Script: Deprecate script context cache

docs/reference/migration/migrate_7_16.asciidoc

@@ -321,4 +321,30 @@ avoid deprecation warnings and opt into the future behaviour, include the query
 parameter `?return_200_for_cluster_health_timeout` in your request.
 ====
 
+[[script-context-cache-deprecated]]
+.The script context cache is deprecated
+[%collapsible]
+====
+*Details* +
+Setting `script.max_compilations_rate` to `use-context` and
+configuring context-specific caches is deprecated.
+
+Context-specific caches are no longer needed to prevent system scripts
+from triggering rate limits.
+
+Configure the general cache to control the max compilation rate, cache size, and
+cache expiration for your scripts.
+
+*Impact* +
+Remove `script.max_compilations_rate: use-context` and the context-specific cache
+settings: `script.context.$CONTEXT.cache_max_size`,
+`script.context.$CONTEXT.max_compilations_rate`, `script.context.$CONTEXT.cache_expire`.
+
+The general cache defaults to a max size of 3000 with a rate limit of 150/5m,
+which allows 150 compilations per 5 minute period.  By default, the entries in the
+cache do not expire.
+
+To override the defaults, configure the `script.cache.max_size`,
+`script.max_compilations_rate`, and `script.cache.expire` settings.
+====
 // end::notable-breaking-changes[]

docs/reference/modules/indices/circuit_breaker.asciidoc

@@ -126,11 +126,11 @@ within a period of time.
 See the "prefer-parameters" section of the <<modules-scripting-using,scripting>>
 documentation for more information.
 
-`script.context.$CONTEXT.max_compilations_rate`::
+`script.max_compilations_rate`::
     (<<dynamic-cluster-setting,Dynamic>>)
     Limit for the number of unique dynamic scripts within a certain interval
-    that are allowed to be compiled for a given context. Defaults to `75/5m`,
-    meaning 75 every 5 minutes.
+    that are allowed to be compiled. Defaults to `150/5m`,
+    meaning 150 every 5 minutes.
 
 [[regex-circuit-breaker]]
 [discrete]

docs/reference/scripting/using.asciidoc

@@ -120,12 +120,8 @@ the `multiplier` parameter without {es} recompiling the script.
 }
 ----
 
-For most contexts, you can compile up to 75 scripts per 5 minutes by default.
-For ingest contexts, the default script compilation rate is unlimited. You
-can change these settings dynamically by setting
-`script.context.$CONTEXT.max_compilations_rate`. For example, the following
-setting limits script compilation to 100 scripts every 10 minutes for the
-{painless}/painless-field-context.html[field context]:
+You can compile up to 150 scripts per 5 minutes by default.
+For ingest contexts, the default script compilation rate is unlimited.
 
 [source,js]
 ----
@@ -406,8 +402,8 @@ small.
 
 All scripts are cached by default so that they only need to be recompiled
 when updates occur. By default, scripts do not have a time-based expiration.
-You can change this behavior by using the `script.context.$CONTEXT.cache_expire` setting.
-Use the `script.context.$CONTEXT.cache_max_size` setting to configure the size of the cache.
+You can change this behavior by using the `script.cache.expire` setting.
+Use the `script.cache.max_size` setting to configure the size of the cache.
 
 NOTE: The size of scripts is limited to 65,535 bytes. Set the value of `script.max_size_in_bytes` to increase that soft limit. If your scripts are
 really large, then consider using a

server/src/main/java/org/elasticsearch/script/ScriptService.java

@@ -23,6 +23,8 @@
 import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.logging.DeprecationCategory;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
@@ -50,6 +52,7 @@
 public class ScriptService implements Closeable, ClusterStateApplier, ScriptCompiler {
 
     private static final Logger logger = LogManager.getLogger(ScriptService.class);
+    private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(ScriptService.class);
 
     static final String DISABLE_DYNAMIC_SCRIPTING_SETTING = "script.disable_dynamic";
 
@@ -59,16 +62,22 @@ public class ScriptService implements Closeable, ClusterStateApplier, ScriptComp
     static final String USE_CONTEXT_RATE_KEY = "use-context";
 
     public static final Setting<Integer> SCRIPT_GENERAL_CACHE_SIZE_SETTING =
-        Setting.intSetting("script.cache.max_size", 100, 0, Property.NodeScope);
+        Setting.intSetting("script.cache.max_size", 3000, 0, Property.Dynamic, Property.NodeScope);
     public static final Setting<TimeValue> SCRIPT_GENERAL_CACHE_EXPIRE_SETTING =
-        Setting.positiveTimeSetting("script.cache.expire", TimeValue.timeValueMillis(0), Property.NodeScope);
+        Setting.positiveTimeSetting("script.cache.expire", TimeValue.timeValueMillis(0), Property.Dynamic, Property.NodeScope);
     public static final Setting<Integer> SCRIPT_MAX_SIZE_IN_BYTES =
         Setting.intSetting("script.max_size_in_bytes", 65535, 0, Property.Dynamic, Property.NodeScope);
     public static final Setting<ScriptCache.CompilationRate> SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING =
-        new Setting<>("script.max_compilations_rate", USE_CONTEXT_RATE_KEY,
+        new Setting<>("script.max_compilations_rate", "150/5m",
             (String value) -> value.equals(USE_CONTEXT_RATE_KEY) ? USE_CONTEXT_RATE_VALUE: new ScriptCache.CompilationRate(value),
             Property.Dynamic, Property.NodeScope);
 
