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https://issues.apache.org/jira/browse/YARN-3336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14372290#comment-14372290
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zhihai xu commented on YARN-3336:
---------------------------------
Oh, that is a good idea. I uploaded a new patch YARN-3336.004.patch, which use
the instance counter for the verification. Please review it.
many thanks [~cnauroth]!
> FileSystem memory leak in DelegationTokenRenewer
> ------------------------------------------------
>
> Key: YARN-3336
> URL: https://issues.apache.org/jira/browse/YARN-3336
> Project: Hadoop YARN
> Issue Type: Bug
> Components: resourcemanager
> Reporter: zhihai xu
> Assignee: zhihai xu
> Priority: Critical
> Attachments: YARN-3336.000.patch, YARN-3336.001.patch,
> YARN-3336.002.patch, YARN-3336.003.patch, YARN-3336.004.patch
>
>
> FileSystem memory leak in DelegationTokenRenewer.
> Every time DelegationTokenRenewer#obtainSystemTokensForUser is called, a new
> FileSystem entry will be added to FileSystem#CACHE which will never be
> garbage collected.
> This is the implementation of obtainSystemTokensForUser:
> {code}
> protected Token<?>[] obtainSystemTokensForUser(String user,
> final Credentials credentials) throws IOException, InterruptedException
> {
> // Get new hdfs tokens on behalf of this user
> UserGroupInformation proxyUser =
> UserGroupInformation.createProxyUser(user,
> UserGroupInformation.getLoginUser());
> Token<?>[] newTokens =
> proxyUser.doAs(new PrivilegedExceptionAction<Token<?>[]>() {
> @Override
> public Token<?>[] run() throws Exception {
> return FileSystem.get(getConfig()).addDelegationTokens(
> UserGroupInformation.getLoginUser().getUserName(), credentials);
> }
> });
> return newTokens;
> }
> {code}
> The memory leak happened when FileSystem.get(getConfig()) is called with a
> new proxy user.
> Because createProxyUser will always create a new Subject.
> The calling sequence is
> FileSystem.get(getConfig())=>FileSystem.get(getDefaultUri(conf),
> conf)=>FileSystem.CACHE.get(uri, conf)=>FileSystem.CACHE.getInternal(uri,
> conf, key)=>FileSystem.CACHE.map.get(key)=>createFileSystem(uri, conf)
> {code}
> public static UserGroupInformation createProxyUser(String user,
> UserGroupInformation realUser) {
> if (user == null || user.isEmpty()) {
> throw new IllegalArgumentException("Null user");
> }
> if (realUser == null) {
> throw new IllegalArgumentException("Null real user");
> }
> Subject subject = new Subject();
> Set<Principal> principals = subject.getPrincipals();
> principals.add(new User(user));
> principals.add(new RealUser(realUser));
> UserGroupInformation result =new UserGroupInformation(subject);
> result.setAuthenticationMethod(AuthenticationMethod.PROXY);
> return result;
> }
> {code}
> FileSystem#Cache#Key.equals will compare the ugi
> {code}
> Key(URI uri, Configuration conf, long unique) throws IOException {
> scheme = uri.getScheme()==null?"":uri.getScheme().toLowerCase();
> authority =
> uri.getAuthority()==null?"":uri.getAuthority().toLowerCase();
> this.unique = unique;
> this.ugi = UserGroupInformation.getCurrentUser();
> }
> public boolean equals(Object obj) {
> if (obj == this) {
> return true;
> }
> if (obj != null && obj instanceof Key) {
> Key that = (Key)obj;
> return isEqual(this.scheme, that.scheme)
> && isEqual(this.authority, that.authority)
> && isEqual(this.ugi, that.ugi)
> && (this.unique == that.unique);
> }
> return false;
> }
> {code}
> UserGroupInformation.equals will compare subject by reference.
> {code}
> public boolean equals(Object o) {
> if (o == this) {
> return true;
> } else if (o == null || getClass() != o.getClass()) {
> return false;
> } else {
> return subject == ((UserGroupInformation) o).subject;
> }
> }
> {code}
> So in this case, every time createProxyUser and FileSystem.get(getConfig())
> are called, a new FileSystem will be created and a new entry will be added to
> FileSystem.CACHE.
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