- Enhance rule checking in rule managers and Sentinel Dashboard frontend
- Enhance error information when reporting invalid fields in rule dialog

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Enhance resolve name logic in MethodUtil
- Add test case for MethodUtil

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Change log file name;
- Add configurability to log file name and metric file name.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

* sentinel-transport-netty-http will also retry when port specified has been used
* LogBase support variable arguments
* Remove duplicated JVM properties overriding in SentinelConfig
* Add VersionUtil to get version from jar

* Add a new DegradeRule type, degrade by exception count in the last 60 seconds
* Add demo about degrading by exception count

normalize metric fields and methods:
- rename exception to exceptionQps;
- remove ed postfix of all fields and methods about metrics;

Signed-off-by: Carpenter Lee <hooleeucas@163.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Add callback registry for statistic slot for extensions.
- Add a new module `sentinel-parameter-flow-control` under `sentinel-extension`.
- Add a `CacheMap` interface to provide abstraction for cache. We use ConcurrentLinkedHashMap as the default implementation (LRU strategy)..
- Add a `ParameterMetric` class as frequent parameter metrics for a specific resource. The metric map is located in `ParamFlowSlot` rather than `ClusterNode`.
- Implement `ParameterLeapArray` as statistic data structure for frequent parameters in a period of time window.
- Add `ParamFlowSlot` as the checker slot; Add `ParamFlowChecker` to do rule checking; Add `ParamFlowRuleManager` to do rule managing.
- The statistic metrics for frequent parameters is enabled only if the related resource has configured parameter flow rule; Parameter metrics for removed rules will be cleared automatically.
- Leverage extensible `SlotChainBuilder` to provide a `HotParamSlotChainBuilder`.
- Add command handlers for hot param rules.
- Add test cases and demo.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- When amount of context exceeds the threshold, the `NullContext` will be set to current thread local. Thus, when checking context in `CtSph#entry`, once `NullContext` detected, the entry will not do rule checking on the slot chain.
- Cache the default context during initialization. Then when amount of context exceeds the threshold, entries under default context can do rule checking under default context.
- Enhance the error message

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

2. Add more java doc for LeapArray.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Support extensible `SlotChainBuilder` using SPI mechanism
- Add a `SlotChainProvider` to load slot chain builder and create new slot chains

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Some refinement for file data source
- Add resource name checking in FlowRuleManager to avoid NPE

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Fix incorrect usage. It's not thread-safe when comparing and updating `minRt`, but it's okay since the actual minimum RT often matches free load.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Comment/javadoc refinement

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- This bug can cause init failure of `AppNameUtil`

Signed-off-by: Eric Zhao <sczyh16@gmail.com>