Docker build with Git command running in CircleCI failing with: Fatal: No names found, cannot describe anything, invalid argument, for "-t, --tag" flag: invalid reference format

Introduction

Context: Docker, CircleCI, Github.

The Docker build command 

docker build -f .circleci/Dockerfile -t $AWS_ACCOUNT_ID.ecr.$AWS_DEFAULT_REGION.amazonaws.com/${CIRCLE_PROJECT_REPONAME}:`git describe --tags` -t $AWS_ACCOUNT_ID.ecr.$AWS_DEFAULT_REGION.amazonaws.com/${CIRCLE_PROJECT_REPONAME}:${CIRCLE_BUILD_NUM} -t $AWS_ACCOUNT_ID.ecr.$AWS_DEFAULT_REGION.amazonaws.com/${CIRCLE_PROJECT_REPONAME}:${CIRCLE_SHA1} .

was failing with this message:

fatal: No names found, cannot describe anything.

invalid argument "********************************************/my-project:" for "-t, --tag" flag: invalid reference format

See 'docker build --help'.

Exited with code exit status 125

Solution

You'd expect the Docker command maybe being syntactically incorrect. But the error message is referring to something else: it turns out the git describe --tags command gave the fatal message.

The cause was that there was no git-tag set at all on the Github project yet.   After manually creating a release (including a tag) on Github and running the above build command again, the docker build command succeeded.

Connection refused Spring Boot application to MySql in Docker solution

Introduction

The Spring Boot Java application was initially using the H2 embedded database, first the in-memory version (losing all data each run), then the file based version. The database structure is created using Liquibase.

Then the requirement was to have the Spring Boot Java application still not dockerized (just started with mvn spring-boot:run), but have it connect to a MySql 8 database than runs inside a Docker container. Most examples you can find have also the Spring Boot application in a Docker container.
The official Spring documentation only shortly mentions the possibility of running MySql in Docker, but no more details on how to do that: https://spring.io/guides/gs/accessing-data-mysql/

This is how the setup should be working:

I set up that docker container using the Windows 10 WSL 1 shell within IntelliJ (note WSL 2 is now recommended):

docker pull mysql/mysql-server:8.0
docker run --name recipesmysql8 -d mysql/mysql-server:8.0

After changing the One Time Password (OTP) for root, creating the database user, creating a 'recipes' database, this is how docker ps looked:

CONTAINER ID        IMAGE                    COMMAND                  CREATED             STATUS                PORTS                       NAMES
3a507fc66690        mysql/mysql-server:8.0   "/entrypoint.sh mysq…"   6 days ago          Up 6 days (healthy)   3306/tcp, 33060-33061/tcp   recipesmysql8

And MySql is indeed running: docker logs recipesmysql8 shows:

2022-08-31T19:02:05.722742Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.30) starting as process 1
2022-08-31T19:02:05.755538Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2022-08-31T19:02:06.104813Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2022-08-31T19:02:06.416522Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2022-08-31T19:02:06.416574Z 0 [System] [MY-013602] [Server] Channel mysql_main configured to support TLS. Encrypted connections are now supported for this channel.
2022-08-31T19:02:06.443572Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '::' port: 33060, socket: /var/run/mysqld/mysqlx.sock
2022-08-31T19:02:06.443740Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.30'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MyS
QL Community Server - GPL.

So all running fine, ports seemed fine. The Spring Boot application configuration for JDBC is this:

spring.datasource.url=jdbc:mysql://localhost:3306/recipes
spring.datasource.username=recipes
spring.datasource.password=mypasswd
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

But then the mvn spring-boot:run gave this relatively vague error:

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    ...
   Caused by: java.net.ConnectException: Connection refused: no further information

So unable to connect, but why? It does not seem an incorrect username/password combination, then I would expect some unauthorized/not authenticated type of message.
Then I found this handy command determining what the real IP should be of the machine that the MySql docker runs in:

docker inspect -f '{{.Name}} - {{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $(docker ps -aq)

I found my MySql container at: /recipesmysql8 - 172.17.0.2
Same result, shorter answer: docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' recipesmysql8
Or even just without the filtering: docker inspect recipesmysql8

So the JDBC configuration I changed to:

spring.datasource.url=jdbc:mysql://172.17.0.2:3306/recipes
spring.datasource.username=recipes
spring.datasource.password=mypasswd
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

But then the mvn spring-boot:run gave this timeout error:

Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    ...
    Caused by: java.net.ConnectException: Connection timed out: no further information

So a similar error message, but this time a connection timeout. Is maybe the problem connecting from within IntelliJ where I execute the mvn spring-boot:run command, to Docker that runs in WSL?

