Understanding the complicated policies of ASW S3 makes you a superior candidate and an all-around better person.
One of the most popular products from Amazon Web Service (AWS), is Simple Storage Service, popularly abbreviated as S3 . This service provides a durable, highly-available and inexpensive object storage for any kind of object — of any size. Behind S3’s durability and high-availability (HA), there are great engineering practices along with, redundancy and implementation of versioning that makes it very appealing as a web-scale storage service.
Everyone knows about Amazon S3, so discussing here wouldn’t serve us well. Rather, we are going to discuss how objects are stored, and how life-cyles of objects are maintained. I won’t dive into ASW S3 Lifecycle security in this post either. Security represents a crucial part of the developer’s responsibility is an important topic, so I suggest you read Stuart Scott’s post from this winter S3 Lifecycle Policies, Versioning & Encryption: AWS Security.
Storing and maintaining lifecycle objects in AWS S3
We have buckets in S3 and we store objects in them.
- How are these objects managed?
- How are the DR & HA achieved?
- How do objects underneath the storage layer behave when a PUT or DELETE operation is performed?
Let’s talk about S3 Objects and their lifecycle policies.
Amazon S3 achieves high availability by replicating data across multiple servers within Amazon’s data centers. If a PUT request is successful, your data is safely stored. However, information about the changes must replicate across Amazon S3. Also, S3 keeps multiple versions of the Object to achieve HA. Enabling or disabling versioning of one object within the bucket is optional. If you enable versioning, you can protect your objects from accidental deletion or being overwritten because you have the option of retrieving older versions of them.
Object versioning can be used in combination with Object Lifecycle Management, which allows you the option of customizing your data retention requirements while controlling your storage costs.
When you PUT an object in a versioning-enabled bucket, the noncurrent version is not overwritten. Rather, when a new version of a file or an object is PUT into a bucket that already contains an object with the same name, the original object remains in the bucket, and Amazon S3 generates a new version ID. Amazon S3 then adds the newer version to the bucket. This service is automatically performed by S3 so that, as a user, your only concern is enabling and disabling the versioning in the bucket.
Amazon S3 also provides resources for managing lifecycle by user need. For example, if you want to move less frequently accessed data to Glacier, or set a rule to delete the file (e.g. old log files of an application stored in a bucket) after a specified interval of time, you can easily automate the process. AWS allows the enabling of up-to 100 lifecycle rules for achieving control of your objects in S3 buckets.
Configuring Amazon S3 Lifecycle:
Amazon S3 Lifecycle configurations are provided by means of XML. A typical configuration looks like this:
<LifecycleConfiguration> <Rule> <ID> cloudacademy-image-rule</ID> <Prefix>cloudacademyblogimg/</Prefix> <Status>Enabled</Status> <Transition> <Days>90</Days> <StorageClass>GLACIER</StorageClass> </Transition> <Expiration> <Days>365</Days> </Expiration> </Rule> </LifecycleConfiguration>
Here we have defined an S3 lifecycle configuration for objects in a bucket. We have images in a bucket stored in the folder named cloudacademyblogimg and we want to move them to GLACIER storage every 30 days. Glacier is another useful service from Amazon allowing inexpensive, highly durable storage services for archiving huge volumes of data. After a year of storage, we will likely delete it. Let’s look at the various metadata associated with it:
- LifecycleConfiguration – A LifecycleConfiguration defines a rule that applies to an object with a key.
- ID– The ID element uniquely identifies a rule. A lifecycle configuration can have up to 1000 rules.
- Prefix – Prefix are the Object keys. If in an S3 bucket named cloudacademyblog we have a folder called cloudacademyblogimg, and an image is named S3_thumbnail.gif inside that folder, then the Object key is cloudacademyblogimg/S3_thumbnail.gif. If you do not specify the Prefix, the rule will be applied to all the objects in the bucket.
- Status – Enabled or Disabled.
- Transition – Transition is one of the lifecycle actions of S3. This transition action specifies you want to move the objects from one storage class to another. There are three storage classes in S3 named, STANDARD, STANDARD-IA (IA denotes Infrequent Access) and GLACIER. Here we have mentioned GLACIER, where files will be moved after 90 days. You can either specify the number of days or a specific date (but you cannot use both).
- Expiration – The Expiration action specifies when the objects expire. In this case, we have specified a period of 365 days, or one year. There are several considerations for the expiration rules. These rules might seem a bit confusing at first, so please be patient and read along. They will eventually make sense and you can refer back to them frequently. A good understanding of this concept will take you a long way while working with S3.
