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Replication, 4.2. Deletion

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16.4.1. Replication The ReplicationConstraintSpecialist maintains the desired level of redundancy of content objects, as well as making sure they are being stored in the most efficient manner possible. ReplicationConstraintSpecialist understands one constraint name: reps, which can be set to any integer value. ReplicationConstraintSpecialist does this by making sure that, at all times, the actual number of replicas for an object is equal to reps. If a replication constraint is missing from the lifepoint, a default value is supplied from the node or cluster configuration parameters. However, the cluster administrator can place additional limits on the number of replicas that can be specified by defining minreps and/or maxreps in the node or cluster configuration file. If invalid or conflicting values of the reps constraint are found in a lifepoint, they are ignored, defaults are used, and warnings are written to the log. Note If there is one replica of an object in a cluster, then there is one instance of that object. Replica, instance and object are all synonymous in this usage. It would also be correct to say that there is one instance of the object in the cluster. 16.4.2. Deletion The DeletionConstraintSpecialist completely removes a content object at a certain point in time, and allows or disallows client applications to delete the content object using the SCSP DELETE request. DeletionConstraintSpecialist understands two constraint names: deletable and delete. Constraint name deletable delete Description Can be set to yes|true or no|false. • yes|true (default) means that normally an object is deletable by any client that knows its name or UUID. The DELETE method must also be included in the Allow header for a client delete to be allowed. • no|false prevents any agent outside of DX Storage from deleting the object during the effective period of the lifepoint. Any attempt to delete the object result in a 403 (Forbidden) response. Does not accept a value. Causes DeletionConstraintSpecialist to delete the content object from the cluster. The result is the same as if a client application had deleted the object. To avoid ambiguity, when delete is present in a lifepoint specification, it must be the only constraint in that lifepoint because other conditions on a deleted object are likely not applicable. Furthermore, a delete lifepoint must be specified with an empty end date as shown in the following example. Copyright © 2010 Caringo, Inc. All rights reserved 62 Version 5.0 December 2010

Section	Page
DX Object Storage Application Guide	1
Table of Contents	3
Chapter 1. Introduction to DX Storage Objects	6
1.1. Introducing Named Objects	6
1.2. Summary of Named Objects and Unnamed Objects	7
1.3. Common Named Object Terminology	7
1.4. About DX Storage Object Types	8
1.5. Bucket and Object Naming Rules	8
1.6. Simple Examples of Creating Buckets and Named Objects	8
1.7. Universal Resource Identifiers (URIs)	9
1.8. About Objects and Security	10
1.8.1. The Basics of DX Storage Security	10
1.8.2. Commonly Used Security Terminology	11
1.8.3. Basic Security Guidelines	11
1.9. Concepts for Unnamed Objects	11
1.9.1. Universally Unique Identifiers (UUIDs)	11
1.9.2. About Immutable Objects	12
1.9.3. About Anchor Streams	12
1.10. Document Typographical Conventions	13
Chapter 2. Connecting to a DX Storage Cluster	14
2.1. About the Primary Access Node (PAN)	14
2.2. Requirements for Node Accessibility	14
2.2.1. Using the DX Storage Software Development Kit (SDK)	14
2.2.2. Using Multicast-DNS (mDNS)	15
2.2.3. Using DNS Round Robin	15
2.2.4. Using a Pool of Static IP Addresses	16
2.2.5. Using a Single Static IP Address	16
Chapter 3. Application Best Practices	17
3.1. Using the Software Development Kit (SDK)	17
3.2. Dynamically Locating DX Storage Nodes	17
3.3. Optimizing Bucket and Domain Operations	17
3.4. Using HTTP Client Libraries	17
3.5. Handling Redirects	18
3.6. Using Range Headers	18
3.7. Multi-Threading	19
3.8. Using Persistent Connections	19
Chapter 4. Introduction to the Simple Content Storage Protocol (SCSP)	20
4.1. Mapping SCSP Operations to HTTP Methods	20
4.2. HTTP Overview	21
4.3. Requests and Responses	21
4.3.1. HTTP Response Codes	21
4.3.2. Redirect Responses	22
4.4. Formatting SCSP Commands for Named and Unnamed Objects	22
4.5. Undefined Responses from DX Storage	23
4.6. Normal Response Headers	24
Chapter 5. SCSP READ	27
5.1. Introduction to READ	27
5.1.1. Reading With Content Validation	27
5.1.2. Requestion Node Status and Cluster Capacity	27
5.2. Unnamed Object READ Details	28
5.3. Normal Responses to READ	28
5.3.1. Normal READ Responses for Named Objects	28
5.3.1.1. Normal READ Response for a Domain	28
5.3.1.2. Normal READ Response for a Bucket	29
5.3.1.3. Normal READ Response for a Named Object	29
5.3.2. Normal READ Response for Unnamed Objects	29
5.3.3. Other Normal READ Responses	30
5.4. Error Responses to READ	30
Chapter 6. SCSP WRITE	32
6.1. Introduction to WRITE	32
6.1.1. About the Expect: 100-continue Header and WRITE	33
6.1.2. About Replicate On Write	33
6.2. Named Object WRITE Details	33
6.3. Unnamed Object WRITE Details	33
6.4. Normal Responses to WRITE	33
6.5. Error Responses to WRITE	34
Chapter 7. SCSP DELETE	36
7.1. Introduction to DELETE	36
7.2. Unnamed Object DELETE Details	37
7.3. Named Object DELETE Details	37
7.4. Normal Responses to DELETE	37
7.5. Error Responses to DELETE	38
Chapter 8. SCSP UPDATE	39
8.1. Introduction to UPDATE	39
8.2. Unnamed Object UPDATE Details	39
8.3. Normal Responses to UPDATE	40
Chapter 9. SCSP COPY	41
9.1. Introduction to COPY	41
9.2. Unnamed Object COPY Details	41
9.3. Normal Responses to COPY	41
Chapter 10. SCSP APPEND	42
10.1. Introduction to APPEND	42
10.2. Unnamed Object APPEND Details	43
10.3. Normal Responses to APPEND	43
Chapter 11. SCSP INFO	44
11.1. Introduction to INFO	44
11.1.1. Getting Replica Counts	44
11.1.2. Getting Node Status and Cluster Capacity	44
11.2. Unnamed Object INFO Details	45
11.3. Normal Responses to INFO	45
11.3.1. Normal INFO Responses for Named and Unnamed Objects	45
11.3.2. Normal INFO Responses for Named Objects	46
11.3.3. Normal INFO Responses for Unnamed Objects	47
11.4. Error Responses to INFO	47
Chapter 12. Introduction to Object Security	48
12.1. About Security Roles	48
12.2. Security Realm Overview	49
12.2.1. Common Security Terminology	49
12.2.2. About Security Realms	49
12.2.3. About Realm Caching and Security	49
12.3. About Authorization Header Syntax	50
12.3.1. About Realm Names	51
12.3.1.1. About Realms and Buckets	51
12.3.1.2. About owner@ and @owner Syntax	51
12.3.1.3. About user@realm Syntax	51
12.4. Authorization Specification Examples	51
12.5. About Authorization Header Evaluation	52
12.6. Creating Realms	53
12.7. Updating the Realm on a Bucket	54
12.8. Administrative Override and Security	54
Chapter 13. Managing Security for Application Developers	55
13.1. What Application Developers Need to Know	55
13.2. About Bucket Authorization	55
13.3. Example: Creating Bucket Owners	56
13.4. Examples of Creating Buckets and Named Objects	56
Chapter 14. Managing Security for Domain Managers	59
14.1. What Domain Managers Need to Know	59
14.2. About Domain Manager Tasks and Responsibilities	59
14.3. Examples of Updating Domain and Administrator User Lists	59
14.3.1. Updating the Domain Realm	60
14.3.2. Updating the Domain Manager Realm	61
14.3.3. Updating a Realm Using PUT	62
Chapter 15. Using the Content-MD5 Metadata Header	64
Chapter 16. Using Lifepoint Metadata Headers	65
16.1. About Storage Policies	65
16.2. A Simple Lifecycle Example	65
16.3. Lifepoint/Lifecycle Specification	66
16.4. Constraint Types	66
16.4.1. Replication	67
16.4.2. Deletion	67
Chapter 17. Using the Allow Metadata Header	69
17.1. Overview of the Allow Header	69
17.2. Administrative Override	69
Chapter 18. Using Caching Metadata Headers	71
18.1. About Caching Headers	71
18.2. Using HTTP/1.0 Caching Headers	71
18.2.1. Last-Modified	71
18.2.2. If-Modified-Since	71
18.2.3. If-Unmodified-Since	71
18.2.4. Expires	72
18.3. Using HTTP/1.1 Caching Headers	72
18.3.1. ETag	72
18.3.2. If-Match	72
18.3.3. If-None-Match	73
18.3.4. If-Range	73
Chapter 19. Using Custom Metadata Headers	75
Chapter 20. Basic Content Integrity Assurance	76
20.1. Integrity Seals	76
20.2. Validating Reads	76
20.3. Application Initiated Hash Upgrading	77
Appendix A. Content Header Metadata	78
Appendix B. Sample Code and Client Library Behaviors with 100-Continue	80

