Dell DX6000 Guía de instalación

SCSP Proxy Overview

Version 1.2

SCSP Proxy Overview: Version 1.2

No part of this document may be reproduced, transmitted, or transcribed without the written consent of Caringo, Inc.

December 2010

Table of Contents

1. Introduction ......................................................................................................................... 1

1.1. Basic SCSP Proxy .................................................................................................... 1

1.1.1. Getting a List of DX Storage Cluster IPs .......................................................... 1

1.1.2. About Expect: 100-continue Behavior .............................................................. 3

1.1.3. About Location Headers ................................................................................. 3

1.2. Remote Cluster Communication and Coordination ...................................................... 3

1.2.1. Examples of using /_proxy Syntax ................................................................... 4

1.2.2. Remote Synchronous Writes and Updates ....................................................... 5

1.2.3. Remote Aggregate Info ................................................................................... 5

2. Installing, Configuring and Running SCSP Proxy ................................................................... 8

2.1. Operating System Requirement ................................................................................. 8

2.2. Installing and Configuring the SCSP Proxy ................................................................. 8

2.2.1. Installing SCSP Proxy Prerequisites ................................................................ 8

2.2.2. Upgrading RHEL ............................................................................................ 8

2.2.3. Installing or Upgrading the SCSP Proxy Software ............................................. 8

2.2.4. Configuring the SCSP Proxy ........................................................................... 9

2.3. Running the SCSP Proxy .......................................................................................... 9

2.3.1. Validation Mode ........................................................................................... 10

3. Configuration Parameters ................................................................................................... 13

3.1. Configuring the Proxy by Editing scspproxy.cfg ......................................................... 13

3.2. hosts.cfg ................................................................................................................. 15

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Chapter 1. Introduction

The SCSP Proxy accepts HTTP requests from a host network, forwards them to a DX Storage

cluster, handles redirects transparently, and then supplies the response back to the requestor. In

many deployments, a DX Storage cluster might be isolated on an internal network, protecting it from

undesired interaction with the host network, and also protecting the host network from services like

PXE boot and multicast traffic that can interfere with other network resources.

This reverse proxy can serve several other purposes as well, both in production deployments and in

test environments.

Specifically, the SCSP Proxy supports the following types of interactions:

• Basic SCSP Proxy for a local cluster

• Remote cluster coordination and communication

• Validation of incoming client requests for proper syntax and formatting

1.1. Basic SCSP Proxy

In a local cluster deployment, the SCSP Proxy handles all local SCSP traffic and manages the

associated communication with the local DX Storage cluster. The SCSP Proxy listens for any

inbound SCSP communications on the configured port and determines which DX Storage node to

send the initial request to.

For optimal performance, the SCSP Proxy caches open connections to DX Storage for reuse.

For more information, see one of the following sections:

•Section 1.1.1, “Getting a List of DX Storage Cluster IPs”

•Section 1.1.2, “About Expect: 100-continue Behavior”

•Section 1.1.3, “About Location Headers”

1.1.1. Getting a List of DX Storage Cluster IPs

The SCSP Proxy intercepts GET / and HEAD / requests and responds with information it stores

internally about itself and about the cluster for which it serves as a forward proxy. Only GET / and

HEAD / requests result in this type of special handling by the SCSP Proxy.

Query arguments are not processed, even when the resource is empty. A request with a query

argument is forwarded as-is to the cluster and receives no special processing by the Proxy.

The Proxy responds to a GET / request from a client running in a private network with the Proxy's

list of DX Storage IP addresses and data and metadata describing the Proxy's DX Storage cluster.

You can prevent the Proxy from returning cluster IP addresses using the configuration parameter

reportHosts. For more information about configuration parameters, see Chapter 3, Configuration

Parameters

1.1.1.1. Scsp-Proxy-Cluster Request Header

The optional Scsp-Proxy-Cluster: cluster-name request header, if included with a request,

causes the Proxy to first compare the case-sensitive cluster-name against the Proxy's own

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configured cluster name. If the names do not match, no node IP addresses are returned in the

response.

If Scsp-Proxy-Cluster is not present, the request uses the configured cluster name and the list of

node IP addresses reflects the currently known node IPs for that cluster.

In either case, the response metadata includes a response header with the same name containing

the cluster name used by the Proxy.

1.1.1.2. Response Headers

The following table discusses response headers:

Response Description

Scsp-Proxy-Cluster Cluster name (for example, if the cluster is configured on

a CSN, it is the value of scsp.clusterName in /etc/

caringo/scspproxy/scspproxy.cfg).

Scsp-Proxy-Nodes ASCII string count of the number of node IP addresses

returned in the body of the response. If this count is zero,

an additional reason is supplied to explain why there were

no nodes returned. More information about the zero-node

response is discussed following the table.

Scsp-Proxy-Agent Proxy and its software version.

Castor-System-

TotalGBAvailable, Castor-

System-TotalGBCapacity

Obtained by polling any available node on the local

cluster. These headers are provided to maintain

consistency with current Proxy and DX Storage

responses.

