Logging日志记录

Log Location日志位置

You can specify whether the driver logs to stderr or stdout by setting the MONGODB_LOG_PATH environment variable to "stderr" or "stdout", as shown in the following example:您可以通过将MONGODB_LOG_PATH环境变量设置为"stderr"或"stdout"来指定驱动程序是登录到stderr还是stdout，如下例所示：

export MONGODB_LOG_PATH="stderr"

By default, the driver logs to stderr.默认情况下，驱动程序会登录到stderr。

Document Length文件长度

The driver stringifies logged documents by using EJSON, which limits strings to 1000 characters by default. You can specify a maximum document length for your logger by specifying the MONGODB_LOG_MAX_DOCUMENT environment variable. Set this variable to 0 to not perform truncation.驱动程序使用EJSON对记录的文档进行字符串化，默认情况下字符串限制为1000个字符。您可以通过指定MONGODB_LOG_MAX_DOCUMENT环境变量来指定记录器的最大文档长度。将此变量设置为0以不执行截断。

The following example sets the maximum document length to 500 characters:以下示例将最大文档长度设置为500个字符：

export MONGODB_LOG_MAX_DOCUMENT_LENGTH=500

Log Location日志位置

You can specify whether the driver logs to stderr or stdout by setting the mongodbLogPath option to "stderr" or "stdout", as shown in the following example:您可以通过将mongodbLogPath选项设置为"stderr"或"stdout"来指定驱动程序是登录到stderr还是stdout，如下例所示：

const mongodbLogComponentSeverities = {
    default: "debug"
};

const mongodbLogPath = "stdout";
const client = new MongoClient("<connection string>",
    { mongodbLogComponentSeverities, mongodbLogPath }
);

By default, the driver logs to stderr.默认情况下，驱动程序会登录到stderr。

You can also specify a custom log destination. The following example creates a custom log destination:您还可以指定自定义日志目标。以下示例创建自定义日志目标：

import fs from 'node:fs/promises';
import util from 'node:util';

const mongodbLogPath = {
    file: await fs.open(`./server-${+new Date()}.logs`, 'w'),
    async write(log) {
        try {
            await this.file?.appendFile(util.inspect(log) + '\n');
        } catch (fileError) {
            console.log('cannot log anymore', fileError);
            this.file = null;
        }
    }
}

const client = new MongoClient("<connection string>", { mongodbLogPath });

If your function throws an error in the write operation, the thrown error ends the logger. Because of this, we recommend that you handle errors by making the write function a no-op rather than throwing an error, as shown in the preceding example.如果你的函数在写操作中抛出错误，抛出的错误将结束记录器。因此，我们建议您通过将write函数设置为no操作来处理错误，而不是抛出错误，如上例所示。

Document Length文件长度

The driver stringifies logged documents by using EJSON, which limits strings to 1000 characters by default. You can specify a maximum document length for your logger by specifying the mongodbLogMaxDocumentLength option. Set this option to 0 to perform no truncation.驱动程序使用EJSON对记录的文档进行字符串化，默认情况下字符串限制为1000个字符。您可以通过指定mongodbLogMaxDocumentLength选项来指定记录器的最大文档长度。将此选项设置为0以不执行截断。

The following example sets the maximum document length to 500 characters:以下示例将最大文档长度设置为500个字符：

const mongodbLogComponentSeverities = {
    default: "debug"
};

const mongodbLogLength = 500;
const client = new MongoClient("<connection string>", {
    mongodbLogComponentSeverities,
    mongodbLogLength
});