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Yandex Cloud Functions

Logging data to the function execution log

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Apart from text, you can write structured logs to the standard output stream (stdout) and standard error output stream (stderr).

Function examples

requirements.txt

python-json-logger==2.0.4

index.py

import logging
from pythonjsonlogger import jsonlogger


class YcLoggingFormatter(jsonlogger.JsonFormatter):
    def add_fields(self, log_record, record, message_dict):
        super(YcLoggingFormatter, self).add_fields(log_record, record, message_dict)
        log_record['logger'] = record.name
        log_record['level'] = str.replace(str.replace(record.levelname, "WARNING", "WARN"), "CRITICAL", "FATAL")


def handler(event, context):
    logHandler = logging.StreamHandler()
    logHandler.setFormatter(YcLoggingFormatter('%(message)s %(level)s %(logger)s'))

    logger = logging.getLogger('MyLogger')
    logger.propagate = False
    logger.addHandler(logHandler)
    logger.setLevel(logging.DEBUG)

    logger.info("My log message", extra={"my-key": "my-value"})

    return "Hello, world!"

index.go

package main

import (
    "context"
    "go.uber.org/zap"
)

type Response struct {
    StatusCode int         `json:"statusCode"`
    Body       interface{} `json:"body"`
}

func Handler(ctx context.Context) (*Response, error) {
    config := zap.NewProductionConfig()
    config.DisableCaller = true
    config.Level.SetLevel(zap.DebugLevel)
    logger, _ := config.Build()
    defer logger.Sync()

    logger.Info(
        "My log message",
        zap.String("my-key", "my-value"),
    )

    return &Response{
        StatusCode: 200,
        Body:       "Hello, world!",
    }, nil
}

pom.xml

...
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.19.0</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.19.0</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-layout-template-json</artifactId>
    <version>2.19.0</version>
</dependency>
...

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <JsonTemplateLayout eventTemplateUri="classpath:YcLoggingLayout.json"/>
        </Console>
    </Appenders>
    <Loggers>
        <Root level="TRACE">
            <AppenderRef ref="Console"/>
        </Root>
    </Loggers>
</Configuration>

YcLoggingLayout.json

{
  "message": {
    "$resolver": "message",
    "stringified": true
  },
  "level": {
    "$resolver": "level",
    "field": "name"
  },
  "logger": {
    "$resolver": "logger",
    "field": "name"
  },
  "labels": {
    "$resolver": "mdc",
    "flatten": true,
    "stringified": true
  },
  "tags": {
    "$resolver": "ndc"
  }
}

Handler.java

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.ThreadContext;

import java.util.function.Function;

public class Handler implements Function<String, String> {

    private static final Logger logger = LogManager.getLogger();

    @Override
    public String apply(String s) {
        ThreadContext.put("my-key", "my-value");
        logger.info("My log message");
        ThreadContext.clearAll();
        return "Hello, world!";
    }
}