[docs] (DebugPoints) Update docs about Debug Points

docs/en/docs/admin-manual/http-actions/fe/debug-point-action.md

@@ -26,18 +26,26 @@ under the License.
 
 # Debug Point
 
-Debug point is used in code test. When enabling a debug point, it can run related code.
+Debug point is a piece of code, inserted into FE or BE code, when program running into this code, 
 
-Both FE and BE support debug points.
+it can change variables or behaviors of the program. 
+
+It is mainly used for unit test or regression test when it is impossible to trigger some exceptions through normal means.
+
+Each debug point has a name, the name can be whatever you want, there are swithes to enable and disable debug points, 
+
+and you can also pass data to debug points.
+
+Both FE and BE support debug point, and after inserting debug point code, recompilation of FE or BE is needed.
 
 ## Code Example
 
 FE example
 
 ```java
 private Status foo() {
-	// dbug_fe_foo_do_nothing is the debug point name.
-	// When it's active，DebugPointUtil.isEnable("dbug_fe_foo_do_nothing") will return true.
+	// dbug_fe_foo_do_nothing is the debug point name
+	// when it's active, DebugPointUtil.isEnable("dbug_fe_foo_do_nothing") returns true
 	if (DebugPointUtil.isEnable("dbug_fe_foo_do_nothing")) {
       	return Status.Nothing;
     }
@@ -48,46 +56,50 @@ private Status foo() {
 }
 ```
 
-BE 桩子示例代码
+BE example
 
 ```c++
 void Status foo() {
-     // dbug_be_foo_do_nothing is the debug point name.
-     // When it's active，DEBUG_EXECUTE_IF will execute the code block.
-     DEBUG_EXECUTE_IF("dbug_be_foo_do_nothing",  { return Status.Nothing; });
+     // dbug_be_foo_do_nothing is the debug point name
+     // when it's active, DBUG_EXECUTE_IF will execute the code block
+     DBUG_EXECUTE_IF("dbug_be_foo_do_nothing",  { return Status.Nothing; });
 
      do_foo_action();
 
      return Status.Ok;
 }
 ```
 
-## Global config
 
-To activate debug points, need set `enable_debug_points` to true.
+## Global Config
+
+To enable debug points globally, we need to set `enable_debug_points` to true,
+
+`enable_debug_points` is located in FE's fe.conf and BE's be.conf.
 
-`enable_debug_points` was located in FE's fe.conf and BE's be.conf。
 
+## Activate A Specified Debug Point
 
-## Enable Debug Point
+After debug points are enabled globally, a http request with a debug point name should be send to FE or BE node, <br/>
+only after that, when the program running into the specified debug point, related code can be executed.
 
 ### API
 
 ```
-	POST /api/debug_point/add/{debug_point_name}[?timeout=<int>&execute=<int>]
+POST /api/debug_point/add/{debug_point_name}[?timeout=<int>&execute=<int>]
 ```
 
 
 ### Query Parameters
 
 * `debug_point_name`
-    Debug point name. Require.
+    Debug point name. Required.
 
 * `timeout`
-    Timeout in seconds. When timeout, the debug point will be disable. Default is -1,  not timeout. Optional.
+    Timeout in seconds. When timeout, the debug point will be deactivated. Default is -1, never timeout. Optional.
 
 * `execute`
-    Max active times。Default is -1,  unlimit active times. Optional.  
+    After activating, the max times the debug point can be executed. Default is -1,  unlimited times. Optional.  
 
 
 ### Request body
@@ -96,24 +108,105 @@ None
 
 ### Response
 
-    ```
-    {
-        msg: "OK",
-        code: 0
-    }
-    ```
+```
+{
+    msg: "OK",
+    code: 0
+}
+```
 
 ### Examples
 
 
-Enable debug point `foo`, activate no more than five times.
+After activating debug point `foo`, executed no more than five times.
 
 
-    ```
-    curl -X POST "http://127.0.0.1:8030/api/debug_point/add/foo?execute=5"
+```
+curl -X POST "http://127.0.0.1:8030/api/debug_point/add/foo?execute=5"
+
+```
+
+
+## Pass Custom Parameters
+When activating debug point, besides "timeout" and "execute" mentioned above, passing custom parameters is also allowed.<br/>
+A parameter is a key-value pair in the form of "key=value" in url path, after debug point name glued by charactor '?'.<br/> 
+See examples below.
+
+### API
+
+```
+POST /api/debug_point/add/{debug_point_name}[?k1=v1&k2=v2&k3=v3...]
+```
+* `k1=v1` <br/>
+  k1 is parameter name <br/>
+  v1 is parameter value <br/>
+  multiple key-value pairs are concatenated by `&` <br/>
+
+
+
+### Request body
+
+None
+
+### Response
+
+```
+{
+    msg: "OK",
+    code: 0
+}
+```
+
+### Examples
+Assuming a FE node with configuration http_port=8030 in fe.conf, <br/>
+the following http request activates a debug point named `foo` in FE node and passe parameter `percent` and `duration`:
+>NOTE: User name and password may be needed.
+```
+curl -u root: -X POST "http://127.0.0.1:8030/api/debug_point/add/foo?percent=0.5&duration=3"
+```
+
+```
+NOTE:
+1. Inside FE and BE code, names and values of parameters are taken as strings.
+2. Parameter names and values are case sensitive in http request and FE/BE code.
+3. FE and BE share same url paths of REST API, it's just their IPs and Ports are different.
+```
+
+### Use parameters in FE and BE code
+Following request activates debug point `OlapTableSink.write_random_choose_sink` in FE and passes parameter `needCatchUp` and `sinkNum`: 
+```
+curl -u root: -X POST "http://127.0.0.1:8030/api/debug_point/add/OlapTableSink.write_random_choose_sink?needCatchUp=true&sinkNum=3"
+```
+
+The code in FE checks debug point `OlapTableSink.write_random_choose_sink` and gets parameter values:
+```java
+private void debugWriteRandomChooseSink(Tablet tablet, long version, Multimap<Long, Long> bePathsMap) {
+    DebugPoint debugPoint = DebugPointUtil.getDebugPoint("OlapTableSink.write_random_choose_sink");
+    if (debugPoint == null) {
+        return;
+    }
+    boolean needCatchup = debugPoint.param("needCatchUp", false);
+    int sinkNum = debugPoint.param("sinkNum", 0);
+    ...
+}
+```
+
+Following request activates debug point `TxnManager.prepare_txn.random_failed` in BE and passes parameter `percent`:
+```
+curl -X POST "http://127.0.0.1:8040/api/debug_point/add/TxnManager.prepare_txn.random_failed?percent=0.7
+```
+
+The code in BE checks debug point `TxnManager.prepare_txn.random_failed` and gets parameter value:
+```c++
+DBUG_EXECUTE_IF("TxnManager.prepare_txn.random_failed",
+		{if (rand() % 100 < (100 * dp->param("percent", 0.5))) {
+		        LOG_WARNING("TxnManager.prepare_txn.random_failed random failed");
+		        return Status::InternalError("debug prepare txn random failed");
+		}}
+);
+```
+
 
