The gSOAP Toolkit
Robert van Engelen
Kyle Gallivan
Florida State University
IEEE CCGrid May 22, 2002
1
Overview
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Web Services
gSOAP design and implementation
Results
Conclusions
IEEE CCGrid May 22, 2002
2
Web Services:
the Big Picture
SOAP
DSIG
WSDL
UDDI
SOAP RPC
IEEE CCGrid May 22, 2002
3
SOAP
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Light-weight protocol based on XML as
the marshalling format for data in request
and response messages
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Vendor- and platform-neutral
Language-neutral
Object-model-neutral
Transport-neutral
XML allows data transformation (XSLT)
XML enables long-term data persistence
IEEE CCGrid May 22, 2002
4
WSDL
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IEEE CCGrid May 22, 2002
Web Service
registers with
UDDI
Web Service
publishes WSDL
Clients can
develop proxies
from the WSDL
for SOAP RPC
and messaging
5
gSOAP
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Open source (C, C++, and Java)
>2000 registered users
Uses a source-to-source stub and
skeleton compiler to automate the
integration of SOAP RPC in applications
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Automates the deployment of (legacy)
C/C++ applications as Web Services
Automates the development of clients
Suitable for high-performance computing
IEEE CCGrid May 22, 2002
6
gSOAP Goals
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Application-centric
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Minimize application code adaptation
Support (de)marshalling of application’s
native data structures in SOAP/XML
Preserve the logical structure of data
Minimize data migration overhead and
formatting errors
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Avoid (hand-written) wrappers
Generate fast (de)marshalling routines
and streaming XML parsers
Efficient run-time remote object allocation
IEEE CCGrid May 22, 2002
7
The gSOAP Stub and
Skeleton Compiler
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User application
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gSOAP-generated
Stub/Skeleton and
Marshalling Code
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Runtime Library
HTTP/TCP/SOAP
and XML API
Generates source code stubs and
skeletons for SOAP RPC
Generates XML (de)marshalling
routines for native and userdefined C/C++ data types
The gSOAP runtime provides lowlevel HTTP, TCP, SOAP/XML
handling and memory
management capabilities
IEEE CCGrid May 22, 2002
8
Server Development
Service
Application
Specification of
Data Types and
Remote Procedures
in C/C++ Header File
gSOAP-generated
Skeleton Routines
gSOAP
Compiler
gSOAP-generated
Request Dispatcher
WSDL
IDL
IEEE CCGrid May 22, 2002
9
Development Client
Specification of
Data Types and
Remote Procedures
in C/C++ Header File
Client Application
gSOAP
gSOAP-generated
Stub Routines
WSDL
IDL
IEEE CCGrid May 22, 2002
10
Example
Service description (WSDL):
Namespace: urn:xmethods-delayed-quotes
Method name: getQuote
Input parameter: symbol of type xsd:string
Output parameter: result of type xsd:float
Generated remote procedure declaration for stub generation with gSOAP:
ns__getQuote(char *symbol, float &result);
Client code:
main()
{ float q;
if (soap_call_ns__getQuote(“URL”, “”, “AOL”, q) == 0)
cout << “AOL: “ << q << endl;
}
IEEE CCGrid May 22, 2002
11
Encoding C/C++ Data
Types in XML
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Primitive C/C++ types, enum,
struct/class with single inheritance,
pointers, arrays, special types (e.g.
base64)
Not supported: unions, void*,
templates, multiple inheritance
IEEE CCGrid May 22, 2002
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Serialization
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gSOAP generates serialization
routines for application types
Serialization code traverses object
graph at run time to detect coreferenced objects and cycles
Serialization code outputs object
graph in XML according to SOAP
encoding rules
IEEE CCGrid May 22, 2002
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Serialization Example
struct BG
{ int val;
struct BG *left;
struct BG *right;
};
1
2
3
<BG>
<val>1</val>
<left>
<val>2</val>
<right href=“#X”/>
</left>
<right href=“#X”/>
</BG>
<id id=“X”>
<val>3</val>
<right href=“#X”/>
</id>
IEEE CCGrid May 22, 2002
14
Deserialization
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gSOAP generates deserialization code,
including schema-driven XML pull parser
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Auto-validating
Streaming
Fast: match inbound XML elements to
“expected” elements in the schema
Keep table with “forward” XML refs
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Back-patching method: resolve forward
refs later by copying pointers and/or
referenced data
IEEE CCGrid May 22, 2002
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Deserialization Example
<BG>
<val>1</val>
<left>
<val>2</val>
<right href=“#X”/>
</left>
<right href=“#X”/>
</BG>
<id id=“X”>
<val>3</val>
<right href=“#X”/>
</id>
1
2
IEEE CCGrid May 22, 2002
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16
Results
1.
2.
3.