- In a non-versioned bucket, the Expiration action results in Amazon S3 permanently removing the object.
- The expiration action applies only to the current version. In a versioned bucket, S3 will not take any action if there are one or more object versions and the delete marker is the current version.
- If the current object version is the only object version and it is also a delete marker, S3 will remove the expired object delete marker.
- If current object version is not a delete marker, Amazon S3 adds a delete marker with a unique version ID, making the current version noncurrent, and the delete marker the current version.
- For non-current version objects, there is an action named NoncurrentVersionTransition action element, which is used to specify how long (from the time the objects became noncurrent) users want the objects to remain in the current storage class before Amazon S3 transitions them to the specified storage class.
- There is also a NoncurrentVersionExpiration action for non-current version objects that specify how long (from the time the objects became noncurrent) user want to retain noncurrent object versions before Amazon S3 permanently removes them. In this case, the deleted object cannot be recovered.
- Starting from March 16th, 2016, Amazon S3 introduced “incomplete multipart upload expiration policy”.
- If a multi-part upload is incomplete, the partial upload does not appear when users list their objects by default. However, this does incur storage charges.
- Previously, you needed to manually cancel the multi-part upload to remove partial uploads.
- Now, users can set a lifecycle policy to automatically expire and remove incomplete multi-part uploads after a predefined number of days.
- The policy applies to everything in a bucket, including existing partial uploads. The rule looks like this:
<LifecycleConfiguration> <Rule> <ID>multipart-upload-rule</ID> <Prefix></Prefix> <Status>Enabled</Status> <AbortIncompleteMultipartUpload> <DaysAfterInitiation>3</DaysAfterInitiation> </AbortIncompleteMultipartUpload> </Rule> </LifecycleConfiguration>
- Always remember that the “last modified date” of an object is treated as the starting date for the lifecycle of that object in S3. If you replace the object, the new date is considered the creation date.
- If an object is marked as non-current, due to it being overwritten or deleted, S3 will take action on that object(s) since it transitioned to non-current.
- You can specify multiple rules for different lifecycle action on objects. Take a look at this rule:
- One rule acts on where the images in cloudacademyblogimg are moved to GLACIER after 30 days and removed after 365 days.
- The other rule specifies that the logs-in will be transitioned to Standard Infrequent access storage class (STANDARD_IA), after 7 days and deleted after 30 days.
<LifecycleConfiguration> <Rule> <ID>CAImgRule</ID> <Prefix>cloudacademyblogimg/</Prefix> <Status>Enabled</Status> <Transition> <Days>90</Days> <StorageClass>GLACIER</StorageClass> </Transition> <Expiration> <Days>365</Days> </Expiration> </Rule> <Rule> <ID> CALogRule</ID> <Prefix> cloudacademylogs/</Prefix> <Status>Enabled</Status> <Transition> <Days>30</Days> <StorageClass>STANDARD_IA</StorageClass> </Transition> <Expiration> <Days>30</Days> </Expiration> </Rule> </LifecycleConfiguration>
- The lifecycle rule is applied through AWS CLI as follows:
aws s3api put-bucket-lifecycle --bucket bucketname --lifecycle-configuration filename-containing-lifecycle-configuration
Applying Lifecycle rules in AWS Management Console:
- Login to the S3 in AWS Management Console.
- Navigate to the bucket that you want to apply Lifecycle rules.
- Click on the Lifecycle link on the right-hand side of the Properties tab, and click on “Add rule”.
- You can either apply the rule to the whole bucket or any folder (prefix). We selected cpimg/ to apply Lifecycle rules in this example. Click on “Configure Rule”.
- We have provided 30 days for Transition and 365 days for Expiration to the objects. We also specified 2 days for incomplete multipart uploads.
- Then Review, Create & Activate Rule.
- If the rule does not contain any errors, it is displayed in the Lifecycle pane.
Mastering ASW S3 policies and exceptions requires considerable energy. Cloud Academy can help. They offer a suite of products for developers learning ASW S3.
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When you review this post, you’ll see we used the AWS Management Console to create and activate a rule. In a professional setting, a developer will likely require far more complex rules. This is more an opportunity than a challenge because there are tremendously good learning resources around AWS S3. Treat yourself to a free 7-day trial subscription to Cloud Academy where the above resources are all available. Training, personal determination, and AWS S3 documentation present a winning combination for career advancement.