# Advanced configuration options for a monitor
This section provides the steps for configuring advanced options for a monitor in Internet Monitor. These configuration options are optional but can be useful in some scenarios.
For example, you might choose to set a city-network maximum limit if traffic for the application that you monitor with Internet Monitor occasionally spikes, and you want to help make sure that your bill for Internet Monitor is predictable.
Or, you might want to set custom or local thresholds for health events, because you want to pay close attention to issues in specific geographies where you have a concentration of clients.
The topics in this section provide detailed descriptions of each feature, and list the steps to configure options for your needs.
**Topics**
+ [Choose a city-networks limit](IMCityNetworksMaximum.md)
+ [Change health event thresholds](CloudWatch-IM-get-started.change-threshold.md)
+ [Publish internet measurements to S3](CloudWatch-IM-get-started.Publish-to-S3.md)
# Choose a city-networks maximum limit
In addition to setting a traffic percentage for your monitor in Internet Monitor, you can also set a maximum limit for the number of city-networks monitored. This section describes how the city-networks limit can help you manage billing costs, and provides information and an example to help you determine a limit to set, if you choose to set one.
Internet Monitor can monitor traffic for some or all of the locations where clients access your AWS application resources. You can set a monitoring limit for the number of *city-networks*, that is, the client locations and the ASNs (typically internet service providers) that clients access your application through.
You choose a [percentage of application traffic](IMTrafficPercentage.md) to monitor when you create your monitor. The default percentage is 100%. You can update the percentage at any time, by editing the monitor.
The maximum limit that you set for the number of city-networks helps to make sure that your bill is predictable. For more information, see [Amazon CloudWatch Pricing](https://aws.amazon.com//cloudwatch/pricing/). You can also learn how different values for the number of city-networks actually monitored can affect your bill by using the CloudWatch price calculator. To explore options, on the [Pricing calculator for CloudWatch page](https://calculator.aws/#/addService/CloudWatch), scroll down to Internet Monitor.
To update your monitor and change the maximum city-networks limit, see [Edit a monitor in Internet Monitor](CloudWatch-IM-get-started.edit-monitor.md).
## How billing works with city-networks maximum limits
Setting a maximum limit for the number of city-networks monitored can help prevent unexpected costs in your bill. This is useful, for example, if your traffic patterns vary widely. Billing costs increase for each city-network that is monitored after the first 100 city-networks, which are included (across all monitors per account). If you set a city-networks maximum limit, it caps the number of city-networks that Internet Monitor monitors for your application, regardless of the percentage of traffic that you choose to monitor.
You only pay for the number of city-networks that are actually monitored. The city-network maximum limit that you choose lets you set a cap on the total that can be included when Internet Monitor monitors traffic with your monitor. You can change the maximum limit at any time by editing your monitor.
To explore options, on the [Pricing calculator for CloudWatch](https://calculator.aws/#/addService/CloudWatch) page, scroll down to Internet Monitor. For more information on Internet Monitor pricing, see the Internet Monitor section on the [Amazon CloudWatch Pricing](https://aws.amazon.com//cloudwatch/pricing/) page.
## How to choose a city-networks maximum limit
Optionally, you can set a city-networks maximum limit. To help you decide on a maximum limit that you might want to select, consider how much traffic you want to monitor for your application. Be aware that if you choose 100% for the *traffic percentage to monitor* for your monitor, and then specify a city-networks maximum limit, depending on the limit that you choose, you might not monitor 100% of your application traffic. The city-networks maximum that you set takes precedence over the traffic percentage to monitor that you set.
To view how the percentage of traffic to monitor that you choose affects the number of city-monitors that are included for your application monitoring, which can help you decide whether to set a city-networks maximum limit, follow the steps in [View the number of city-networks monitored at different traffic percentage settings](IMTrafficPercentage.md#IMExploreTrafficGraphs).
To explore your options in more detail, you can use Internet Monitor metrics, as described in the following examples. These examples show how to select a maximum city-networks limit that is best for you, depending on the breadth of application internet traffic coverage you want. Using the [queries for Internet Monitor metrics in CloudWatch Metrics](CloudWatch-IM-view-cw-tools-metrics-dashboard.md) can help you understand more about your application internet traffic coverage.
## Example of determining a city-networks maximum limit
As an example, say that you've set a monitoring maximum limit of 100 city-networks and that your application is accessed by clients across 2637 city-networks. In CloudWatch Metrics, you'd see the following Internet Monitor metrics returned:
```
CityNetworksMonitored 100
TrafficMonitoredPercent 12.5
CityNetworksFor90PercentTraffic 2143
CityNetworksFor100PercentTraffic 2637
```
From this example, you can see that you're currently monitoring 12.5% of your internet traffic, with the maximum limit set to 100 city-networks. If you want to monitor 90% of your traffic, the next metric provides information about that: `CityNetworksFor90PercentTraffic` indicates that you would need to monitor 2,143 city-networks for 90% coverage. To do that, you would update your monitor and set the maximum city-networks limit to 2,143.
Similarly, say you'd like to have 100% internet traffic monitoring for your application. The next metric, `CityNetworksFor100PercentTraffic`, indicates that to do this, you should update your monitor to set the maximum city-networks limit to 2,637.
