Understanding Searching Timeouts

Timeouts affect whether our searches will finish completely or return partial results. In addition to the limits imposed by the server, the client has the ability to request specific timeout behaviors as well.

Precedence of Timeouts

Within the DirectorySearcher class are a number of members that represent a timeout value of some type or another. It can often be confusing to determine exactly when each timeout value is used and what precedence each has. In this section, we will hopefully dispel some of that confusion.

Let's start by examining the available timeout settings:

  • ClientTimeout
  • ServerPageTimeLimit
  • ServerTimeLimit

ClientTimeout

This TimeSpan represents the maximum amount of time that the client will wait for the server to return results before abandoning the search and returning no results. By default in SDS, this is set to wait indefinitely. If a TimeSpan greater than zero is provided, the client will wait the minimum of this value, or until an administrative server timeout is generated. Clients should set this to a reasonable value when expecting particularly long searches.

ServerPageTimeLimit

When used in conjunction with a paged search (see the section Returning Many Results with Paged Searches, in Chapter 4), this TimeSpan represents the maximum amount of time that the server should spend generating search results for a particular search page, before returning it to the client. As such, it is used only when searching for large result sets greater than the MaxPageSize that use paging (usually 1,000 results). Values greater than the MaxQueryDuration will essentially be ignored, as that will become the limiting factor per page. By default, this is set to wait indefinitely, so this means that in practice, the MaxQueryDuration will be used.

ServerTimeLimit

This TimeSpan specifies the maximum amount of time that the server will wait for a search to complete. If this value is exceeded, only the results accumulated to that point will be returned. By default, SDS is set to wait indefinitely. In practice, the limiting factor is the server's administrative LDAP search time limit of 120 seconds (MaxQueryDuration). All nonpaged searches must complete before the minimum of the ServerTimeLimit or MaxQueryDuration (the default is 120 seconds), or only the results accumulated to that point will be returned. Paged searches are not affected by this value.

Nonpaged Searches

When using a nonpaged search (i.e., PageSize equals zero), there are only three arbitrators of when a search will end. Table 5.2 summarizes these settings in a concise format.

Table 5.2. Nonpaged Timeout Precedence

Timeout Operator

Default Value

Precedence

Notes

MaxQueryDuration

120 seconds

First

This is an administrative limit found on the LDAPAdminLimit attribute. It is the maximum time any nonpaged search will be executed before the server generates a timeout. While it can be changed, it is not advisable to change this value from the default.

ServerTimeLimit

Indefinite

Second

Values larger than MaxQueryDuration will essentially be ignored, since the MaxQuery-Duration will be the limiting factor.

ClientTimeout

Indefinite

Third

The ServerTimeLimit takes precedence over this setting, so any value specified larger than the ServerTimeLimit will essentially be ignored.

 

Paged Searches

For a paged search (i.e., PageSize is greater than zero), there are again three arbitrators of when a search will end. Table 5.3 summarizes these settings.

Table 5.3. Paged Search Timeout Precedence

Timeout Operator

Default Value

Precedence

Notes

ServerPageTimeLimit

Indefinite

First

The ServerPageTimeLimit controls how much time the server will spend collecting an individual page. It does not control how long the entire search will last. A paged search will continue for as long as there are result pages, until it is finished.

ClientTimeout

Indefinite

Second

During a particularly long paged search, the client has the option of abandoning it using this timeout.

MaxQueryDuration

120 seconds

Third

This limit does not come into effect in practice very often, because this limit is applied per page and not per search.


Optimizing Search Performance

Part I: Fundamentals

Introduction to LDAP and Active Directory

Introduction to .NET Directory Services Programming

Binding and CRUD Operations with DirectoryEntry

Searching with the DirectorySearcher

Advanced LDAP Searches

Reading and Writing LDAP Attributes

Active Directory and ADAM Schema

Security in Directory Services Programming

Introduction to the ActiveDirectory Namespace

Part II: Practical Applications

User Management

Group Management

Authentication

Part III: Appendixes

Appendix A. Three Approaches to COM Interop with ADSI

Appendix B. LDAP Tools for Programmers

Appendix C. Troubleshooting and Help

Index



The. NET Developer's Guide to Directory Services Programming
The .NET Developers Guide to Directory Services Programming
ISBN: 0321350170
EAN: 2147483647
Year: 2004
Pages: 165

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