1 karl 1.1.2.1 Using the CIM/XML Pull Operations
2
3 STATUS
4
5 <<< This section is being maintained during the review and checkin process
6 to keep track of problems, errors, notes, etc. Must be deleted before
7 checkin to head of tree. Please feel free to add notes, etc in this
8 section as you review/test.>>>>>>
9
10 16 Jan 2011
11
12 Issues - KS
13 1. have not installed the binary move in CIMResponseData. Please run
14 with OPP off.
15 2. Some problem in the processing so we are getting server crashes.
16 Right no I am guessing that this is in the binaryCodec and am going to
17 expand the test tools to allow testing through the localhost.
18
19 3. Still way to many TODO and KS comments and KS_TEMPS. Removing bit by bit.
20
21 4. Env variable connection for the config parameters not installed.
22 karl 1.1.2.1
23 5. Issue with the threaded timer. For some reason during tests it
24 eventually calls the timer thread with trash for the parm (which is
25 pointer to the EnumerationTable object). Caught because we do a valid
26 test at beginning of the function.
27
28 ===========================================
29
30 OVERVIEW:
31
32 The operation extensions for pull operations defined in the DMTF specification
33 DSP0200 V 1.4 were implemented in Pegasus effective Pegasus version 2.11
34 including Client and Server.
35
36 These operations extend the CIM/XML individual operations to operation
37 sequences where the server must maintain state between operations in a
38 sequence and the client must execute multiple operations to get the full
39 set of instances or instance paths.
40
41 The following new CIM/XML operations as defined in DSP0200 are included;
42
43 karl 1.1.2.1 -OpenEnumerateInstances
44 -openEnumerateInstancePaths
45 -OpenReferenceInstances
46 -OpenReferenceInstancePaths
47 -OpenAssociatiorInstances
48 -OpenAssociatorInstancePaths
49 -PullInstancesWithPath
50 -PullInstancePaths
51 -CloseEnumeration
52 -EnumerationCount
53
54 The following operations have not been implemented in this version of Pegasus:
55
56 -OpenQueryInstances
57
58 The following limitations on the implementation exist;
59
60 1. The filterQueryLanguage and filterQuery parameters are processed by
61 the Pegasus client but the server returns error if there is any data in
62 either parameter. This is because the definition of query language has not
63 been clarified to date by the DMTF.
64 karl 1.1.2.1
65 2. The input parameter continueOnError is processed correctly by the client
66 but the Pegasus server only provides for false since the server does not
67 include logic to continue processing responses after an error is
68 encountered.
69 This is consistent with the statement in the specification that use of
70 this functionality is optional and the fact that the DMTF agrees that all
71 of the issues of continuing after errors have not been clarified.
72
73 3. The operation enumerationCount is not processed by the server today since
74 a) really getting the count would be the same cost as the corresponding
75 enumeration, b) the server does not include a history or estimating
76 mechanism for this to date.
77 KS_TBD_ confirm this
78
79 Since the concept of sequences of operations linked together (open, pull, close)
80 is a major extension to the original CIM/XML operation concept of completely
81 independent operations several new pieces of functionality are implemented
82 to control interOperationTimeouts, counts of objects to be returned, etc.
83
84 TBD - Review this
85 karl 1.1.2.1
86 CLIENT
87
88 The new operations follow the same pattern as the APIs for existing operations
89 in that:
90
91 1. All errors are handled as CIMException and Exception
92
93 2. The means of inputting parameters are the same except that there are
94 significantly more input parameters with the open operations and for the
95 first time operations return parameters as well as objects in the
96 response. Specifically the open and pull operations return values for
97 enumerationContext which is the identity for a pull sequence and
98 endOfSequence which is the marker the server sends in open and pull
99 responses when it has no more objects to send.
100
101 The significant differences include:
102
103 1. Processing of parameters on responses (i.e. the endOfSequence and
104 enumerationContext parameters are returned for open and pull operations).
105
106 karl 1.1.2.1 2. Numeric arguments (Uint32 and Uint64 include the option of NULL in some
107 cases so they are packaged inside classes Uint32Arg and Uint64Arg in the
108 client api.
109
110 3. The association and reference operations ONLY process instances. They do
111 not include the capability to return classes like reference and associator
112 do and therefore return CIMInstance rather than CIMObject.
113
114 4. Paths are returned in all cases (i.e OpenEnumerateInstances and
115 PullInstancesWithPath where they were not with EnumeratInstances.
116
117 5. The client must maintain state between operations in a sequence (using
118 the enumerationContext parameter).