If you now set the maximum to 5,000 city-networks, since that's greater than 2,637, you see the following metrics returned:
```
CityNetworksMonitored 2637
TrafficMonitoredPercent 100
CityNetworksFor90PercentTraffic 2143
CityNetworksFor100PercentTraffic 2637
```
From these metrics, you can see that with the higher limit, you monitor all 2,637 city-networks, which is 100% of your internet traffic.
# Change health event thresholds for a monitor
Internet Monitor uses a default threshold to determine when to create a health event for your monitor. Optionally, you can change that default global threshold, to set another value. You can also set local threshold. This section describes how global and local thresholds work together, and provides steps for setting custom thresholds.
You can change the overall threshold that triggers Internet Monitor to create a health event. The default health event threshold, for both performance scores and availability scores, is 95%. That is, when the overall performance or availability score for your application falls to 95% or below, Internet Monitor creates a health event. For the overall threshold, the health event can be triggered by a single large issue, or by the combination of multiple smaller issues.
You can also change the local—that is, city-network—threshold, combined with a percentage of the overall level of impact, that—in combination—will trigger a health event. By setting a threshold that creates a health event when a score drops below the threshold for one or more city-networks (locations and ASNs, typically ISPs), you can get insights into when there are issues in locations with lower traffic, for example.
An additional local threshold option works together with the local threshold for availability or performance scores. The second factor is the percentage of your overall traffic that must be impacted before Internet Monitor creates a health event based on the local threshold.
By configuring the threshold options for overall traffic and local traffic, you can fine-tune how frequently health events are created, to align with your application usage and your needs. Be aware that when you set the local threshold to be lower, typically more health events are created, depending on your application and the other threshold configuration values that you set.
In summary, you can configure health event thresholds—for performance scores, availability scores, or both—in the following ways:
+ Choose different global thresholds for triggering a health event.
+ Choose different local thresholds for triggering a health event. With this option, you can also change the percentage of impact on your overall application that must be exceeded before Internet Monitor creates an event.
+ Choose to turn off triggering a health event based on local thresholds, or enable local threshold options.
To update health event thresholds for performance scores, availability scores, or both, follow these steps.
**To change threshold configuration options**
1. In the AWS Management Console, navigate to CloudWatch, and then, in the left navigation pane, choose Internet Monitor.
1. On the **Configure** page, in the **Health event thresholds** section, choose **Update thresholds**.
1. On the **Set health event threshold**page, choose the new values and options that you want for thresholds and other options that trigger Internet Monitor to create a health event. You can do any of the following:
+ Choose a new value for **Availability score threshold**, **Performance score threshold**, or both.
The graphs in the sections for each setting display the current threshold setting and the actual recent health event scores, for availability or performance, for your application. By viewing the typical values, you can get an idea of values that you might want to change a threshold to.
Tip: To view a larger graph and change the timeframe, choose the expander in the upper right corner of the graph.
+ Choose to turn on or off a local threshold for availability or performance, or both. When an option is enabled, you can set the threshold and impact level for when you want Internet Monitor to create a health event.
1. After you configure threshold options, save your updates by choosing **Update health event thresholds**.
To learn more about how health events work, see [When Internet Monitor creates and resolves health events](CloudWatch-IM-inside-internet-monitor.md#IMHealthEventStartStop).
# Publish internet measurements to Amazon S3 in Internet Monitor
You can choose to have Internet Monitor publish internet measurements to Amazon S3 for your internet-facing traffic to the monitored city-networks (client locations and ASNs, typically internet service providers) in your monitor, up to the 500,000 city-networks service limit. Internet Monitor automatically publishes internet measurements to CloudWatch Logs every five minutes for the top 500 (by traffic volume) city-networks for each monitor. Measurements that it publishes to S3 include the top 500 that are published to CloudWatch Logs.
You can choose the option to publish to S3, and specify the bucket to publish the measurements, to when you create or update your monitor. The bucket must already be created in S3 before you can specify it in Internet Monitor. There's a service limit of 500,000 city-networks for internet measurements published to S3. Internet Monitor publishes internet measurements to S3 as events, a series of compressed log file objects that are stored in the bucket.
When you create the S3 bucket for Internet Monitor to publish measurements to, make sure that you follow the permissions guidance provided by CloudWatch Logs. Doing so ensures that Internet Monitor can publish logs directly to S3, and that AWS can, if needed, create and change the resource policies associated with the log group receiving the logs. For more information, see [ Logs sent to CloudWatch Logs](https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/AWS-logs-and-resource-policy.html#AWS-logs-infrastructure-CWL) in the Amazon CloudWatch Logs User Guide.
The published log files are compressed. If you open the log files using the Amazon S3 console, they are decompressed and the internet measurement events are displayed. If you download the files, you must decompress them to view the events.
You can also query the internet measurements in the log files using Amazon Athena. Amazon Athena is an interactive query service that makes it easier to analyze data in Amazon S3, by using standard SQL. For more information, see [Use Amazon Athena to query internet measurements in Amazon S3 log files](CloudWatch-IM-view-cw-tools.S3_athena.md).