Author Archives: Robins

Hadoop — HDFS data writing process

HDFS write data flow

Suppose there is a local file data.txt First, the HDFS client creates a connection object file system. Then the client requests the namenode to upload the file/user/fzl/ data.txtNameNode After receiving the request, respond to the client and upload the file. The client requests to upload the first block (0-128m), please return to datanode, and then namenode returns datanode1, datanode2, datanode3 nodes (considering node distance, load balancing and other factors), indicating that these three nodes will be used to store data. After receiving the return node, the client creates fsdataoutputstream, and then requests datanode1 to establish a block transmission channel, and datanode1 requests to communicate with Da Tanode2 establishes a channel, datanode2 establishes a channel with datanode3, datanode3 responds to datanode2, datanode2 responds to datanode1, datanode1 responds to fsdataoutputstream successfully (pipeline transmission), and then starts to send data in the form of packet (each transmission of stream is a chunk (512byte), saves a packet (64K) and then transmits the packet object). When transmitting to datanode1, datan Ode1 writes the data file to the disk first, and then transfers it to datanode2 directly from memory. Datanode2 and datanode3 are in turn and so on. In this way, the problem that a datanode fails to write after an error is avoided. After all transfers are completed, a data write operation is completed

The flow chart is as follows:

Node distance calculation

Node distance: the sum of the distances from two nodes to the nearest common ancestor

Figure 2-10: node distance: 3

Rack aware

The first copy is on the node where the client is located. If the client is outside the cluster, randomly select a second replica in a random node of another rack, and the third replica in a random node of the rack where the second replica is located

Error evaluating expression

https://blog.csdn.net/xiuxiuzhuanshu/article/details/78296183

Error information:

Error evaluating expression : 

Source text: deposit receipt

……

Caused by: groovy.lang.MissingPropertyException : no such property: Gold receipt for class: Report_ test_ 1508483943865_ 782998

……

solve:

Using component problems

Originally, it should be a static text, the text is: deposit receipt
uses a text field, and when printing, there is no get method for the “deposit receipt” field in the bean

Error: JMeter monitors Linux system performance java.net.ConnectException : Connection timed out: connect

Question:

JMeter monitors Linux system performance and reports an error:

ERROR: java.net.ConnectException : Connection timed out: connect

reason:

Before the Linux system firewall opened

terms of settlement:

Enter the/usr/bin directory and execute the command/bin/systemctl stop iptables.service Turn off firewall

Problem solving

Note: this method is only for the above problems, other reasons please find other methods, thank you.

 

Error: EBUSY: resource busy or locked

Error: EBUSY: resource busy or locked, LSTAT ‘C:\ swapfile.sys ’。
Here are some effective methods I summarized:

Method 1: delete node_ Module, and then install (NPMI);
method 2: delete node_ Modules, run NPM cache clean or NPM cache clean — force command, and then install;
method 3: upgrade the node version and delete the node_ Modules, and then install it.

Redis cluster error: (error) moved solution

When using redis cli to connect the redis cluster for data operation, an error is reported

./redis-cli -h 192.24.54.1 -p 6379 -a '123456'
192.24.54.1:6379> get name
(error) MOVED 5798 192.24.54.2:6379

resolvent:

This situation is generally caused by not setting the cluster mode when starting redis cli .

When starting, use the - C parameter to start the cluster mode. The command is as follows:

./redis-cli -h 192.24.54.1 -p 6379 -a '123456' -c
192.24.54.1:6379> get name
-> Redirected to slot [5798] located at 192.24.54.2:6379
"yayun"

IAR compilation error [lp011]: Section placement failed

IAR compilation error [lp011]: Section placement failed
unable to allocate space for sections/blocks with a total estimated minimum size of 0x215e bytes (max align 0x1) in & lt; [0x008000-0x009fff] & gt; (total uncommitted space 0x1f80)

IAR compilation error [lp011]: Section placement failed

The error report is as follows:

the solutions are as follows:

Select project – & gt; options – & gt; C/C + + compiler – & gt; optimizations, change the level from low to high, click OK and compile again.

