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java.sql.BatchUpdateException: IO Error: Connection reset

InPractice — Mon, 20 Feb 2017 01:28:00 GMT

during analysis of "IO Error: Connection reset", many articles mentioned that it could be caused by java security code (accessing /dev/random) used in JDBC connection. However it is not the root cause in my case. In my environment, Java already use /dev/urandom. 1. $JAVA_HOME/jre/lib/security/java.security securerandom.source=file:/dev/./urandom 2. check with strace. only -Djava.security.egd=file:/dev/../dev/urandom will trigger system call (read on /dev/urandom) all other other path format like below are OK. -Djava.security.egd=file:/dev/./urandom -Djava.security.egd=file:///dev/urandom 3. Keep checking the retropy size, I have never seen it is exhaused. while [ 1 ]; do cat /proc/sys/kernel/random/entropy_avail sleep 1 done usually the avail is in the range from 1000 to 3000. so far, there is no clue about the root cause of "IO Error: Connection reset".

InPractice 2017-02-20 09:28 发表评论

Lessons learned - Oracle GI and Database Installation on SUSE 12

InPractice — Thu, 28 Jul 2016 08:55:00 GMT

I encountered many issue during installation of Oracle Grid Infrastructure(GI) and Database; with the help of ariticle and documents found through Google search engine, I finally made it. for records, here is the details issues encountered and solutions applied. Major issues were encountered during GI installation. Pre-installation tasks. Issue 1: swapspace is not big enough; (1.3.1 Verify System Requirements) grep MemTotal /proc/meminfo 264G grep SwapTotal /proc/meminfo 2G during OS installation, I take default option and swap space is only 2G. Oracle recommend to have more than 16G swap space in case of more that 32G RAM. dd if=/dev/zero of=/home/swapfile bs=1024 count=33554432 33554432+0 records in 33554432+0 records out 34359738368 bytes (34 GB) copied mkswap /home/swapfile mkswap /home/swapfile chmod 0600 /home/swapfile lessons learned: setup swap space properly according to DB requirement when installing OS. Issue 2: cannot find oracleasm-kmp-default from Oracle site. (1.3.6 Prepare Storage for Oracle Automatic Storage Management) install oracleasmlib and oracleasm-support is easy, just download them from Oracle and install them; Originally oracleasm kernel is provided by Oracle, but now I cannot find it from Oracle; finally I realized that oracleasm kernel is now provided by OS vendor; In my case, it should be installed from SUSE disk; a. to get its name oracleasm-kmp-default zypper se oracle b. map dvd and install zypper in oracleasm-kmp-default rpm -qa|grep oracleasm oracleasm-kmp-default-2.0.8_k3.12.49_11-3.20.x86_64 oracleasm-support-2.1.8-1.SLE12.x86_64 oracleasmlib-2.0.12-1.SLE12.x86_64 asm configure -i asm createdisk DATA /dev/<...> asm listdisks --DATA ls /dev/oracleasm/disks Installation tasks: Issue 3: always failed due to user equivalence check after starting installer OUI with user oracle. however if I manully check with runcluvfy, no issue found at all. ./runcluvfy.sh stage -pre crsinst -n , -verbose I worked around it by using another user to replace user oracle. but it triggered next issue. Issue 4: cannot see ASM disks in OUI. no matter how I change the disk dicovery path. the disk list is empty. but I can find disk manully. /usr/sbin/oracleasm-discover 'ORCL:*' Discovered disk: ORCL:DATA Root cause is that the ASM is configured and created with user oracle. and I aming installing GI with different user other than oracle; so I cannot see the Disk created. change owner of disk device file solved the issue. ls /dev/oracleasm/disks chown /dev/oracleasm/disks -R Issue 5: root.sh execution failed. Failed to create keys in the OLR, rc = 127, Message: clscfg.bin: error while loading shared libraries: libcap.so.1: cannot open shared object file: No such file or directory fixed the issue with command below: zypper in libcap1 ohasd failed to start Failed to start the Clusterware. Last 20 lines of the alert log follow: 2016-07-24 23:10:28.502: [client(1119)]CRS-2101:The OLR was formatted using version 3. I found a good document from SUSE, Oracle RAC 11.2.0.4.0 on SUSE Linux Enterprise Server 12 - x86_64, it make it clear that SUSE 12 is supported by Oracle GI 11.2.0.4, it also mentioned Patch 18370031. "During the Oracle Grid Infrastructure installation, you must apply patch 18370031 before configuring the software that is installed. " The patch 18370031 is actually mentioned in "Oracle quick installation guide on Linux", but not mentioned in "Oracle quick installation guide on Linux". I majored followed up with later one and missed Patch 18370031. issue disappeared after I installed the patch 18370031. ./OPatch/opatch napply -oh -local /18370031 Errors in file : ORA-27091: unable to queue I/O ORA-15081: failed to submit an I/O operation to a disk ORA-06512: at line 4 solved by change owner of disk DATA related file ls -l /dev/oracleasm/iid chown on folder /dev/oracleasm/iid and some .* hidden file. Issue during DB installation Issue 6: report error: in invoking target 'agent nmhs' vi $ORACLE_HOME/sysman/lib/ins_emagent.mk Search for the line $(MK_EMAGENT_NMECTL) Change it to: $(MK_EMAGENT_NMECTL) -lnnz11 refer to https://community.oracle.com/thread/1093616?tstart=0