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Version 5.0

December 2010

16.4.1. Replication

The

ReplicationConstraintSpecialist

maintains the desired level of redundancy of

content objects, as well as making sure they are being stored in the most efficient manner possible.

ReplicationConstraintSpecialist

understands one constraint name:

reps

, which can be

set to any integer value.

ReplicationConstraintSpecialist

does this by making sure that, at all times, the actual

number of replicas for an object is equal to

reps

. If a replication constraint is missing from the

lifepoint, a default value is supplied from the node or cluster configuration parameters.

However, the cluster administrator can place additional limits on the number of replicas that can be

specified by defining

minreps

and/or

maxreps

in the node or cluster configuration file. If invalid or

conflicting values of the

reps

constraint are found in a lifepoint, they are ignored, defaults are used,

and warnings are written to the log.

Note

If there is one replica of an object in a cluster, then there is one instance of that object.

Replica, instance and object are all synonymous in this usage. It would also be correct to

say that there is one instance of the object in the cluster.

16.4.2. Deletion

The

DeletionConstraintSpecialist

completely removes a content object at a certain point

in time, and allows or disallows client applications to delete the content object using the SCSP

DELETE request.

DeletionConstraintSpecialist

understands two constraint names:

deletable

and

delete

Constraint name

Description

deletable

Can be set to

yes

true

false

•

yes

true

(default) means that normally an object is deletable by any

client that knows its name or UUID. The DELETE method must also be

included in the Allow header for a client delete to be allowed.

•

false

prevents any agent outside of DX Storage from deleting the

object during the effective period of the lifepoint. Any attempt to delete

the object result in a 403 (Forbidden) response.

delete

Does not accept a value.

Causes

DeletionConstraintSpecialist

to delete the content

object from the cluster. The result is the same as if a client application

had deleted the object.

To avoid ambiguity, when

delete

is present in a lifepoint specification, it

must be the only constraint in that lifepoint because other conditions on a

deleted object are likely not applicable. Furthermore, a

delete

lifepoint

must be specified with an empty end date as shown in the following

example.