119
120 TBD- Are there more differences.
121
122
123 SERVER
124
125 The Pegasus server attempts to always deliver the requested number of objects
126 for any open or pull request (the specification allows for the server to
127 karl 1.1.2.1 deliver less than the requested number of objects and specifically to return
128 zero objects on open). We felt that it was worth any extra cost in processing
129 to provide the client with exactly what it had requested.
130
131 continueOnError Parameter
132 The pegasus server always closes an enumeration sequence upon receipt of any
133 error from the providers, repository, etc. Therefore the server will reject
134 and request that has continueOnError = true;
135
136 PROVIDERS
137
138 This implementation requires NO changes to the existing providers. The
139 provider APIs operate just as they do with the original operations.
140
141 Because the server processing is different however, there may be some
142 behavior differences primarily because the client now controls the speed of
143 delivery of objects.
144
145 In previous versions of Pegasus, the server attempts to deliver objects as
146 rapidly as then can be put on the network. In the case of HTTP chunked requests
147 they are delivered in chunks of about 100 objects. The primary delay for the
148 karl 1.1.2.1 providers was the processing of each segment through the server. The server
149 is blocked so that no other segment can proceed through the server until that
150 segment is processed and sent on the network.
151 In the case of non-chunkedresponses, they are completely gathered in the serve
152 and then delivered as one non-chunked response. There were no delays for the
153 providers, just lots of possible memory use in the server.
154
155 The responses from providers (delivered through the deliver(...) interface are
156 gathered into segments of about 100 objects and this group of objects is moved
157 through the server to be delivered to the client.
158
159 However with the inclusion of the pull operations, The segments of objects
160 from the providers are cached in the server response path until the
161 maxObjectCount for that request (open or pull) and that number returned in a
162 non-chunked response. Thus, if the client is slow to issue pull requests,
163 the providers might be delayed at some point to reduce memory usage in the
164 server (the delay appears as slow response tothe deliver operation).
165
166 In other words, the time to process large sets of responses from the provider
167 now depends on the speed of handling the client.
168
169 karl 1.1.2.1 It is important to remember in developing providers that the Pegasus server
170 can most efficiently process responses if they are passed from the provider
171 to the server individually or in small arrays of objects rather than the
172 provider gathering very large arrays of objects and sending them to the
173 server.
174
175 CONFIGURATION PARAMETERS
176
177 The server includes several configuration parameters to set limits on the
178 processing of pull operations. All of these configuration parameters are
179 compile time parameters rather than runtime.
180
181 1. Maximum value of minimum interoperation time. This parameter defines the
182 maximum time allowed between the return of an open or pull response and
183 the receipt of the next pull or a close operation before the server may
184 close the enumeration. The specification allows the server to set a
185 maximum interoperation time and refuse open requests that with requested
186 operationTimeout greater than that time.
187 CIM_ERR_INVALID_OPERATION_TIMEOUT
188
189 This value is set with the Pegasus environment variable
190 karl 1.1.2.1 PEGASUS_PULL....
191
192 2. Maximum objects returned in a single open or pull operation. The server
193 can set a maximum limit on the number of objects that can be returned in
194 a single open or pull oepration with the maxObjectCount parameter.
195
196 3. Whether the server allows 0 as an interoperation timeout value. The value
197 zero is s special value for the interoperationTimeout in that it tells the
198 server to not timeout any enumeration sequence.
199
200 With this value for interoperationTimeout, the only way to close an
201 enumeration sequence is to complete all of the pulls or issue the close.
202 If for some reason the sequence is not completed, that enumeration context
203 would remain open indefinitly. Since in Pegasus any open enumeration
204 context uses resources (the context object and any provider resposnes that
205 have not yet been issued in a response) it would appear that most
206 platforms would not want to allow the existence of enumeration contexts
207 that cannot be closed by the server.
208
209 4, maximum consecutive pull requests with 0 maxObjectCount. The use of the
210 pull operation with maxObjectCount set to zero could be used to keep an
211 karl 1.1.2.1 enumeration context open indefinitly (this tells the server to restart the
212 interoperationTimeout but not send any objects in the response). Therefore the
213 specification allows for the server setting maximum limits on this behavior
214 and returning the error CIM_ERR_SERVER_LIMITS_EXCEEDED if this limit is
215 exceeded.
216 Note that this is maximum CONSECUTIVE pulls so that issuing a pull with
217 a non-zero count resets this counter.
218
219 KS-TBD - Is this really logical since we can still block by just issuing
220 lots of zero request and an occansional request for one object.
221
222 Pegaus sets the value of this limit to 1000 and allows the implementer to
223 modify it with the PEGASUS_MAXIMUM_ZERO_OBJECTCOUNT environment variable.
224
225 5. Default operationTimeout -
226
227 The default of this parameter is to refuse operat
228
229 In the current release of Pegasus these are all compile time parameters.
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