ZooKeeper JavaScript Implementation<\/p>\n\n\n\n
Def from Apache<\/em>: ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.<\/p>\n\n\n\n ZooKeeper Node Class Structure:<\/p>\n\n\n ZooKeeper Implementation:<\/p>\n\n\n Execution:<\/p>\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" ZooKeeper JavaScript Implementation Def from Apache: ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. ZooKeeper Node Class Structure: ZooKeeper Implementation: Execution:<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[43,44,15,35,1],"tags":[38,39,37,41,42,40],"class_list":["post-329","post","type-post","status-publish","format-standard","hentry","category-algos","category-data-structures","category-javascript","category-nodejs","category-uncategorized","tag-algos","tag-distributed","tag-ds","tag-mq","tag-sqs","tag-synchronization"],"_links":{"self":[{"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/329","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/comments?post=329"}],"version-history":[{"count":3,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/329\/revisions"}],"predecessor-version":[{"id":333,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/329\/revisions\/333"}],"wp:attachment":[{"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/media?parent=329"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/categories?post=329"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bhoomabrsr.com\/blog\/index.php\/wp-json\/wp\/v2\/tags?post=329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\nclass ZooNode {\n key = null;\n value = null;\n watchers = [];\n children = [];\n constructor(key, value, watcherFn) {\n this.key = key;\n this.value = value;\n if (watcherFn) {\n this.watchers.push(watcherFn);\n }\n }\n}\n<\/pre><\/div>\n\n\n\n\nclass ZooKeeper {\n root = new ZooNode('root');\n\n \/*get path segments*\/\n getPathSegments(path) {\n const ps = path.split('\/');\n ps.shift();\n return ps;\n }\n\n \/*call watchers*\/\n callWatchers(fns) {\n fns.forEach(fn => fn?.());\n }\n\n \/*find a node and it's watchers*\/\n dfs(root, pathSegments, idx, watcherFns = []) {\n if (!pathSegments.length) {\n return { node: root, watcherFns: [...root.watchers] };\n }\n const key = pathSegments[idx];\n watcherFns = watcherFns.concat(root.watchers);\n const nodeIdx = root.children.map(p => p.key).indexOf(key);\n if (nodeIdx > -1) {\n const nextRoot = root.children[nodeIdx];\n if (pathSegments.length === idx + 1) {\n watcherFns = watcherFns.concat(nextRoot.watchers);\n return { node: nextRoot, watcherFns };\n }\n return this.dfs(nextRoot, pathSegments, idx + 1, watcherFns);\n }\n }\n\n create(path, value) {\n const ps = this.getPathSegments(path, true);\n const newChildKey = ps.pop();\n const { node: parentNode, watcherFns } = this.dfs(this.root, ps, 0) || {};\n if (parentNode) {\n parentNode.children.push(new ZooNode(newChildKey, value));\n this.callWatchers(watcherFns);\n } else {\n console.log(`unable to add, path is not exist: ${path}`);\n }\n }\n\n setValue(path, value) {\n const ps = this.getPathSegments(path, true);\n const { node, watcherFns } = this.dfs(this.root, ps, 0) || {};\n if (node) {\n node.value = value;\n this.callWatchers(watcherFns);\n } else {\n console.log(`unable to update, path is not exist: ${path}`);\n }\n }\n\n getValue(path) {\n const ps = this.getPathSegments(path, true);\n const { node } = this.dfs(this.root, ps, 0) || {};\n if (node) {\n return node.value;\n } else {\n console.log(`unable to update, path is not exist: ${path}`);\n }\n }\n\n watch(path, fn) {\n const ps = this.getPathSegments(path, true);\n const { node } = this.dfs(this.root, ps, 0) || {};\n if (node) {\n node.watchers = [fn];\/\/concat for multiple listeners\n } else {\n console.log(`unable to update, path is not exist: ${path}`);\n }\n }\n}\n<\/pre><\/div>\n\n\n\nlet z = new ZooKeeper();\nz.create('\/a', 'foo');\nz.create('\/a\/c', 'bar');\nz.create('\/a\/d', 'foo_d');\nz.setValue('\/a\/d', 'foo_d_update');\nconsole.log(z.getValue('\/a\/d')); \n\/\/foo_d_update\n\nz.watch('\/a\/d', () => { console.log('a watch at \/a\/d') });\nz.watch('\/a', () => { console.log('a watch at \/a') });\nz.setValue('\/a\/d', 'foo_d_update_again'); \n\/\/1. a watch at \/a \n\/\/2. a watch at \/a\/d\n\nz.setValue('\/a', 'foo_a_update_again');\n\/\/a watch at \/a\n<\/pre><\/div>\n\n\n