add automatic self-healing when using slice plugin to t3c

CHANGELOG.md

@@ -53,6 +53,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - [#7652](https://github.com/apache/trafficcontrol/pull/7652) *Traffic Control Cache Config (t3c)*: added rpmdb checks and use package data from t3c-apply-metadata.json if rpmdb is corrupt.
 - [#7674](https://github.com/apache/trafficcontrol/issues/7674) *Traffic Ops*: Add the ability to indicate if a server failed its revalidate/config update.
 - [#7784](https://github.com/apache/trafficcontrol/pull/7784) *Traffic Portal*: Added revert certificate functionality to the ssl-keys page.
+- [#7719](https://github.com/apache/trafficcontrol/pull/7719) *t3c* self-healing will be added automatically when using the slice plugin.
 
 ### Changed
 - [#7776](https://github.com/apache/trafficcontrol/pull/7776) *tc-health-client*: Added error message while issues interacting with Traffic Ops.

docs/source/overview/delivery_services.rst

@@ -676,6 +676,8 @@ Describes how HTTP "Range Requests" should be handled by the Delivery Service at
 3
 	Use the `slice <https://github.com/apache/trafficserver/tree/master/plugins/experimental/slice>`_ plugin to slice range based requests into deterministic chunks. (Aliased as "3 - Use slice plugin" in Traffic Portal forms)
 
+	.. note:: The ``-–consider-ims`` parameter will automatically be added to the remap line by :term:`t3c` for self healing. If any other range request parameters are being used you must also include ``--consider-ims`` to enable self healing. Automatic self healing can be disabled by adding a remap.config parameter with a value of ``no_self_healing``
+
 		.. versionadded:: ATCv4.1
 
 .. note:: Range Request Handling can only be implemented on :term:`cache servers` using :abbr:`ATS (Apache Traffic Server)` because of its dependence on :abbr:`ATS (Apache Traffic Server)` plugins. The value may be set on any Delivery Service, but will have no effect when the :term:`cache servers` that ultimately end up serving the content are e.g. Grove, Nginx, etc.

lib/go-atscfg/remapdotconfig.go

@@ -71,6 +71,7 @@
 const DefaultFirstRemapConfigTemplateString = `map {{{Source}}} {{{Destination}}} {{{Strategy}}} {{{Dscp}}} {{{HeaderRewrite}}} {{{DropQstring}}} {{{Signing}}} {{{RegexRemap}}} {{{Cachekey}}} {{{RangeRequests}}} {{{Pacing}}} {{{RawText}}}`
 const DefaultLastRemapConfigTemplateString = `map {{{Source}}} {{{Destination}}} {{{Strategy}}} {{{HeaderRewrite}}} {{{Cachekey}}} {{{RangeRequests}}} {{{RawText}}}`
 const DefaultInnerRemapConfigTemplateString = DefaultLastRemapConfigTemplateString
+const selfHealParam = `no_self_healing`
 
 type LineTemplates map[string]*mustache.Template
 
@@ -223,23 +224,31 @@
 // This sticks the DS parameters in a map.
 // remap.config parameters use "<plugin>.pparam" key
 // cachekey.config parameters retain the 'cachekey.config' key.
-func classifyConfigParams(configParams []tc.ParameterV5) map[string][]tc.ParameterV5 {
+func classifyConfigParams(configParams []tc.ParameterV5) (map[string][]tc.ParameterV5, bool) {
 	configParamMap := map[string][]tc.ParameterV5{}
+	selfHeal := true
 	for _, param := range configParams {
 		key := param.ConfigFile
 		if "remap.config" == key {
 			key = param.Name
+			if param.Value == selfHealParam {
+				selfHeal = false
+				continue
+			}
 		}
 		configParamMap[key] = append(configParamMap[key], param)
 	}
-	return configParamMap
+	return configParamMap, selfHeal
 }
 
 // For general <plugin>.pparam parameters.
 func paramsStringFor(parameters []tc.ParameterV5, warnings *[]string) (paramsString string) {
 	uniquemap := map[string]int{}
 
 	for _, param := range parameters {
+		if strings.TrimSpace(param.Value) == "" {
+			continue
+		}
 		paramsString += " @pparam=" + param.Value
 
 		// Try to extract argument
@@ -407,9 +416,10 @@
 			cachekeyArgs = getQStringIgnoreRemap(atsMajorVersion)
 		}
 
+		selfHeal := true
 		dsConfigParamsMap := map[string][]tc.ParameterV5{}
 		if nil != ds.ProfileID {
-			dsConfigParamsMap = classifyConfigParams(profilesConfigParams[*ds.ProfileID])
+			dsConfigParamsMap, selfHeal = classifyConfigParams(profilesConfigParams[*ds.ProfileID])
 		}
 
 		if len(dsConfigParamsMap) > 0 {
@@ -421,8 +431,11 @@
 		}
 
 		if ds.RangeRequestHandling != nil && (*ds.RangeRequestHandling == tc.RangeRequestHandlingCacheRangeRequest || *ds.RangeRequestHandling == tc.RangeRequestHandlingSlice) {
-			remapTags.RangeRequests = `@plugin=cache_range_requests.so` +
-				paramsStringFor(dsConfigParamsMap["cache_range_requests.pparam"], &warnings)
+			crrParam := paramsStringFor(dsConfigParamsMap["cache_range_requests.pparam"], &warnings)
+			remapTags.RangeRequests = `@plugin=cache_range_requests.so` + crrParam
+			if *ds.RangeRequestHandling == tc.RangeRequestHandlingSlice && !strings.Contains(crrParam, "--consider-ims") && selfHeal {
+				remapTags.RangeRequests += ` @pparam=--consider-ims`
+			}
 		}
 
 		isLastCache, err := serverIsLastCacheForDS(server, &ds, nameTopologies, cacheGroups)
@@ -694,7 +707,7 @@
 		remapTags.HeaderRewrite = `@plugin=header_rewrite.so @pparam=` + edgeHeaderRewriteConfigFileName(ds.XMLID)
 	}
 
-	dsConfigParamsMap := classifyConfigParams(remapConfigParams)
+	dsConfigParamsMap, selfHeal := classifyConfigParams(remapConfigParams)
 
 	if ds.SigningAlgorithm != nil && *ds.SigningAlgorithm != "" {
 		if *ds.SigningAlgorithm == tc.SigningAlgorithmURLSig {
@@ -772,8 +785,10 @@
 		}
 
 		if crr {
-			rangeReqTxt += `@plugin=cache_range_requests.so ` +
-				paramsStringFor(dsConfigParamsMap["cache_range_requests.pparam"], &warnings)
+			rangeReqTxt += `@plugin=cache_range_requests.so ` + paramsStringFor(dsConfigParamsMap["cache_range_requests.pparam"], &warnings)
+			if *ds.RangeRequestHandling == tc.RangeRequestHandlingSlice && !strings.Contains(rangeReqTxt, "--consider-ims") && selfHeal {
+				rangeReqTxt += ` @pparam=--consider-ims`
+			}
 		}
 	}