I tried by disabling the antivirus software and local firewall and WIFI, but those didn't work either, at most a different error message like:

Caused by: java.net.NoRouteToHostException: No route to host: no further information

And even with the mysql shell client does it give an error (bit less clear):

mysql -h 172.17.0.2 -P 3306 --protocol=tcp -u root -p
Enter password:
ERROR 2003 (HY000): Can't connect to MySQL server on '172.17.0.2' (11)

Solution

Then I stopped my container, started a new one with explicitly ports-mapping specified:

docker run --name recipesmysql8v2 -p 3306:3306 -d mysql/mysql-server:8.0

docker ps output:
CONTAINER ID        IMAGE                    COMMAND                  CREATED             STATUS                   PORTS
    NAMES
819333cf718e        mysql/mysql-server:8.0   "/entrypoint.sh mysq…"   2 minutes ago       Up 2 minutes (healthy)   0.0.0.0:3306->3306/tcp, :::3306->3306/tcp, 33060-33061/tc
p   recipesmysql8v2

Then a different error message for mysql -h 127.0.0.1 -P 3306 --protocol=tcp -u recipes -p appeared:

ERROR 1130 (HY000): Host '172.17.0.1' is not allowed to connect to this MySQL server

That looked promising.

Note: due to having a new container, I had to reset the OTP for user 'root' again of course. You can find that OTP by issuing docker logs recipesmysqlv2 | grep GENERATED.
Then issue these commands:

docker exec -it your_container_name_or_id bash
mysql -u root -p
Enter password: <enter the one found with the above grep shell command>
ALTER USER 'root'@'localhost' IDENTIFIED BY 'your secret password';

Create the Spring Boot application database again: create database recipes;
Add the Spring Boot application user again: create user 'recipes'@'%' identified by 'L7z$11Oeylh4';

Give that user only the necessary permissions:
grant create, select, insert, delete, update on recipes.* to 'recipes'@'%';

After that, these entries should be in the mysql.user table:
mysql> SELECT host, user FROM mysql.user;
+-----------+------------------+
| host      | user             |
+-----------+------------------+
| %         | recipes          |
| localhost | healthchecker    |
| localhost | mysql.infoschema |
| localhost | mysql.session    |
| localhost | mysql.sys        |
| localhost | root             |
+-----------+------------------+
6 rows in set (0.00 sec)

Note the recipes user entry with host '%', which allows access from any host, which you probably want to make more secure in a production environment. See https://downloads.mysql.com/docs/mysql-secure-deployment-guide-8.0-en.pdf for tips.

Now you should be able to connect from the mysql client prompt in several ways:

mysql -h 127.0.0.1 -P 3306 --protocol=tcp -u recipes -p
mysql -h localhost -P 3306 --protocol=tcp -u recipes -p
mysql -h 0.0.0.0 -P 3306 --protocol=tcp -u recipes -p

Note that the 172.17.0.2 still does not connect! For that to work you'll have to probably add that host to the above mysql.user table (not tried to see if that works).

Instead of mysql client you can also use the standard *nix command telnet to see if at least the port is reachable:

telnet 127.0.0.1 3306
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.

(I don't remember what it showed when the initial issue with the docker container named 'recipesmysql8' was there)

And after starting the Spring Boot application: connection worked and tables and indexes were created!

Note: only from within the docker image can you connect like this: docker exec -it recipesmysql8v2 bash and execute mysql -u root -p after having issued ALTER USER 'root'@'localhost' IDENTIFIED BY 'nR128^n8f3kx';
Because running mysql -h 127.0.0.1 -P 3306 --protocol=tcp -u root -p from within the commandline WSL still gives: ERROR 1045 (28000): Access denied for user 'root'@'172.17.0.1' (using password: YES)

Probable cause: when you only have MySql in a Docker container, it is not in the same "network" as Docker containers, so the port 3306 is not reachable from outside Docker runtime. So you will have to tell Docker how you want to expose the port(s). Another way to solve this is to have the Spring Boot application also as a Docker application; and potentially configure it via docker-compose, see here for an example on how to do this: https://www.javainuse.com/devOps/docker/docker-mysql.

