flags: "a" }),
})
}
// Use multistream to output to multiple targets simultaneously
logger = pino(loggerOptions, pino.multistream(streams))
} else {
// LOG_FILE not set, only output warn/error/fatal to stderr
// info/debug/trace level logs are not output (to avoid being marked as error)
loggerOptions.level = stderrLogLevel
// Use pino-pretty for formatted output in development or when PRETTY_LOG is enabled
if (prettyLog || process.env.NODE_ENV === "development") {
loggerOptions.transport = {
target: "pino-pretty",
options: prettyOptions,
}
}
// Output to stderr (MCP protocol requires stdout for protocol communication)
logger = pino(loggerOptions, pino.destination(2))
}
export { logger }