The error disappears:

Solve MySQL error 2002 (HY000)

Error 2002 (HY000): can’t connect to local MySQL server through socket ‘/ var/run/mysqld/ mysqld.sock ’ (2)

When starting mysql, it appears:

because I haven’t used MySQL under Ubuntu for a long time, I thought my password was wrong, and I repeatedly lost it several times. I found that it’s still like this. I also checked the related blogs on the Internet and found that it can’t work. Generally, this kind of error appears on the Internet, which is a bit similar to

In fact, it’s not the same. Pay attention to distinguish the following folders, so go to the configuration file of Mysql to see where the socket folder is, and the configuration file of MySQL is in
/etc/MySQL/ my.cnf In this, cat has a look:

found this sentence remember to edit So when you install mysql, the MySQL Server package is not installed (I don’t know how to get in before, ha ha), so you can install this package

you can also check whether there is this package first

so after installing mysql-server-5.7, you can enter the root password.
A289885427
now my.cnf There is no previous sentence

After matlab2017b is activated, open the error reporting license manager error – 8

When installing, I read the tutorial and said that after activation, I need to crack the dynamic library file under the “crack” folder“ libmwservices.dll ”Replace it with “r2015b/bin/win64” under the installation directory of MATLAB 2015b\ libmwservices.dll ”

But I don’t have it in my crack file libmwservices.dll File… It’s strange that I downloaded the crack file again, but it’s still the same… Maybe it’s a version problem
or not

Finally, a practical method is found in another blog https://blog.csdn.net/m0_ 37638031/article/details/78982498

This blog contains not only the installation package of MATLAB, but also detailed and practical tutorials, especially the last step after activation

The specific steps are as follows:

After activation, copy the netapi32.dll file under the crack file (path as follows: MATLAB r2017b win64 crack/r2017b/bin/win64/netapi32.dll) directly to the installed matlab file (path as follows: C:// program files/Matlab/r2017b/bin/win64).

And then it’s working.

Swift error: abort trap: 6

report errors:

Error: abort trap: 6 when using the third party framework of Gaode map in swift project

resolvent:

In project settings, select build settings – & gt; swift compiler – code generation – & gt; optimization level

Set the optimization level to optimize for size [- osize]

Solution to error: no devices found in ADB command

1： Preface

Recently, the domain name was upgraded. Because the test server is an intranet, the built test domain name cannot be resolved. The hosts file of the mobile phone needs to be modified. An error occurred when using the ADB command to obtain the root permission. Take this as a record.

Equipment: Xiaomi 4C

MIUI is: miui10 development version

The BL lock has been unlocked and the root permission has been obtained, but it is found that the hosts file can not be modified, and the system file lock needs to be unlocked. Therefore, the ADB command is used to unlock the system file lock. It is found that the device cannot be found due to the error. Two solutions are found, which can be tried by the blogger himself. The second solution is used by the blogger.

2： Solutions

The first one is the first one

1. First check who is occupying the port of 5037?Netstat – AON | findstr 5037

2. Kill the process that occupies the port.

3. If you start over, it will work well. However, bloggers are an exception, and still haven’t found the device list…

ADB devices — View devices

Second:

ADB reboot EDL or ADB reboot is OK. After the device is rebooted, it will work again.

3： Conclusion

If you also have this problem, you can try this method. I hope it can help you. If you are also a Xiaomi device and want to unlock or get the highest root permission, you can send a private message to me. I want a tutorial or tool.

I wish you success in your work!

Error: invalid permission for adding an object to repository database 

➜  atd git:(b4.232) ✗ git pull
remote: Counting objects: 78, done.
remote: Compressing objects: 100% (77/77), done.
remote: Total 78 (delta 60), reused 0 (delta 0)
error: insufficient permission for adding an object to repository database .git/objects
fatal: failed to write object
fatal: unpack-objects failed

Git error

insufficient permission for adding an object to repository database 

Because the. Git directory of the project has the permission of root,

The solution is to switch to the root super administrator and modify the user of the file as the current computer user

chown -R xxxx: .git