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Jan 4, 2022
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docs(logger): improve mkdocs and examples of sample rate feature #389

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98 changes: 83 additions & 15 deletions docs/core/logger.md
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Original file line number Diff line number Diff line change
Expand Up @@ -456,63 +456,131 @@ For example, by setting the "sample rate" to `0.5`, roughly 50% of your lambda i

=== "handler.ts"

```typescript hl_lines="5"
```typescript hl_lines="6"
import { Logger } from "@aws-lambda-powertools/logger";

// Notice the log level set to 'ERROR'
const logger = new Logger({
logLevel: "ERROR",
sampleRateValue: 0.5
});

const lambdaHandler = async () => {

// 0.5 means that you have 50% chance that these logs will be printed
logger.info("This is INFO log #1");
logger.info("This is INFO log #2");
logger.info("This is INFO log #3");
logger.info("This is INFO log #4");

// This log item (equal to log level 'ERROR') will be printed to standard output
// in all Lambda invocations
logger.error("This is an ERROR log");

// These log items (below the log level 'ERROR') have ~50% chance
// of being printed in a Lambda invocation
logger.debug("This is a DEBUG log that has 50% chance of being printed");
logger.info("This is an INFO log that has 50% chance of being printed");
logger.warn("This is a WARN log that has 50% chance of being printed");

// Optional: refresh sample rate calculation on runtime
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Just for my benefit, not trying to be annoying but only to understand myself.

Would this command reset the sample rate count, meaning that from here below all logs would have the original chance (set by sampleRateValue)? What's an example in which I'd use this?

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@saragerion saragerion Jan 4, 2022 •
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meaning that from here below all logs would have the original chance (set by sampleRateValue)?

Almost! Not "from here below", but for all logs produced by that logger instance

What's an example in which I'd use this?

If I remember correctly this was a feature request by the community for the python tool, I need to find the conversation

// logger.refreshSampleRateCalculation();

};
```

=== "Example CloudWatch Logs excerpt"
=== "Example CloudWatch Logs excerpt - Invocation #1"

```json hl_lines="4 12 20 28"
```json
{
"level": "INFO",
"message": "This is INFO log #1",
"level": "ERROR",
"message": "This is an ERROR log",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.334Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "INFO",
"message": "This is INFO log #2",
"level": "DEBUG",
"message": "This is a DEBUG log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.337Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "INFO",
"message": "This is INFO log #3",
"message": "This is an INFO log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.338Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "WARN",
"message": "This is a WARN log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.338Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
```

=== "Example CloudWatch Logs excerpt - Invocation #2"

```json
{
"level": "ERROR",
"message": "This is an ERROR log",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.334Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
```

=== "Example CloudWatch Logs excerpt - Invocation #3"

```json
{
"level": "ERROR",
"message": "This is an ERROR log",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.334Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "DEBUG",
"message": "This is a DEBUG log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.337Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "INFO",
"message": "This is INFO log #4",
"message": "This is an INFO log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.338Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
{
"level": "WARN",
"message": "This is a WARN log that has 50% chance of being printed",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.338Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
```

=== "Example CloudWatch Logs excerpt - Invocation #4"

```json
{
"level": "ERROR",
"message": "This is an ERROR log",
"sampling_rate": "0.5",
"service": "shopping-cart-api",
"timestamp": "2021-12-12T22:59:06.334Z",
"xray_trace_id": "abcdef123456abcdef123456abcdef123456"
}
```

### Custom Log formatter (Bring Your Own Formatter)
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19 changes: 12 additions & 7 deletions packages/logger/examples/sample-rate.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
require('./../tests/helpers/populateEnvironmentVariables');

// Additional runtime variables
process.env.LOG_LEVEL = 'WARN';
process.env.LOG_LEVEL = 'ERROR';
process.env.POWERTOOLS_SERVICE_NAME = 'hello-world';
process.env.POWERTOOLS_LOGGER_SAMPLE_RATE = '0.5';

Expand All @@ -15,13 +15,18 @@ const logger = new Logger();

const lambdaHandler: Handler = async () => {

logger.info('This is INFO log #1');
logger.info('This is INFO log #2');
logger.info('This is INFO log #3');
logger.info('This is INFO log #4');
// This log item (equal to log level 'ERROR') will be printed to standard output
// in all Lambda invocations
logger.error('This is an ERROR log');

// Refresh sample rate calculation on runtime
logger.refreshSampleRateCalculation();
// These log items (below the log level 'ERROR') have ~50% chance
// of being printed in a Lambda invocation
logger.debug('This is a DEBUG log that has 50% chance of being printed');
logger.info('This is an INFO log that has 50% chance of being printed');
logger.warn('This is a WARN log that has 50% chance of being printed');

// Optional: refresh sample rate calculation on runtime
// logger.refreshSampleRateCalculation();

return {
foo: 'bar'
Expand Down