InPractice 2016-07-28 16:55 发表评论

InPractice — Sat, 01 Apr 2006 01:26:00 GMT

J2EE��目中基本都是遵循分层架构的�Q�自然包�l�构也是��Z��分层的。DAO层有DAO package。service 层有service package。在�q�些包下面再�Ҏ��模块划分子包�?br />
我觉得另一�U�可行的�Ҏ��是根据模块划分包�Q�如果包比较复杂�Q�比如有��过十个的类�Q�再�Ҏ��层来划分子包。一般的模块比较��单，无需划分子包�?br />
从高内聚�Q�低偶合的原则来��_��q�样划分��h��更高的内聚性。如果按层划分。其实同层的�c�dƈ入多大的关系。考虑一下DAO层。这些DAO之间有多��联�p�？

新划分方法的好处是如果需要修�Ҏ��个模块，修改的地方相寚w��中。因为都位于一个包内�?br />
现在分层架构已经非常普遍�Q�没有必要在包的划分上体现分层架构。在�c�d��上体现分层架构即可。就是说分层架构无需通过包结构来体现�?br />
新的划分�Ҏ��可能有一个问题。各个模块之间可能有实现上的冗余。如果采用这个方案，需要在�q�点上采取预防措施�?br />
当然�q�还是想法，没有在项目中实践。希望大家能指出�q�个�Ҏ��可能带来的问题�?br />

InPractice 2006-04-01 09:26 发表评论

InPractice — Sun, 19 Feb 2006 10:01:00 GMT

每次��目�l�束�Q�都会发现有一堆的Bug。如何分析这些Bug�Q�避免重�y�覆辙�?br />
有两�U�分析方法， �Ҏ��Developer在修复Bug旉��择的CommonCause�Q�选择比重最大的CommonCause�Q?br />
然后从各个方面分析RootcCause。�ȝ��出可以改�q�的地方�?br />
我很隄��解这�U�方法，主要是觉得每�ơ都是泛泛而谈�Q�对减少BUG没有真正的帮助�?/font>

(我确信这�U�分析方法没有太大的意义,因�ؓ�~�Z��对底层原因的了解. 而且Developer在选择common Cause的时候完全可能没有合适的而�Q选一�?�l�常看到的一个例子是�~�Z��UT. �q�个��׃��一定是真正的原�?事实往往是做了UT却没有发现出Bug.�q�种分析�Ҏ��是典型的不深入实际的��夸作风, 依赖�l�计的数据而没有看到统计数据事实上可能存在问题. �q�样的工作肯定效率不�? )

下面是我的一些思考�?br />分析的基��应该是Bug�Q�而不是commonCause。直接从CommonCause开始分析，臛_��可能遗漏一下重要有价值的发现�?br />有些Bug是有可能避免的。而有些bug可以说没有什么好的对�{�。我们应该集中分析有可能避免的Bug�?br />至于如何分析具体Bug是否能避免，首先应该是造成该Bug的Developer自己分析�Q�让大家知道Bug是如何�Ş成的�Q�然后由大家集体军_��。（�q�样做的风险是大家能否接受。）
其次�Ҏ��Bug引入的时��_��和最�l�测试出的时��_��ȝ��有没有可以改�q�的大方�?br />能够由developer改进而消除的Bug。是最有希望避免再�ơ发生的�?br />比如�Q�有些bug是打字错误造成界面上显�C�的内容有瑕疵，一个可行的改进是每�ơ都从需求文档拷贝�?br />注意必须要有措施能保证该�l�验能被所有Developer知道�?br />另一个例子是�Q�我有一�ơ，是的�Q�我有一�ơ再修正bug是没有清除彻底。在�ȝ��的时候我掌握了全局查找、替换的技巧。有效地避免了类似的错误再次发生�?br />
�q��所有错误都能由devloper来消除，有一些只能由Tester来消除。比如，一般来��_��Tester��L��比Developer对界面敏感，更能发现界面bug�?br />我觉得随着单元��试的进步，现在对Developer的测试水�q�的要求也提高了。这也许不尽合理。developer对实现花了很多精力，他不可能在测试上辑ֈ�同样的水准�?br />

InPractice 2006-02-19 18:01 发表评论

Throw away unnecessary interface!

InPractice — Sun, 19 Feb 2006 09:30:00 GMT

Why we need Interface? The most important benefit come from the fact: The code depend on the interface no need to care about the implementaion class. and if the implementation class is changed later, the client code no need to update.
This is the feature of Ploymophism of OOP, such as Java.

In some projects, the struts framework was adopted, so all the field need to be persisted is in ActionForm. In order to avoid that the Service layer /DAO layer will depends on the struts. One way is to define a interface which have getter and
setter to access all the fields need to be persisted. The design is like this:

XXXActionForm --------> XXXInterface <--------------ServiceLayer/DAO Layer
most of them are
getter and setter

I can understand this concern, it seems follow the paterns in Enterprise Application Architecture Pattern. but I can not agree this kinds of design. I believe this is misuse of interface.

First, in this kinds of design, if we add some fields, we need update the actionForm, them also need to update interface.
It is boring, and in this case, the interface can not provide any abstraction so the interface need to evolve as the implementation changed.

Second, there is only one kind of implementaion in the system, so the interface can not provide the benifit from making use of polymorphism.

In a word, we can get nothing design benefit from Interface in this case, And Have burden to keep the implementaion and interface synchronized.

InPractice 2006-02-19 17:30 发表评论