Module: rds-cloudwatch-sns-alarms

Terraform module that configures important RDS alerts using CloudWatch and sends them to an SNS topic.

Create a set of sane RDS CloudWatch alerts for monitoring the health of an RDS instance.

Usage

area	metric	comparison operator	threshold	rationale
Storage	BurstBalance	<	20 %	20 % of credits allow you to burst for a few minutes which gives you enough time to a) fix the inefficiency, b) add capacity or c) switch to io1 storage type.
Storage	DiskQueueDepth	>	64	This number is calculated from our experience with RDS workloads.
Storage	FreeStorageSpace	<	2 GB	2 GB usually provides enough time to a) fix why so much space is consumed or b) add capacity. You can also modify this value to 10% of your database capacity.
CPU	CPUUtilization	>	80 %	Queuing theory tells us the latency increases exponentially with utilization. In practice, we see higher latency when utilization exceeds 80% and unacceptable high latency with utilization above 90%
CPU	CPUCreditBalance	<	20	One credit equals 1 minute of 100% usage of a vCPU. 20 credits should give you enough time to a) fix the inefficiency, b) add capacity or c) don't use t2 type.
Memory	FreeableMemory	<	64 MB	This number is calculated from our experience with RDS workloads.
Memory	SwapUsage	>	256 MB	Sometimes you can not entirely avoid swapping. But once the database accesses paged memory, it will slow down.

Examples

See the examples/ directory for working examples.

resource "aws_db_instance" "default" {
  allocated_storage    = 10
  storage_type         = "gp2"
  engine               = "mysql"
  engine_version       = "5.7"
  instance_class       = "db.t2.micro"
  identifier_prefix    = "rds-server-example"
  name                 = "mydb"
  username             = "foo"
  password             = "foobarbaz"
  parameter_group_name = "default.mysql5.7"
  apply_immediately    = "true"
  skip_final_snapshot  = "true"
}

module "rds_alarms" {
  source         = "git::https://github.com/cloudposse/terraform-aws-rds-cloudwatch-sns-alarms.git?ref=tags/0.1.5"
  db_instance_id = "${aws_db_instance.default.id}"
}

Variables

Required Variables

db_instance_id (string) required

The instance ID of the RDS database instance that you want to monitor.

Optional Variables

burst_balance_threshold (number) optional

The minimum percent of General Purpose SSD (gp2) burst-bucket I/O credits available.

Default value: 20

cpu_credit_balance_threshold (number) optional

The minimum number of CPU credits (t2 instances only) available.

Default value: 20

cpu_utilization_threshold (number) optional

The maximum percentage of CPU utilization.

Default value: 80

disk_queue_depth_threshold (number) optional

The maximum number of outstanding IOs (read/write requests) waiting to access the disk.

Default value: 64

free_storage_space_threshold (number) optional

The minimum amount of available storage space in Byte.

Default value: 2000000000

freeable_memory_threshold (number) optional

The minimum amount of available random access memory in Byte.

Default value: 64000000

swap_usage_threshold (number) optional

The maximum amount of swap space used on the DB instance in Byte.

Default value: 256000000

Context Variables

The following variables are defined in the context.tf file of this module and part of the terraform-null-label pattern.

additional_tag_map (map(string)) optional

Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id.
This is for some rare cases where resources want additional configuration of tags
and therefore take a list of maps with tag key, value, and additional configuration.

Required: No

Default value: { }

attributes (list(string)) optional

ID element. Additional attributes (e.g. workers or cluster) to add to id,
in the order they appear in the list. New attributes are appended to the
end of the list. The elements of the list are joined by the delimiter
and treated as a single ID element.

Required: No

Default value: [ ]

context (any) optional

Single object for setting entire context at once.
See description of individual variables for details.
Leave string and numeric variables as null to use default value.
Individual variable settings (non-null) override settings in context object,
except for attributes, tags, and additional_tag_map, which are merged.

Required: No

Default value:

{
  "additional_tag_map": {},
  "attributes": [],
  "delimiter": null,
  "descriptor_formats": {},
  "enabled": true,
  "environment": null,
  "id_length_limit": null,
  "label_key_case": null,
  "label_order": [],
  "label_value_case": null,
  "labels_as_tags": [
    "unset"
  ],
  "name": null,
  "namespace": null,
  "regex_replace_chars": null,
  "stage": null,
  "tags": {},
  "tenant": null
}

delimiter (string) optional

Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.