Interoperability testing
Legacy code integration
Scalability and performance
IEEE CCGrid May 22, 2002
17
Interoperability Testing
String Integer Float Struct
String
Array
Integer Float
Array Array
Struct
Array
Void Base64 Date
Hex
Decimal Boolean Map
Binary
Map
Array
gSOAP
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
PASS
PASS
SOAP::Lite
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
PASS
FAULT
Apache 2.2
PASS PASS PASS PASS FAULT PASS
FAULT FAULT PASS PASS PASS
PASS
PASS
PASS
PASS
PASS
Apache Axis PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS FAIL
FAULT PASS
PASS
PASS
PASS
ASP .NET
PASS PASS PASS PASS FAIL
PASS
PASS
FAIL
PASS PASS PASS
FAULT PASS
PASS
N/A
N/A
Cape
Connect
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
Delphi
PASS PASS PASS PASS FAIL
PASS
PASS
FAULT PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
easySOAP++ PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
eSOAP
PASS PASS PASS PASS FAIL
PASS
PASS
FAIL
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
Frontier
PASS PASS PASS PASS FAULT FAULT FAULT FAULT PASS PASS FAIL
FAULT FAULT FAULT N/A
N/A
GLUE
PASS PASS PASS PASS FAIL
PASS PASS FAIL
PASS
PASS
PASS
N/A
N/A
MS SOAP
3.0
PASS PASS PASS PASS FAULT PASS
FAULT FAULT PASS PASS FAIL
PASS
PASS
PASS
N/A
N/A
nuSOAP
PASS PASS PASS PASS FAIL
PASS
PASS
FAIL
PASS PASS PASS
PASS
PASS
PASS
FAULT FAULT
OpenLink
Virtuoso
PASS PASS PASS PASS FAIL
PASS
PASS
FAIL
PASS PASS PASS
PASS
PASS
PASS
N/A
PEAR SOAP PASS PASS PASS PASS FAIL
PASS
PASS
FAIL
PASS PASS FAULT PASS
FAIL
PASS
FAULT FAULT
SOAP4R
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
PASS
PASS
Spheon
jSOAP
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
PASS
PASS
Spray
PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
SQLData
PASS PASS PASS PASS PASS
PASS
FAULT FAULT PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
WASP Adv. PASS PASS PASS PASS PASS
PASS
PASS
PASS
PASS
FAIL

N/A
PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
White Mesa PASS PASS PASS PASS FAULT PASS
FAULT PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
XMLBus
PASS PASS PASS PASS PASS
PASS
PASS
PASS PASS PASS
PASS
PASS
PASS
N/A
N/A
4S4C 2.0
PASS PASS PASS PASS PASS
PASS
FAULT PASS
PASS PASS FAULT FAULT PASS
PASS
N/A
N/A
PASS
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IEEE CCGrid May 22, 2002
WhiteMesa.org
“interop lab”
Suite of test
cases designed
for real-time
interoperability
testing over the
Web
Apache Axis,
.NET, Delphi,…
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Legacy Code Example:
Linear System Solver
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Application code
from Numerical
Recipes in C
Web Service:
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IEEE CCGrid May 22, 2002
LU
Decomposition
Backsubstitution
Solve
Multi-solve
Matrix inversion
19
Linear System Solver
Original Numerical Recipes in C routine:
ludcmp(double **a, int n, int *indx, double *d)
{ … sum = a[i][j]; … }
Modified routine (array size n stored in class instances):
ludcmp(matrix *a, ivector *indx, double *d)
{ … sum = a[i][j]; … }
C++ class declarations for the generation of (de)serializers with gSOAP:
class vector
{ double *__ptr;
// pointer to array of double
int __size;
// run-time array size
double& operator[](int i);
};
class matrix
{ vector *__ptr;
// pointer to array of vectors
int __size;
// run-time array size
double& operator[](int i);
};
IEEE CCGrid May 22, 2002
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Linear System Solver
Remote procedure declaration for stub and skeleton generation with gSOAP:
ns__ludcmp
( matrix *a,
// input matrix
struct ns__ludcmpResponse
{ matrix *a;
// output matrix
ivector *i;
// output index reordering vector
double d;
// output parameter for determinant
} *result
)
Remote procedure SOAP server interface routine called by skeleton:
ns__ludcmp(matrix *a, struct ns__ludcmpResponse &result)
{ result.a = a;
// input to output matrix
if (ludcmp(result.a, result.i, &result.d) != 0)
return SOAP_FAULT;
return SOAP_OK;
}
IEEE CCGrid May 22, 2002
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Linear System Solver
Linear system solver server code (CGI-based):
main()
{ soap_serve(); // process request (skeletons)
}
Example client code:
main()
{ struct ns__ludcmpResponse result;
matrix a;
…
if (soap_call_ns__ludcmp(“URL”, “”, &a, &result) != 0)
soap_print_fault(stderr);
…
}
IEEE CCGrid May 22, 2002
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Scalability and
Performance
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Scalability and overhead of
communication vs. computation
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LU-based matrix inversion
Performance (send 32bit int matrix)
Full SOAP XML-encoded matrix
 SOAP Base64-encoded matrix
 CGI-based SOAP Web Service
 Stand-alone SOAP Web Service
 Java RMI
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IEEE CCGrid May 22, 2002
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Matrix Inversion
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IEEE CCGrid May 22, 2002
Stand-alone linear
system solver service
(TCP sockets)
Full double fp. matrix
representation in
SOAP XML
Total time of client
request and server
response (10BaseT,
Dual PIII 550MHz,
Red Hat Linux)
24
CGI-Based Web Service
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IEEE CCGrid May 22, 2002
Total time of client
request and server
response (10BaseT,
Dual PIII 550MHz,
Red Hat Linux)
SOAP XML-encoded
32bit int matrix
SOAP Base64encoded 32bit int
matrix
25
Stand-Alone Service
and Java RMI
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IEEE CCGrid May 22, 2002
Total time of client
request and server
response (10BaseT,
Dual PIII 550MHz,
Red Hat Linux)
SOAP XML-encoded
32bit int matrix
SOAP Base64encoded 32bit int
matrix
Java RMI (1.2.2)
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Conclusions
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Application centric
SOAP/XML Web Service interoperable
Legacy numerical code integration
Scalability and performance
Future work:
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IDL
DIME
Performance enhancements
Peer-to-peer networks
IEEE CCGrid May 22, 2002
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