Configuring MySQL test-containers in your Spring Boot Java Integration Tests

Introduction

In your Integration Tests (IT) you often try to use the H2 in-memory database, to improve the speed of your integration tests. But on the other hand you want to mimic the production database as much as possible in your integration-tests.

Setting H2 in MySQL database compatibility mode tries to emulate MySQL as much as possible, but only a small subset of the differences are implemented. What for example not works correctly in H2 for JSON fields is that it escapes strings with "". For that reason you usually want to switch to for example starting a Docker database testcontainer in your IT tests, which uses a real MySQL database. With the Java-specific version in https://github.com/testcontainers/testcontainers-java.

Configuration

There are several good-to-know tips when configuring the testcontainers in your ITs.

1. The simplest configuration is using a datasource URL in the Spring Boot properties file. This has the disadvantage that whatever database name you specify, the testcontainers library still creates a DB named 'test'. So below it will be named 'integration_test_db' you'd think, but it is still named 'test' when the IT runs:
   
   spring.datasource.url=jdbc:tc:mysql:5.7.32:///integration_test_db?sessionVariables=sql_mode='STRICT_TRANS_TABLES'&TC_MY_CNF=mysql&TC_INITSCRIPT=mysql/init_mysql_integration_tests.sql
   
   To be able to do everything on the started database, including giving it the name you want, use this URL (or see below the Java version). Notice the user 'root' in the URL:
   spring.datasource.url=jdbc:tc:mysql:5.7.32:///integration_test_db?user=root&password=&sessionVariables=sql_mode='STRICT_TRANS_TABLES'&TC_MY_CNF=mysql&TC_INITSCRIPT=mysql/init_mysql_integration_tests.sql
   
   Via: https://github.com/testcontainers/testcontainers-java/issues/932
   
   
2. To initialize your database, specify the script via this extra datasource URL variable:
   
   TC_INITSCRIPT=mysql/init_mysql_integration_tests.sql
   
   Note the default directory it looks in is ..../resources for the scripts. So the full path is ..../resources/mysql/
   
   
3. An example to prevent GROUP BY error from strict mode, add this in your TC_INITSCRIPT:
   
   SET GLOBAL sql_mode = 'STRICT_TRANS_TABLES';
   SET SESSION sql_mode = 'STRICT_TRANS_TABLES';
   
   
4. To configure it in the IT Java class itself:
   
   @RunWith(SpringRunner.class)
   @SpringBootTest(classes = { SomeClassA.class, SomeClassB.class, ApplicationConfiguration.class}, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
   @TestPropertySource(locations = {
           "classpath:/application-test-mysql.properties" })
   @ContextConfiguration(initializers = {ThisITClass.Initializer.class})
   
   static class Initializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
           public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
               TestPropertyValues.of(
                       "spring.datasource.url=" + mySQLContainer.getJdbcUrl(),
                       "spring.datasource.username=" + mySQLContainer.getUsername(),
                       "spring.datasource.password=" + mySQLContainer.getPassword()
               ).applyTo(configurableApplicationContext.getEnvironment());
           }
       }
   
   @ClassRule
   public static MySQLContainer mySQLContainer = new MySQLContainer<>("mysql:5.7.31")
               .withUsername("root") // So now you can do a GRANT too for example
               .withPassword("") // Only possible for user 'root'
               .withEnv("MYSQL_ROOT_HOST", "%")
               .withDatabaseName("integration_test_db") // So this name will now be used, not 'test'
               .withInitScript("mysql/init_mysql_integration_tests.sql")
               ;
   
   
5. The MySQL docker image used in the tests is retrieved from DockerHub https://hub.docker.com/_/mysql
   
   

Gitlab maven:3-jdk-8 Cannot get the revision information from the scm repository, cannot run program "git" in directory error=2, No such file or directory

Introduction

In a Gitlab project setup the most recent Docker image for maven was always retrieved from the internet before each run by having specified image: maven:3-jdk-8 in the gitlab-ci.yml. The image details can be found here.

Of course this is not a best-practice; your build can suddenly start failing at a certain point because an update to the image might have something changed internally causing things to fail.

