引用Net::ZooKeeper這個包，可能會報這個錯誤
Can't load '/usr/local/lib64/perl5/auto/Net/ZooKeeper/ZooKeeper.so' for module Net::ZooKeeper: /usr/local/lib64/perl5/auto/Net/ZooKeeper/ZooKeeper.so: undefined symbol: ZOO_PERM_CREATE at /usr/lib64/perl5/XSLoader.pm line 70. at /usr/local/lib64/perl5/Net/ZooKeeper.pm line 109.
查看XSLoader.pm的70行：
70 my $libref = dl_load_file($file, 0) or do {
71 require Carp;
72 Carp::croak("Can't load '$file' for module $module: " . dl_error());
73 };實際上是加載ZooKeeper.so這個動態鏈接庫。我們objdump，看看這個缺少的符號到底有沒有在這個鏈接庫裏面。
[zhangbin@localhost xoa2-perl]$ objdump -x /usr/local/lib64/perl5/auto/Net/ZooKeeper/ZooKeeper.so | grep ZOO 0000000000000000 *UND* 0000000000000000 ZOO_PERM_CREATE 0000000000000000 *UND* 0000000000000000 ZOO_READ_ACL_UNSAFE 0000000000000000 *UND* 0000000000000000 ZOO_PERM_WRITE 0000000000000000 *UND* 0000000000000000 ZOO_ASSOCIATING_STATE 0000000000000000 *UND* 0000000000000000 ZOO_CREATED_EVENT 0000000000000000 *UND* 0000000000000000 ZOO_CONNECTED_STATE 0000000000000000 *UND* 0000000000000000 ZOO_AUTH_FAILED_STATE 0000000000000000 *UND* 0000000000000000 ZOO_EPHEMERAL 0000000000000000 *UND* 0000000000000000 ZOO_SEQUENCE 0000000000000000 *UND* 0000000000000000 ZOO_PERM_READ 0000000000000000 *UND* 0000000000000000 ZOO_CREATOR_ALL_ACL 0000000000000000 *UND* 0000000000000000 ZOO_PERM_ALL 0000000000000000 *UND* 0000000000000000 ZOO_DELETED_EVENT 0000000000000000 *UND* 0000000000000000 ZOO_OPEN_ACL_UNSAFE 0000000000000000 *UND* 0000000000000000 ZOO_PERM_ADMIN 0000000000000000 *UND* 0000000000000000 ZOO_CONNECTING_STATE 0000000000000000 *UND* 0000000000000000 ZOO_EXPIRED_SESSION_STATE 0000000000000000 *UND* 0000000000000000 ZOO_NOTWATCHING_EVENT 0000000000000000 *UND* 0000000000000000 ZOO_PERM_DELETE 0000000000000000 *UND* 0000000000000000 ZOO_CHANGED_EVENT 0000000000000000 *UND* 0000000000000000 ZOO_CHILD_EVENT 0000000000000000 *UND* 0000000000000000 ZOO_SESSION_EVENT
標記爲UND，說明這是一個外部符號，應該是需要引用其他庫，估計是zookeeper庫。但是lib包已經加入了LD_LIBRARY_PATH，非常奇怪。
嘗試重新編譯ZooKeeper.so（源碼在zookeeper的contrib/zkperl下），發現發佈包是用MakeMaker組織的，首先生成Makefile，獲得下面的提示：
[zhangbin@localhost zkperl]$ perl Makefile.PL Warning (mostly harmless): No library found for -lzookeeper_mt Generating a Unix-style Makefile Writing Makefile for Net::ZooKeeper Writing MYMETA.yml and MYMETA.json
注意第一行的warning，這是解決問題的關鍵。Most harmless，but harm this time。查看 Makefile.PL的 第31行
31 GetOptions( 32 'zookeeper-include=s' => \@zk_inc_paths, 33 'zookeeper-lib=s' => \@zk_lib_paths 34 );
可見第二個選項是必須的。
重新編譯。
[zhangbin@localhost zkperl]$ perl Makefile.PL --zookeeper-lib=/home/zhangbin/env/lib Checking if your kit is complete... Looks good Generating a Unix-style Makefile Writing Makefile for Net::ZooKeeper Writing MYMETA.yml and MYMETA.json
然後make && sudo make install。問題解決。
可能XSLoader沒有自動從LD_LIBRARY_PATH尋找可用的庫和符號表的機制。