diff --git a/docs/devGuide/writingPlugins.md b/docs/devGuide/writingPlugins.md
index dab6b367b4..2654abaf53 100644
--- a/docs/devGuide/writingPlugins.md
+++ b/docs/devGuide/writingPlugins.md
@@ -169,3 +169,12 @@ removing such potential conflicts.
 Note however, that variable interpolation syntax {% raw %}`{{ variable_name }}`{% endraw %} will act as per normal.
 Meaning, the user would still be able to use variables in your special tags!
 </box>
+
+## Lifecycle hooks
+
+You may also need to maintain some plugin state during site generation, then reset this when the site or pages are regenerated.
+
+To do this, you may implement the `beforeSiteGenerate` method.
+
+- `beforeSiteGenerate()`: Called during initial site generation and subsequent regenerations during live preview.
+  - No return value is required.
diff --git a/packages/core/src/Site/index.js b/packages/core/src/Site/index.js
index 459af58588..f61a50b2e3 100644
--- a/packages/core/src/Site/index.js
+++ b/packages/core/src/Site/index.js
@@ -137,6 +137,7 @@ class Site {
     this.baseUrlMap = new Set();
     this.forceReload = forceReload;
     this.plugins = {};
+    this.pluginsBeforeSiteGenerate = [];
     /**
      * @type {undefined | SiteConfig}
      */
@@ -623,6 +624,7 @@ class Site {
         .then(() => this.collectBaseUrl())
         .then(() => this.collectUserDefinedVariablesMap())
         .then(() => this.collectPlugins())
+        .then(() => this.collectPluginSiteHooks())
         .then(() => this.collectPluginSpecialTags())
         .then(() => this.buildAssets())
         .then(() => (this.onePagePath ? this.lazyBuildSourceFiles() : this.buildSourceFiles()))
@@ -654,6 +656,8 @@ class Site {
    * Build all pages of the site
    */
   buildSourceFiles() {
+    this.runBeforeSiteGenerateHooks();
+
     return new Promise((resolve, reject) => {
       logger.info('Generating pages...');
       this.generatePages()
@@ -685,6 +689,8 @@ class Site {
    * Only build landing page of the site, building more as the author goes to different links.
    */
   lazyBuildSourceFiles() {
+    this.runBeforeSiteGenerateHooks();
+
     return new Promise((resolve, reject) => {
       logger.info('Generating landing page...');
       this.generateLandingPage()
@@ -708,6 +714,7 @@ class Site {
   _rebuildAffectedSourceFiles(filePaths) {
     const filePathArray = Array.isArray(filePaths) ? filePaths : [filePaths];
     const uniquePaths = _.uniq(filePathArray);
+    this.runBeforeSiteGenerateHooks();
 
     return new Promise((resolve, reject) => {
       this.regenerateAffectedPages(uniquePaths)
@@ -727,6 +734,7 @@ class Site {
     const uniqueUrls = _.uniq(normalizedUrlArray);
     uniqueUrls.forEach(normalizedUrl => logger.info(
       `Building ${normalizedUrl} as some of its dependencies were changed since the last visit`));
+    this.runBeforeSiteGenerateHooks();
 
     /*
      Lazy loading only builds the page being viewed, but the user may be quick enough
@@ -988,6 +996,15 @@ class Site {
     }));
   }
 
+  /**
+   * Collect the before site generate hooks
+   */
+  collectPluginSiteHooks() {
+    this.pluginsBeforeSiteGenerate = Object.values(this.plugins)
+      .filter(plugin => plugin.beforeSiteGenerate)
+      .map(plugin => plugin.beforeSiteGenerate);
+  }
+
   /**
    * Collects the special tags of the site's plugins, and injects them into the parsers.
    */
@@ -1016,6 +1033,13 @@ class Site {
     };
   }
 
+  /**
+   * Executes beforeSiteGenerate hooks from plugins
+   */
+  runBeforeSiteGenerateHooks() {
+    this.pluginsBeforeSiteGenerate.forEach(cb => cb());
+  }
+
   /**
    * Creates the supplied pages' page generation promises at a throttled rate.
    * This is done to avoid pushing too many callbacks into the event loop at once. (#1245)
diff --git a/packages/core/src/plugins/default/markbind-plugin-plantuml.js b/packages/core/src/plugins/default/markbind-plugin-plantuml.js
index 342f2e58a2..aa6985e9c2 100644
--- a/packages/core/src/plugins/default/markbind-plugin-plantuml.js
+++ b/packages/core/src/plugins/default/markbind-plugin-plantuml.js
@@ -68,9 +68,10 @@ function generateDiagram(imageOutputPath, content) {
 }
 
 module.exports = {
-  preRender: (content, pluginContext, frontmatter, config) => {
+  beforeSiteGenerate: () => {
     processedDiagrams.clear();
-
+  },
+  preRender: (content, pluginContext, frontmatter, config) => {
     // Processes all <puml> tags
     const $ = cheerio.load(content);
     $('puml').each((i, tag) => {