What you want is controlled updates. That way you can anticipate on builds failing and plan the upgrades in your schedule.

The issue and workarounds/solutions

And indeed suddenly on March 29 2018 our builds started failing with this error:

[ERROR] Failed to execute goal org.codehaus.mojo:buildnumber-maven-plugin:1.4:create (useLastCommittedRevision) on project abc: Cannot get the revision information from the scm repository :
[ERROR] Exception while executing SCM command.: Error while executing command. Error while executing process. Cannot run program "git" (in directory "/builds/xyz"): error=2, No such file or directory

That message is quite unclear: is git missing? Or is the directory wrong? Or could the maven buildnumber plugin not find the SCM repository?

After lots of investigation it turned out the maven:3-jdk-8 image indeed had changed about 18 hours before.

And after running the maven command in a local version of that Docker image indeed the same error occured!  Awesome, the error was reproducable.

And after installing git again in the image with:

- apt-get update
- apt-get install git -y

the error disappeared!  But a new one appeared:

[ERROR] The forked VM terminated without properly saying goodbye. VM crash or System.exit called?

This also hadn't happened before. After some searching it turned out it might be the surefire and failsafe plugins being outdated.

So I updated them to 2.21.0 and indeed the build succeeded.

Here's the issue reported in the Docker Maven github. UPDATE: it is caused by an openjdk issue (on which the maven:3-jdk-8 is based upon.

This issue made us realize we really need an internal Docker repository. And so we implemented that :)

One disadvantage about Docker images is that you can't specify a commit hash to use. Yes you can specify a digest instead of a tag, but that is a unique UUID hashcode only. You can't see from that hashcode anymore the (related) tagname.

Lessons learned Docker microservices architecture with Spring Boot

Introduction

During my last project consisting of a Docker microservices architecture, built with Spring Boot, using RabbitMQ as communication channel, I learned a bunch of lessons, here's a summary of them.

Architecture

Below is a high level overview of the architecture that was used.

Docker

• Run 1 process/service/application per docker container (or put stuff in init.d but that's not intended use of docker)


• Starting background processes in the CMD cause container to exit. So either have a script waiting at the end (e.g tail -f /dev/null) or keep the process (i.e the one prefixed with CMD) running in the foreground. Other useful Dockerfile tips you can find here


• As far as I can tell Docker checks if Dockerfile has changed, and if so, creates a new image instance (diffs only?)


• Basic example to start RabbitMq docker image, as used in the build tool:
  
  $ docker pull 172.18.19.20/project/rabbitmq:latest
  $ docker rm -f build-server-rabbitmq
  $ # Map the RabbitMQ regular and console ports
  $ docker run -d -p 5672:5672 -p 15672:15672 --name build-server-rabbitmq 172.18.19.20/rabbitmq:latest


• If there's no docker0 interface (check by running command ifconfig) then probably there are ^M characters in the config file at /etc/default/docker/docker.config. To fix it, perform a dos2unix on that file.


• Check for errors at startup of docker in /var/log/upstart/docker.log


• If your docker push <image> asks for a login (and you don't expect that) or it returns some weird html like "</html>" then you're probably missing the host in front of the image name, e.g: 172.18.19.20:6000/projectname/some-service:latest


• Stuff like /var/log/messages is not visible in a Docker container, but is in its host! So look there for example to find out why a process is not starting/gets killed at startup without any useful logging (like we had with clamd)


• How to remove old dangling unused docker images: docker rmi $(docker images --filter "dangling=true" -q --no-trunc)

Spring Boot

• Some jackson2 dependencies were missing from the generated Spring Initializr project, noticed when creating unittests. These dependencies were additionally needed in scope test:
  
  <dependency>
    <groupid>com.fasterxml.jackson.core</groupid>
    <artifactid>jackson-databind</artifactid>
    <version>2.5.0</version></dependency>
  <dependency>
    <groupid>com.fasterxml.jackson.core</groupid>
    <artifactid>jackson-annotations</artifactid>
    <version>2.5.0</version></dependency>
  <dependency>
    <groupid>com.fasterxml.jackson.core</groupid>
    <artifactid>jackson-core</artifactid>
    <version>2.5.0</version></dependency>
  
  Not sure anymore why these then didn't get <scope>test</scope> then... Guess it was needed also in some regular code... :)


• In the Spring Boot AMQP Quick Start the last param has name .with(queueName) during binding, but that's the topic key! (which is related to the binding key used at sending), so not the queue name.


