All varnish versions from 4. 2017-08-the varnish book pdf – Security releases: 4.
Varnish was designed as an HTTP accelerator. 10,000 sites in the web used the software. The support, management and development of Varnish was later spun off into a separate company, Varnish Software. Commercial support is available from Varnish Software, amongst others. This helps avoid the situation where the operating system starts caching data while it is moved to disk by the application. Most policy decisions are left to VCL code, making Varnish more configurable and adaptable than most other HTTP accelerators. A number of run-time parameters control things such as the maximum and minimum number of worker threads, various timeouts, etc.
A command-line management interface allows these parameters to be modified, and new VCL scripts to be compiled, loaded and activated, without restarting the accelerator. Varnish on Linux or Unix based environments. Varnish Cache can speed up information delivery by a factor of several hundred. Varnish Cache ships with monitoring and logging tools. One of the most used is varnishstat which gives a detailed snapshot of Varnish’s current performance.
It provides access to in-memory statistics such as cache hits and misses, resource consumption, threads created, and more. Running varnishstat from the command line returns a continuously updating list of all available Varnish metrics. If the -1 flag is added, varnishstat will exit after printing the list one time. Varnishstat can be used as a standalone tool to spot-check the health of the cache.
In order to graph metrics over time, correlate with other statistics from across an infrastructure, and set up alerts about any problems that may arise, monitoring services can integrate with Varnish and collect varnishstat metrics. Varnish’s configuration, as it provides detailed information about each individual request. Basic health-checking of backends is also available. Making Catalyst Sites Shine with Varnish”, Dec.
Re: Why is Windows 100 times slower than Linux when growing a large scalar? Varnish developer Poul-Henning Kamp describing the implementation of the LRU list. This page was last edited on 24 September 2017, at 18:26. The links below lead to . I will be adding more as each reaches a presentable state, if current permissions do not get misused.
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Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish. Resin varnishes “dry” by evaporation of the solvent and harden almost immediately upon drying. Oil, polyurethane, and epoxy varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to tacky or sticky, to dry gummy, to “dry to the touch”, to hard. Environmental factors such as heat and humidity play a very large role in the drying and curing times of varnishes.
In classic varnish the cure rate depends on the type of oil used and, to some extent, on the ratio of oil to resin. These are highly flammable in their liquid state. Thus, oil-soaked rags and paper can smolder and ignite into flames, even several hours after use if proper precautions are not taken. Early varnishes were developed by mixing resin—pine sap, for example—with a solvent and applying them with a brush to get the golden and hardened effect one sees in today’s varnishes. Libya, where the first varnishes in the Mediterranean area were used and where resins from the trees of now-vanished forests were sold.
As a result, these now antique pianos are considered difficult to refinish. However, shellac can be used over the existing resins provided sufficient time is allowed for thin coats to cure. Thus the original finish can be returned to its original lustre while preserving the color and age-related crackle. Touchup in repair or restoration is only done with spirit varnish. Traditionally the oil is prepared by cooking or exposure to air and sunlight, but modern “stand oil” is prepared by heating oil at high temperature without oxygen.
The refined resin is sometimes available as a translucent solid and is then “run” by cooking or literally melting it in a pot over heat without solvents. There is also evidence that finely powdered minerals, possibly volcanic ash, were used in some grounds. Some violins made in the late 18th century used oxen’s blood to create a very deep-red coloration. Today this varnish would have faded and currently be a very warm, dark orange. Some resins are soluble in both alcohol and turpentine. These were believed to impart special tonal qualities to musical instruments and thus were sometimes carefully guarded secrets.