For example, the following response indicates there are 10 nodes in the cluster:

Scsp-Proxy-Nodes: count=10

If the response indicates zero nodes in the cluster, it is accompanied by a reason, as follows:

Scsp-Proxy-Nodes: count=0, reason=no-nodes

The following table discusses reason codes.

Reason for empty node list Meaning

no-nodes The Proxy reports no nodes when, for example, the cluster is

off-line or is being rebooted.

bad-subnet The request was made from a subnet from which the node IP

addresses are not routable.

The Proxy determines whether or not a request originated from

the same private subnet as its cluster and responds only if the

request did originate in that subnet. The Proxy does this to help

prevent malicious discovery about the cluster and because

private IP addresses are not routable anyway.

bad-cluster The cluster name supplied in the Scsp-Proxy-Cluster

header did not match the currently configured cluster.

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Reason for empty node list Meaning

disabled Indicates the Proxy's reportHosts configuration parameter is

set to False.

1.1.1.3. Response Body

The body of the response to a GET / is Content-Type text/plain list of IP addresses of DX Storage

nodes local to that proxy, one address per CRLF-terminated line.

The Content-Length header calculation is based on the number of bytes in this list of CRLF

terminated IPs. If the list is empty, the Scsp-Proxy-Nodes header indicates count=0 and the

Content-Length header is zero.

The body of the response to a HEAD / is always empty, although the Content-Length header

indicates the total number of response bytes that would have been returned if the HEAD had been

a GET. Additionally, the Scsp-Proxy-Nodes header indicates the number of nodes that would have

been returned and, if this count is zero, provides the reason for the empty list exactly as it does for

GET /.

1.1.2. About Expect: 100-continue Behavior

If the initial request includes an Expect: 100-continue header, the SCSP Proxy waits to read

the input stream and won't rewind, seek, or reset it on a WRITE, APPEND, or UPDATE for small

streams until 100-continue is received. If the initial request does not include an Expect: 100-

continue header, the SCSP Proxy buffers input from the client but attempts to stall the input data

object from the client if the buffer reaches a limit. If the request content length is larger than 128K, it

adds Expect: 100-continue to the request it sends to the local cluster and handle DX Storage's

100 response.

1.1.3. About Location Headers

To properly route subsequent requests, the SCSP Proxy returns one Location response header

with its own external IP address and discards any other Location headers. For Replicate on Write

requests, this means all Location response headers are rewritten.

1.2. Remote Cluster Communication and Coordination

Developers who need to interact with multiple DX Storage clusters, either independently or in

multi-cluster requests, can use the SCSP Proxy for remote cluster communication and can even

coordinate requests between more than one cluster at a time.

To use the following syntax, the proxy must be configured with a list of all known remote clusters (for

more information, see Chapter 3, Configuration Parameters). The following syntax is valid only with

the Proxy; sending requests formatted as follows directly to a DX Storage cluster results in a 404

(Not Found) error because DX Storage attempts to resolve it as a path to a named object.

Syntax Description

/_proxy/cluster-name/uuid-or-

name Sends a request for an object, referenced by UUID or

by name, to a specific cluster-name.

/_proxy/any/uuid-or-name any is valid only for remote INFO requests and

results in an error if used with any other method.

any causes a request to be sent for an object,

referenced by UUID or by name, to any available

cluster (local or remote).

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Syntax Description

If the object exists in the local cluster the information

is returned. Otherwise, the request is sent to each

remote cluster in random order. If no cluster is able

to locate the data, the error response from the local

server is returned.

/_proxy/remote/uuid-or-name remote is valid only for remote INFO requests and

results in an error if used with any other method.

remote causes a request for an object to be sent,

referenced by UUID or by name, to a remote cluster.

The information is returned from the first cluster

that has the object. If the object cannot be found in

any of the remote clusters, the error response that

was received from the first remote cluster tried is

returned.

Note

Support for remote proxy requests without the _proxy/ prefix is deprecated in this

release and will be removed altogether in a future release.

1.2.1. Examples of using /_proxy Syntax

As the following examples show, you must separate the URI from the domain specification using the

slash character (/). In all cases, except where noted, the domain name must be passed as the Host

in the request.

Examples follow:

• AggregateInfo of domain on either a local or remote cluster

Local cluster: GET /_proxy/uuid?indirect=HEAD

Remote cluster: GET /_proxy/cluster-name/uuid?indirect=HEAD

For more information about AggregateInfo, see Section 1.2.3, “Remote Aggregate Info”.

• HEAD of a domain on either a remote or any cluster

Remote cluster: HEAD /_proxy/remote?domain=domain-name

Any cluster: HEAD /_proxy/any?domain=domain-name

Note

The domain= query argument is required whenever you perform an operation (in this

case, HEAD) on a domain.

• POST of an unnamed object to the default cluster domain

POST /_proxy/cluster-name/

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Note

Because you are working with the default cluster domain, the domain name does not

need to be sent as the Host in the request. For unnamed objects, POST authentication

is supported only in the default cluster domain.

• Remote synchronous write POST of an unnamed object to the default cluster domain, which has

POST authentication enabled

POST /_proxy/cluster-name/?replicate=immediate

For more information about remote synchronous write, see the next section.