• Spring Boot Actuator's /health will check all related dependencies! So if you have a dependency in your pom.xml to a project which uses spring-boot-starter-amqp, /health will check now for an AMQP queue being up! So add a for those if you don't want that.


• Spring Boot's default AppAplicationIT probably needs a @DirtiesContext for your tests, otherwise the tests might re-use or create more beans than you think (we saw that in our message receiver tests helper class).


• @Transactional in Spring: by default only for unchecked exceptions!! It's documented but still a thing to watch out for.


• And of course: Spring's @Transactional does not work on private methods (due to proxy stuff it creates)


• To see in Spring Boot the transaction logging, put this in application.properties:
  
  logging.level.org.springframework.jdbc=TRACE
  logging.level.org.springframework.transaction=TRACE
  
  Note that by default @Transactional just rolls back, it does not log anything, so if you don't log your runtime exceptions, you won't see much in your logs.


• mockMvc from spring is not really invoking from "outside", our spring sec context filter (for which you can use @Secured(role)) was allowing calls while no authentication was provided for. RestTemplate seems to work from "the outside".


• Scan order can mess up @ControllerAdvice error handler it seems. Had to change the order sometimes:
  
  Setup:
  - Controller is in: com.company.request.web.
  - General error controller is in com.company.common package.
  
  Had to change
  @ComponentScan(value = {"com.company.security", "com.company.common", "com.company.cassandra", "com.company.module", "com.company.request"})
  
  to
  
  @ComponentScan(value = {"com.company.security", "com.company.cassandra", "com.company.module", "com.company.request", "com.company.common"})
  
  Note that the general error controller has now been put in last


• Spring Boot footprint seems relatively big especially for microservices. At least 500MB or something is needed, so we have quite big machines for about 20 services. Maybe plain Spring (iso Spring boot) might be more lightweight...

Bamboo build server

• When Bamboo gets slow and the CPU seems quite busy and memory availability on its server seems fine, increase the Xmss and Xmsx (or related). Found this out because the java Bamboo process was running out of heap sometimes, increasing heap also fixed performance.


• To have Bamboo builds fail on quality gates not met in SonarQube, install in Sonar the build breaker plugin. See the plugin docs and Update Center. This FAQ says so.

Stash

• The Stash (now called Bitbucket) API: in /rest/git/1.0/projects/{projectKey}/repos/{repositorySlug}/tags a 'slug' is just a repository name. 

Microservices with event based architecture

• When you do microservices, IMMEDIATELY take into account during coding + reviews that multiple instances can do concurrent access to database.
  
  This has affect on your queries. Most likely correct implementation for uniqueness check on inserts:
  1- add unique constraint
  2- run insert
  3- catch uniqueness exception --> you know it already exists. Solution with SELECT NOT EXISTS is not guaranteed unique.


• Also take deleting of data (e.g user deletes himself) into account from the start. Especially when using events and/or eventual consistency in combination with an account-balance or similar. Because what if one services in the whole chain of things to execute for a delete fails? Has the user still some money left on his/her account then? In short: take care of CRUD.


• Multiple services are sending the same event? That can indicate 2 services are doing the same thing --> Not good probably.


• Microservices advantages:
  
  - Forces you to better think about where to put stuff in comparison to monolith where you more often can be tempted to "just do a quick fix".
  - language independency for service implementation: choose the best language for the job
  
  Disadvantages:
  - more time needed for design
  - eventual consistency is quite tough to understand & work with, also conceptually
  - infrastructure is more complex including all communication between services
  
  More cons can be found here.

Tomcat

• Limit the maximum size of what can be posted to a servlet is not as easy as it seems for REST services:
  
  - maxPostSize in Tomcat is enforced only for specific contenttype: Tomcat only enforces that limit if the content type is application/x-www-form-urlencoded
  
  - And the other 3 below XML options are for multipart only:
  
  <multipart-config>
    <!-- 52MB max -->
    <max-file-size>52428800</max-file-size>
    <max-request-size>52428800</max-request-size>
    <file-size-threshold>0</file-size-threshold></multipart-config>
  
  So that one won't work for uploading just a byte[]. The only solution is in the servlet (e.g Spring @Controller) you'll have to check for the limit you want to allow.


