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Using a Pool of Static IP Addresses, 2.5. Using a Single Static IP Address

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This method is supported and recommended for all deployments. Using some DNS servers, it is even possible to move the maintenance of the PAN addresses out of the applications and into the DNS itself. BIND, the most commonly used DNS server, allows an administrator to enter multiple A records that map a single DNS name to more than one IP address. This again requires static IP addresses, but it enables the application to use a single DNS name for the entire cluster. The DNS server will select one of the defined IP addresses on a round-robin basis. If one of them does not respond, the application must resolve the host name again. 2.2.4. Using a Pool of Static IP Addresses A less desirable approach than either of the preceding is for your application to address a DX Storage cluster using a stored list of several, perhaps all, of the static IP addresses for the nodes in the cluster. This method is supported but not recommended for a production environment. This application's stored list of IP addresses must be accessible programmatically from the application. If one of the nodes fails to respond to a request, then the application can simply try another one. If a redirect response reveals the presence of a storage node not in the original list, the application should be able to add the new IP address to the list. If the cluster is relatively stable with respect to static node IP addresses, this may be a good approach. If, on the other hand, nodes are being added to and removed from the cluster often, you should not use this method. 2.2.5. Using a Single Static IP Address The simplest but least recommended (and least supported) way for an application to address a DX Storage cluster is to assign a static IP address to at least one of the nodes of the cluster and then use that IP address in every request. This method should be used only in a development environment. It can be set up quickly but is not maintainable in a larger system. The simplicity of this approach is balanced by the significant disadvantage that, if the sole PAN is taken out of service or fails completely, the application cannot send requests to the cluster, even though other nodes might still be functioning and all desired content still available. Copyright © 2010 Caringo, Inc. All rights reserved 11 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

This method is supported and recommended for all deployments.

Using some DNS servers, it is even possible to move the maintenance of the PAN addresses out

of the applications and into the DNS itself. BIND, the most commonly used DNS server, allows an

administrator to enter multiple A records that map a single DNS name to more than one IP address.

This again requires static IP addresses, but it enables the application to use a single DNS name

for the entire cluster. The DNS server will select one of the defined IP addresses on a round-robin

basis. If one of them does not respond, the application must resolve the host name again.

2.2.4. Using a Pool of Static IP Addresses

A less desirable approach than either of the preceding is for your application to address a DX

Storage cluster using a stored list of several, perhaps all, of the static IP addresses for the nodes in

the cluster.

This method is supported but not recommended for a production environment.

This application's stored list of IP addresses must be accessible programmatically from the

application. If one of the nodes fails to respond to a request, then the application can simply try

another one.

If a redirect response reveals the presence of a storage node not in the original list, the application

should be able to add the new IP address to the list. If the cluster is relatively stable with respect

to static node IP addresses, this may be a good approach. If, on the other hand, nodes are being

added to and removed from the cluster often, you should not use this method.

2.2.5. Using a Single Static IP Address

The simplest but least recommended (and least supported) way for an application to address a DX

Storage cluster is to assign a static IP address to at least one of the nodes of the cluster and then

use that IP address in every request.

This method should be used

only

in a development environment. It can be set up quickly but is not

maintainable in a larger system.

The simplicity of this approach is balanced by the significant disadvantage that, if the sole PAN is

taken out of service or fails completely, the application cannot send requests to the cluster, even

though other nodes might still be functioning and all desired content still available.