-    ```
-
 ## Disable Debug Point
 
 ### API
@@ -137,10 +230,10 @@ None
 ### Response
 
 ```
-    {
-        msg: "OK",
-        code: 0
-    }
+{
+    msg: "OK",
+    code: 0
+}
 ```
 
 ### Examples
@@ -149,17 +242,17 @@ None
 Disable debug point `foo`。
 
 
-    ```
-    curl -X POST "http://127.0.0.1:8030/api/debug_point/remove/foo"
+```
+curl -X POST "http://127.0.0.1:8030/api/debug_point/remove/foo"
 
-    ```
+```
 
 ## Clear Debug Points
 
 ### API
 
 ```
-	POST /api/debug_point/clear
+POST /api/debug_point/clear
 ```
 
 
@@ -170,16 +263,78 @@ None
 
 ### Response
 
-    ```
-    {
-        msg: "OK",
-        code: 0
-    }
-    ```
+```
+{
+    msg: "OK",
+    code: 0
+}
+```
 
 ### Examples
 
 
-    ```
-    curl -X POST "http://127.0.0.1:8030/api/debug_point/clear"
-    ```
+```
+curl -X POST "http://127.0.0.1:8030/api/debug_point/clear"
+```
+
+## Debug Points in Regression Test
+
+>In community's CI system, `enable_debug_points` configuration of FE and BE are true by default.
+
+The Regression test framework also provides methods to activate and deactivate a particular debug point, <br/>
+they are declared as below:
+```groovy
+// "name" is the debug point to activate, "params" is a list of key-value pairs passed to debug point
+def enableDebugPointForAllFEs(String name, Map<String, String> params = null);
+def enableDebugPointForAllBEs(String name, Map<String, String> params = null);
+// "name" is the debug point to deactivate
+def disableDebugPointForAllFEs(String name);
+def disableDebugPointForAllFEs(String name);
+```
+`enableDebugPointForAllFEs()` or `enableDebugPointForAllBEs()` needs to be called before the test actions you want to generate error, <br/>
+and `disableDebugPointForAllFEs()` or `disableDebugPointForAllBEs()` needs to be called afterward.
+
+### Concurrent Issue
+
+Enabled debug points affects FE or BE globally, which could cause other concurrent tests to fail unexpectly in your pull request. <br/>
+To avoid this, there's a convension that regression tests using debug points must be in directory regression-test/suites/fault_injection_p0, <br/>
+and their group name must be "nonConcurrent", as these regression tests will be executed serially by pull request workflow. 
+
+### Examples
+
+```groovy
+// .groovy file of the test case must be in regression-test/suites/fault_injection_p0
+// and the group name must be 'nonConcurrent'
+suite('debugpoint_action', 'nonConcurrent') {
+    try {
+        // Activate debug point named "PublishVersionDaemon.stop_publish" in all FE
+        // and pass parameter "timeout"
+        // "execute" and "timeout" are pre-existing parameters, usage is mentioned above
+        GetDebugPoint().enableDebugPointForAllFEs('PublishVersionDaemon.stop_publish', [timeout:1])
+
+        // Activate debug point named "Tablet.build_tablet_report_info.version_miss" in all BE
+        // and pass parameter "tablet_id", "version_miss" and "timeout"
+        GetDebugPoint().enableDebugPointForAllBEs('Tablet.build_tablet_report_info.version_miss',
+                                                  [tablet_id:'12345', version_miss:true, timeout:1])
+
+        // Test actions which will run into debug point and generate error
+        sql """CREATE TABLE tbl_1 (k1 INT, k2 INT)
+               DUPLICATE KEY (k1)
+               DISTRIBUTED BY HASH(k1)
+               BUCKETS 3
+               PROPERTIES ("replication_allocation" = "tag.location.default: 1");
+            """
+        sql "INSERT INTO tbl_1 VALUES (1, 10)"
+        sql "INSERT INTO tbl_1 VALUES (2, 20)"
+        order_qt_select_1_1 'SELECT * FROM tbl_1'
+
+    } finally {
+        // Deactivate debug points
+        GetDebugPoint().disableDebugPointForAllFEs('PublishVersionDaemon.stop_publish')
+        GetDebugPoint().disableDebugPointForAllBEs('Tablet.build_tablet_report_info.version_miss')
+    }
+}
+```
+
+
+