Line data    Source code

       1             : // Copyright (C) 2021 The Android Open Source Project
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.server.mail.send;
      16             : 
      17             : import static com.google.common.base.Preconditions.checkArgument;
      18             : 
      19             : import com.google.common.cache.CacheLoader;
      20             : import com.google.common.cache.LoadingCache;
      21             : import com.google.common.util.concurrent.ListenableFuture;
      22             : import com.google.common.util.concurrent.ListeningExecutorService;
      23             : import com.google.gerrit.server.CacheRefreshExecutor;
      24             : import com.google.gerrit.server.cache.CacheModule;
      25             : import com.google.inject.Inject;
      26             : import com.google.inject.ProvisionException;
      27             : import com.google.inject.Singleton;
      28             : import com.google.inject.name.Named;
      29             : import com.google.template.soy.jbcsrc.api.SoySauce;
      30             : import java.time.Duration;
      31             : import java.util.concurrent.ExecutionException;
      32             : import javax.inject.Provider;
      33             : 
      34             : /**
      35             :  * Provides support for soy templates
      36             :  *
      37             :  * <p>Module loads templates with {@link MailSoySauceLoader} and caches compiled templates. The
      38             :  * cache refreshes automatically, so Gerrit does not need to be restarted if templates are changed.
      39             :  */
      40         152 : public class MailSoySauceModule extends CacheModule {
      41             :   static final String CACHE_NAME = "soy_sauce_compiled_templates";
      42             :   private static final String SOY_LOADING_CACHE_KEY = "KEY";
      43             : 
      44             :   @Override
      45             :   protected void configure() {
      46             :     // Cache stores only a single key-value pair (key is SOY_LOADING_CACHE_KEY). We are using
      47             :     // cache only for it refresh/expire logic.
      48         152 :     cache(CACHE_NAME, String.class, SoySauce.class)
      49             :         // Cache refreshes a value only on the access (if refreshAfterWrite interval is
      50             :         // passed). While the value is refreshed, cache returns old value.
      51             :         // Adding expireAfterWrite interval prevents cache from returning very old template.
      52         152 :         .refreshAfterWrite(Duration.ofSeconds(5))
      53         152 :         .expireAfterWrite(Duration.ofMinutes(1))
      54         152 :         .loader(SoySauceCacheLoader.class);
      55         152 :     bind(SoySauce.class).annotatedWith(MailTemplates.class).toProvider(SoySauceProvider.class);
      56         152 :   }
      57             : 
      58             :   @Singleton
      59             :   static class SoySauceProvider implements Provider<SoySauce> {
      60             :     private final LoadingCache<String, SoySauce> templateCache;
      61             : 
      62             :     @Inject
      63         146 :     SoySauceProvider(@Named(CACHE_NAME) LoadingCache<String, SoySauce> templateCache) {
      64         146 :       this.templateCache = templateCache;
      65         146 :     }
      66             : 
      67             :     @Override
      68             :     public SoySauce get() {
      69             :       try {
      70         106 :         return templateCache.get(SOY_LOADING_CACHE_KEY);
      71           0 :       } catch (ExecutionException e) {
      72           0 :         throw new ProvisionException("Can't get SoySauce from the cache", e);
      73             :       }
      74             :     }
      75             :   }
      76             : 
      77             :   @Singleton
      78             :   static class SoySauceCacheLoader extends CacheLoader<String, SoySauce> {
      79             :     private final ListeningExecutorService executor;
      80             :     private final MailSoySauceLoader loader;
      81             : 
      82             :     @Inject
      83             :     SoySauceCacheLoader(
      84         152 :         @CacheRefreshExecutor ListeningExecutorService executor, MailSoySauceLoader loader) {
      85         152 :       this.executor = executor;
      86         152 :       this.loader = loader;
      87         152 :     }
      88             : 
      89             :     @Override
      90             :     public SoySauce load(String key) throws Exception {
      91         106 :       checkArgument(
      92         106 :           SOY_LOADING_CACHE_KEY.equals(key),
      93             :           "Cache can have only one element with a key '%s'",
      94             :           SOY_LOADING_CACHE_KEY);
      95         106 :       return loader.load();
      96             :     }
      97             : 
      98             :     @Override
      99             :     public ListenableFuture<SoySauce> reload(String key, SoySauce soySauce) {
     100          41 :       return executor.submit(() -> loader.load());
     101             :     }
     102             :   }
     103             : }