Writing to the function execution log

If you do not have the Yandex Cloud command line interface yet, install and initialize it.

The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

Logging destinationLogging destination

If a custom log group is not specified in the function version parameters or logging is not turned off, the function automatically writes all logs to the default log group for the folder it resides in.

To write logs to a custom log group, provide the log group ID in the --log-group-id parameter when creating a function version. The log group must reside in the same folder as the function.

Minimum logging levelMinimum logging level

To set a minimum logging level, provide it in the --min-log-level parameter when creating a function version.

If you set the minimum logging level, logs of that level and higher will be written to the execution log. With no minimum logging level set, all function logs will be written to the execution log.

Disabling loggingDisabling logging

To disable logging, set the --no-logging parameter when creating a function version.

Command exampleCommand example

To write logs to a custom log group, run this command:

yc serverless function version create \
  --function-id <function_ID> \
  --runtime <runtime_environment> \
  --entrypoint <entry_point> \
  --memory <RAM_size> \
  --source-path <ZIP_archive_with_function_code> \
  --log-group-id <log_group_ID> \
  --min-log-level <minimum_logging_level>

Where:

• --function-id: Function ID.
• --runtime: Runtime environment.
• --entrypoint: Entry point in the following format: <file_name_without_extension>.<listener_name>.
• --memory: Amount of RAM.
• --source-path: ZIP archive with the function code and required dependencies.
• --log-group-id: ID of the log group to write logs to.
• --min-log-level: Minimum logging level. This is an optional parameter.

Result:

done (4s)
id: d4ech7qdki6r********
function_id: d4e7tbg7m4np********
created_at: "2024-04-19T10:13:00.019Z"
runtime: python37
entrypoint: index.handler
resources:
  memory: "134217728"
execution_timeout: 5s
image_size: "53248"
status: ACTIVE
tags:
  - $latest
log_options:
  log_group_id: e23u2vn449av********
  min_level: DEBUG

Terraform allows you to quickly create a cloud infrastructure in Yandex Cloud and manage it using configuration files. Configuration files store the infrastructure description in the HashiCorp Configuration Language (HCL). Terraform and its providers are distributed under the Business Source License.

For more information about the provider resources, see the documentation on the Terraform website or the mirror.

If you change the configuration files, Terraform automatically detects which part of your configuration is already deployed, and what should be added or removed.

If you don't have Terraform, install it and configure the Yandex Cloud provider.

Logging destinationLogging destination

If a custom log group is not specified in the function version parameters or logging is not turned off, the function automatically writes all logs to the default log group for the folder it resides in.

To write logs to a custom log group, provide the log group ID in the log_group_id parameter under log_options when creating a function version. The log group must reside in the same folder as the function.

Minimum logging levelMinimum logging level

To set a minimum logging level, provide it in the log_group_id parameter when creating a function version.

If you set the minimum logging level, logs of that level and higher will be written to the execution log. With no minimum logging level set, all function logs will be written to the execution log.

Disabling loggingDisabling logging

To disable logging, set the disabled parameter to true under log_options when creating a function version.

ExampleExample

To write logs to a custom log group:

1. Open the Terraform configuration file and add the log_options section to the yandex_function resource description:

   Here are some examples of the configuration file structure:

   resource "yandex_function" "<function_name>" {
     name       = "<function_name>"
     user_hash  = "<any_string>"
     runtime    = "<runtime_environment>"
     entrypoint = "<entry_point>"
     memory     = "<RAM_size>"
     content {
       zip_filename = "<ZIP_archive_name>"
     }
     log_options {
       log_group_id = "<log_group_ID>"
       min_level = "<minimum_logging_level>"
     }
   }
   

   Where:

   • name: Function name.
   • user_hash: Any string to identify the function version.
   • runtime: Function runtime environment.
   • entrypoint: Function name in the source code that will serve as an entry point to applications.
   • memory: Amount of memory allocated for the function, in MB.
   • content: Function source code.
     • zip_filename: Name of the ZIP archive containing the function source code.
   • log_group_id: ID of the log group to write logs to.
   • min_level: Minimum logging level. This is an optional parameter.

   For more information about the yandex_function resource parameters, see the provider documentation.

2. Check the configuration using this command:

   terraform validate
   

   If the configuration is correct, you will get this message:

   Success! The configuration is valid.
   

3. Run this command:

   terraform plan
   

   The terminal will display a list of resources with parameters. No changes will be made at this step. If the configuration contains any errors, Terraform will point them out.

4. Apply the configuration changes:

   terraform apply
   

5. Confirm the changes: type yes into the terminal and press Enter.

To write to the function execution log, use the createVersion REST API method for the Function resource or the FunctionService/LogOptions gRPC API call.

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")

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)

def handler(event, context):
    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!";
    }
}