1.2.2. Remote Synchronous Writes and Updates

Remote Synchronous Write enables you to write or update a copy of the same stream both locally

and remotely as part of the same request.

A Remote Synchronous Write first writes two copies of the object to the local cluster. If the local

write fails for any reason, the error response is returned to the requestor and the operation is

abandoned.

If the local write succeeds, the Proxy writes the updated object to the specified remote cluster.

This request is authenticated using the DX Storage administrator credentials specified in the

configuration of the remote cluster.

All query arguments except alias=yes as well as the Expect: Content-MD5 header are stripped

from the remote write to simplify the response coordination between the two clusters.

If the remote write is also successful, a 201 (Created) response is returned to the requestor. If the

remote write fails for any reason, a 202 (Accept) response is returned, indicating that only the local

write was successful and that remote replication can occur at a later time using DX Content Router

(if enabled).

1.2.3. Remote Aggregate Info

The Proxy has an AggregateInfo method to validate that a set of content exists in a cluster.

Aggregate Info can be issued against a local cluster but it is usually used to validate remote

replication.

You determine the desired data set by first creating a "consistency checkpoint" using the following

format, terminated with CRLF:

{uuid [mutable | immutable] | url-encoded-name}

For unnamed anchor streams, you must use mutable parameter. (The default, with no parameter

specified, is immutable.)

All named objects are assumed to be mutable so no argument is required.

You must supply a list of either URL-encoded names or UUIDs. (Use percent encoding for object

names, if needed.) The name, UUID, or the consistency checkpoint, is stored as a DX Storage

object.

Info requests in the AggregateInfo method are issued for each name or UUID in the consistency

checkpoint and either object metadata or an error response is returned in the concatenated

December 2010

response body. Similar to the individual Info method, the response for a successful AggregateInfo

method execution is a 200 code.

The following is a sample checkpoint manifest stream. All object names must be URL-encoded so

you must use percent encoding to escape special characters in named objects, including space. All

line terminators must be CRLF:

1C1AF51688DA4F752CD26E6CD115A6A5

mybucket/photos/marketing/photo.jpg

2AC1961A54575A82CCE115D8F1DA6D6F

12BFEA648C2697A56FD5618CAE15D5CA

training/cloudstorage/videos/mobile/named-objects.3gp

/samples/object%20with%20space.txt

5AE562AC876418F612AA511CDD69F5CD mutable

5DA58EAC74129D116625C611AF5A86DF

The checkpoint manifest should be stored in the local cluster and its name or UUID used to issue

the AggregateInfo request. The AggregateInfo method supports named and unnamed objects

for both the manifests and streams stored in the manifest. It supports authentication only for the

manifest stream itself, and checkpoint streams in the manifests that are protected for HEAD are

returned as 401s in the AggregateInfo response body.

Any additional query arguments and headers included with the AggregateInfo method apply to the

GET request issued for the checkpoint manifest only and are not included in the individual Info

requests for each name or UUID in the manifest. If the checkpoint manifest is stored in an unnamed

anchor stream, the AggregateInfo method must be called with alias=yes in its queryArg

dictionary.

AggregateInfo uses Aggregate-Stream-Count as its trailer header.

Expect: Content-MD5 and Range headers, as well as any integrity seal query arguments, are

not supported for the AggregateInfo method.

1.2.3.1. Aggregate Info Response

For each line of the checkpoint manifest, the SCSP Proxy uses chunked encoding to send in the

AggregateInfo response body either a parse error for the line or the line's name or UUID followed by

the DX Storage's verbatim response for the Info query for it. A CRLF line-end sequence separates

the uuid line from the Info response. For example, for a manifest that included two UUIDs, both of

which the SDK was able to Info successfully, the following representative response body would be

returned:

Response for stream uuid = 64f9e40bfcb7046d79cc02c5876c1904

HTTP/1.1 200 OK

Castor-System-Alias: 64f9e40bfcb7046d79cc02c5876c1904

Castor-System-Cluster: DR Cluster

Castor-System-Created: Tue, 03 Aug 2010 18:49:27 GMT

Castor-System-Version: 1280861367.827

Content-Length: 11

Content-Type: application/x-www-form-urlencoded

Last-Modified: Tue, 03 Aug 2010 18:49:27 GMT

Etag: "aa9ba7fb4648f05c21411cce06c7c3d5"

Date: Tue, 03 Aug 2010 18:49:28 GMT

Server: CAStor Cluster/4.0.2

December 2010

Response for stream uuid = f6a0c60d53dd1047ce670c747b1aba91

HTTP/1.1 200 OK

Castor-System-Cluster: DR Cluster

Castor-System-Created: Tue, 03 Aug 2010 18:49:27 GMT

Content-Length: 11

Content-Type: application/x-www-form-urlencoded

Last-Modified: Tue, 03 Aug 2010 18:49:27 GMT

Etag: "f6a0c60d53dd1047ce670c747b1aba91"

Date: Tue, 03 Aug 2010 18:49:28 GMT

Server: CAStor Cluster/4.0.2

If the first line does not have a valid UUID, the proxy responds with a single error message in the

response body stating that the checkpoint stream is incorrectly formatted and stops processing.

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