Required: No

Default value: null

descriptor_formats (any) optional

Describe additional descriptors to be output in the descriptors output map.
Map of maps. Keys are names of descriptors. Values are maps of the form
\{<br/> format = string<br/> labels = list(string)<br/> \}
(Type is any so the map values can later be enhanced to provide additional options.)
format is a Terraform format string to be passed to the format() function.
labels is a list of labels, in order, to pass to format() function.
Label values will be normalized before being passed to format() so they will be
identical to how they appear in id.
Default is {} (descriptors output will be empty).

Required: No

Default value: { }

enabled (bool) optional

Set to false to prevent the module from creating any resources
Required: No

Default value: null

environment (string) optional

ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'
Required: No

Default value: null

id_length_limit (number) optional

Limit id to this many characters (minimum 6).
Set to 0 for unlimited length.
Set to null for keep the existing setting, which defaults to 0.
Does not affect id_full.

Required: No

Default value: null

label_key_case (string) optional

Controls the letter case of the tags keys (label names) for tags generated by this module.
Does not affect keys of tags passed in via the tags input.
Possible values: lower, title, upper.
Default value: title.

Required: No

Default value: null

label_order (list(string)) optional

The order in which the labels (ID elements) appear in the id.
Defaults to ["namespace", "environment", "stage", "name", "attributes"].
You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.

Required: No

Default value: null

label_value_case (string) optional

Controls the letter case of ID elements (labels) as included in id,
set as tag values, and output by this module individually.
Does not affect values of tags passed in via the tags input.
Possible values: lower, title, upper and none (no transformation).
Set this to title and set delimiter to "" to yield Pascal Case IDs.
Default value: lower.

Required: No

Default value: null

labels_as_tags (set(string)) optional

Set of labels (ID elements) to include as tags in the tags output.
Default is to include all labels.
Tags with empty values will not be included in the tags output.
Set to [] to suppress all generated tags.
Notes:
The value of the name tag, if included, will be the id, not the name.
Unlike other null-label inputs, the initial setting of labels_as_tags cannot be
changed in later chained modules. Attempts to change it will be silently ignored.

Required: No

Default value:

[
  "default"
]

name (string) optional

ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'.
This is the only ID element not also included as a tag.
The "name" tag is set to the full id string. There is no tag with the value of the name input.

Required: No

Default value: null

namespace (string) optional

ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique
Required: No

Default value: null

regex_replace_chars (string) optional

Terraform regular expression (regex) string.
Characters matching the regex will be removed from the ID elements.
If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.

Required: No

Default value: null

stage (string) optional

ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'
Required: No

Default value: null

tags (map(string)) optional

Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.

Required: No

Default value: { }

tenant (string) optional

ID element (Rarely used, not included by default). A customer identifier, indicating who this instance of a resource is for
Required: No

Default value: null

Outputs

sns_topic_arn

The ARN of the SNS topic

Dependencies

Requirements

• terraform, version: >= 0.13.0
• aws, version: >= 2.0

Providers

• aws, version: >= 2.0

Modules

Name	Version	Source	Description
label	0.25.0	cloudposse/label/null	n/a
subscription_label	0.25.0	cloudposse/label/null	n/a
this	0.25.0	cloudposse/label/null	n/a
topic_label	0.25.0	cloudposse/label/null	n/a

Resources

The following resources are used by this module:

• aws_cloudwatch_metric_alarm.burst_balance_too_low (resource)
• aws_cloudwatch_metric_alarm.cpu_credit_balance_too_low (resource)
• aws_cloudwatch_metric_alarm.cpu_utilization_too_high (resource)
• aws_cloudwatch_metric_alarm.disk_queue_depth_too_high (resource)
• aws_cloudwatch_metric_alarm.free_storage_space_too_low (resource)
• aws_cloudwatch_metric_alarm.freeable_memory_too_low (resource)
• aws_cloudwatch_metric_alarm.swap_usage_too_high (resource)
• aws_db_event_subscription.default (resource)
• aws_sns_topic.default (resource)
• aws_sns_topic_policy.default (resource)

Data Sources

The following data sources are used by this module:

• aws_caller_identity.default (data source)
• aws_iam_policy_document.sns_topic_policy (data source)