HTTP Cache

The HTTP Cache in WinGate provides caching for HTTP requests made via an HTTP proxy.

Caching saves Internet bandwidth and provides faster client responses by serving requests from disk when possible instead of retrieving content from a remote web server. Responses to user requests are stored in the cache for future use. When the same request is made by another user it may be served from disk at LAN speed, thereby saving time and bandwidth. If you have many users accessing the same web sites then caching can provide significant performance improvements.

The HTTP Cache has been designed to be HTTP/1.1 compliant. This means it is compatible with the cache extensions and the control features specified in HTTP/1.1, including negotiated content, expiry and ageing, revalidation and content encoding.

Multiple cache volumes (WinGate Enterprise licenses only)

In general, a cache's value increases as it gets bigger. The more files stored, the higher the likelihood that any particular future request will be able to be served from cache, and therefore the higher the likelihood that the cache will save time and bandwidth for any given request.

This means in general a cache should be allowed to grow as big as possible.

Storing a lot of files on disk poses several problems, including file system performance issues and capacity. WinGate's HTTP cache addresses these problems by providing the capability to use multiple cache volumes.

For each volume, you specify the location and the maximum disk space the volume may use. As files are added to a volume, sub-folders are created as necessary to limit the number of files placed in any one folder. This keeps file system directory table sizes manageable and prevents degradation of file access times which can have a significant negative impact on cache performance.

Cache volumes should be on different physical disks. It provides no benefit to have more than one volume on the same physical disk.

Volumes can be created and deleted at any time. This allows the system to scale to large cache sizes.

Cache index

Caches require an index to keep track of all the files in the cache. The index allows the HTTP Cache to quickly look up which file is the result of a previous request so it can be served, and to store information for subsequent requests.

WinGate 8

In WinGate 8 the cache index is implemented with a proprietary indexing system and not a database. This provides improved performance and reliability over the previous WinGate 7 database index.

If a cache volume becomes unavailable (The computer housing a UNC based cache volume goes down) then that volume goes offline. The volume will return to the online status when access to the volume is restored.

WinGate 7

In WinGate 7, this cache index is stored in an ODBC-compatible database. ODBC is a standard database interface supported by many database vendors, including all the major ones.

Using ODBC provides several benefits:

You have a choice of database to use, and can use an existing one you are familiar with.
The data is accessible to external programs, and can be used to generate reports on cache usage, and to mark records for deletion outside of WinGate.
Many mature enterprise database systems are highly scalable and very high performance. This allows WinGate to store a large number of files in cache.
In future, using client-server databases, it will be possible for multiple WinGate installations to share the same cache index, thereby creating a cache farm.

The HTTP Cache panel

Management of the cache is performed using the HTTP Cache panel in the WinGate Management console. The HTTP Cache panel shows realtime volume usage, and cache performance statistics. You can also configure cache settings, manage (pause, restart, empty, delete, create) volumes, manage purging, and choose a database to use.

HTTP Cache rules

NOTE: WinGate 8 only

WinGate 8 introduces the concept of cahe rules. These rules allow you to control what resources are cached, forcing caching if you wish, and for how long. The rules can be configured to match on the source site and/or Content-Type of the resource.

Extensions to other WinGate systems

The HTTP Cache registers a custom policy item with the WinGate Policy system. This allows you to control on a per-request basis whether a client request may be served from cache or added to the cache. This allows you to control (among other things) which sites may be cached, or retrieved from cache.

The HTTP Cache also registers several control points with the WinGate Data system. This allows control of certain cache functions from switches on a dashboard.

The HTTP Cache also registers several data values with the WinGate Data system for data monitoring. These values allow WinGate to monitor aspects of the cache's state, such as its size, number of files, number of bytes transferred through the cache, and served from cache.

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