+    public static final String USE_CONTEXT_RATE_KEY_DEPRECATION_MESSAGE = "[" + USE_CONTEXT_RATE_KEY + "] is deprecated for the setting [" +
+        SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.getKey() + "] as system scripts are now exempt from the rate limit. " +
+        "Set to a value such as [150/5m] (a rate of 150 compilations per five minutes) to rate limit user scripts in case the " +
+        "script cache [" + SCRIPT_GENERAL_CACHE_SIZE_SETTING.getKey() + "] is undersized causing script compilation thrashing.";
+
+
     // Per-context settings
     static final String CONTEXT_PREFIX = "script.context.";
 
@@ -77,13 +86,14 @@ public class ScriptService implements Closeable, ClusterStateApplier, ScriptComp
     public static final Setting.AffixSetting<Integer> SCRIPT_CACHE_SIZE_SETTING =
         Setting.affixKeySetting(CONTEXT_PREFIX,
             "cache_max_size",
-            key -> Setting.intSetting(key, SCRIPT_GENERAL_CACHE_SIZE_SETTING, 0, Property.NodeScope, Property.Dynamic));
+            key -> Setting.intSetting(key, SCRIPT_GENERAL_CACHE_SIZE_SETTING, 0,
+                                      Property.NodeScope, Property.Dynamic, Property.Deprecated));
 
     public static final Setting.AffixSetting<TimeValue> SCRIPT_CACHE_EXPIRE_SETTING =
         Setting.affixKeySetting(CONTEXT_PREFIX,
             "cache_expire",
             key -> Setting.positiveTimeSetting(key, SCRIPT_GENERAL_CACHE_EXPIRE_SETTING, TimeValue.timeValueMillis(0),
-                                               Property.NodeScope, Property.Dynamic));
+                                               Property.NodeScope, Property.Dynamic, Property.Deprecated));
 
     // Unlimited compilation rate for context-specific script caches
     static final String UNLIMITED_COMPILATION_RATE_KEY = "unlimited";
@@ -94,7 +104,7 @@ public class ScriptService implements Closeable, ClusterStateApplier, ScriptComp
             key -> new Setting<ScriptCache.CompilationRate>(key, "75/5m",
                 (String value) -> value.equals(UNLIMITED_COMPILATION_RATE_KEY) ? ScriptCache.UNLIMITED_COMPILATION_RATE:
                                                                                  new ScriptCache.CompilationRate(value),
-                Property.NodeScope, Property.Dynamic));
+                Property.NodeScope, Property.Dynamic, Property.Deprecated));
 
     private static final ScriptCache.CompilationRate SCRIPT_COMPILATION_RATE_ZERO = new ScriptCache.CompilationRate(0, TimeValue.ZERO);
 
@@ -205,6 +215,10 @@ public ScriptService(Settings settings, Map<String, ScriptEngine> engines, Map<S
         this.setCacheHolder(settings);
     }
 
+    public static boolean isUseContextCacheSet(Settings settings) {
+        return SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.get(settings).equals(USE_CONTEXT_RATE_VALUE);
+    }
+
     /**
      * This is overridden in tests to disable compilation rate limiting.
      */
@@ -249,6 +263,10 @@ void registerClusterSettingsListeners(ClusterSettings clusterSettings) {
      */
     void validateCacheSettings(Settings settings) {
         boolean useContext = SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.get(settings).equals(USE_CONTEXT_RATE_VALUE);
+        if (useContext) {
+            deprecationLogger.warn(DeprecationCategory.SCRIPTING, "scripting-context-cache",
+                    USE_CONTEXT_RATE_KEY_DEPRECATION_MESSAGE);
+        }
         List<Setting.AffixSetting<?>> affixes = Arrays.asList(SCRIPT_MAX_COMPILATIONS_RATE_SETTING, SCRIPT_CACHE_EXPIRE_SETTING,
                                                               SCRIPT_CACHE_SIZE_SETTING);
         List<String> customRates = new ArrayList<>();
@@ -277,7 +295,7 @@ void validateCacheSettings(Settings settings) {
                     String.join(", ", customRates) + "] if compile rates disabled via [" +
                     SCRIPT_DISABLE_MAX_COMPILATIONS_RATE_SETTING.getKey() + "]");
             }
-            if (useContext == false) {
+            if (useContext == false && SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.exists(settings)) {
                 throw new IllegalArgumentException("Cannot set custom general compilation rates [" +
                     SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.getKey() + "] to [" +
                     SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.get(settings) + "] if compile rates disabled via [" +
@@ -568,6 +586,7 @@ void setCacheHolder(Settings settings) {
         } else if (current.general.rate.equals(SCRIPT_GENERAL_MAX_COMPILATIONS_RATE_SETTING.get(settings)) == false ||
                    current.general.cacheExpire.equals(SCRIPT_GENERAL_CACHE_EXPIRE_SETTING.get(settings)) == false ||
                    current.general.cacheSize != SCRIPT_GENERAL_CACHE_SIZE_SETTING.get(settings)) {
+            // General compilation rate, cache expiration or cache size changed
             cacheHolder.set(generalCacheHolder(settings));
         }
     }