• maxthreads seems set to be unlimited by default or something. 50 seems to perform better. (workerthreads) 

Security

• To securely generate a random number: SecureRandom randomGenerator = SecureRandom.getInstance("NativePRNG");


• Good explanation of secure use of a salt to use for hashing can be found here. 

Cassandra

• Unique constraints are not possible in Cassandra, so there you will even have to implement unique constraints in the business logic (and make it eventually consistent)


• CassandraOperations query for one field:
  
  Select select = QueryBuilder.select(MultiplePaymentRequestRequesterEntityKey.ID).from(MultiplePaymentRequestRequesterEntity.TABLE_NAME);
  select.setConsistencyLevel(ConsistencyLevel.LOCAL_QUORUM);
  select.where(QueryBuilder.eq(MultiplePaymentRequestRequesterEntityKey.REQUESTER, requester));
  return cassandraTemplate.queryForList(select, UUID.class);
  
  See also here.


• Note below two keys don't seem to get picked up by Cassandra in the Spring Data Cassandra version 1.1.4.RELEASE:  
  
  <groupid>org.springframework.data</groupid>
  <artifactid>spring-data-cassandra</artifactid>
  
  @PrimaryKeyColumn(name = OTHER_USER_ID, ordinal = 0, type = PrimaryKeyType.PARTITIONED)
  @CassandraType(type = DataType.Name.UUID)
  private UUID meUserId;
  
  @PrimaryKeyColumn(name = ME_USER_ID, ordinal = 1, type = PrimaryKeyType.CLUSTERED)
  @CassandraType(type = DataType.Name.UUID)
  private UUID meId;
  This *does* get picked up: put it into a separate class:
  
  @Data
  @AllArgsConstructor
  @PrimaryKeyClass
  public class HistoryKey implements Serializable {
  
    @PrimaryKeyColumn(name = HistoryEntity.ME_USER_ID, ordinal = 0, type = PrimaryKeyType.PARTITIONED)
    @CassandraType(type = DataType.Name.UUID)
    private UUID meUserId;
  
    @PrimaryKeyColumn(name = HistoryEntity.OTHER_USER_ID, ordinal = 1, type = PrimaryKeyType.PARTITIONED)
    @CassandraType(type = DataType.Name.UUID)
    private UUID otherUserId;
  
    @PrimaryKeyColumn(name = HistoryEntity.CREATED, ordinal = 2, type = PrimaryKeyType.CLUSTERED, ordering = Ordering.DESCENDING)
    private Date created;
  
  }


• Don't use Cassandra for all types of use cases. An RDMS still has its value, e.g for ACID requirements. Cassandra is eventually consistent.

Kubernetes

• See my diagram in this post.

Miscellaneous

• Use dig for DNS resolving problems


• Use pgAdmin III for PostgreSQL GUI


• To stop SonarQube complaining about unused private fields when using Lombok @Data annotation: add to each of those classes @SuppressWarnings("PMD.UnusedPrivateField")


• Managed to not need transactions nor XA transactions for message publishing, message reading, store db, message sending, by using the confirm + ack mechanism.
  And allow message to be read again. DB then sees: oh already stored (or do an upsert).
  So,when processing message from the queue:
  1- store in db
  2- send message on queue
  3- only then ack back to queue that read was successful


• Performance: instantiate the Jackson2 ObjectMapper once as static, not in each call, so:
  

  private static final ObjectMapper mapper = new ObjectMapper();

• Javascript: when an exception occurs in a callback and it is not handled, processing just ends. Promises have better error handling.


• clamd would not start correctly; it would try to start but then show 'Killed' when started via the commandline. Turns out it runs out of memory when starting up.  Though we had enough RAM (16G total, 3G free), it turns out clamd needs swap configured!


• Linux bash shell script to loop through projects for tagging with projects with spaces in their name:
  
  PROJECTS="
    project1
    project space2
  ";
  IFS=$'\n'
  for PROJECT in $PROJECTS
  do
    TRIM_LEADING_SPACE_PROJECT="$(echo -e "${PROJECT}" | sed -e 's/^[[:space:]]*//')"
    echo "Cloning '$TRIM_LEADING_SPACE_PROJECT'"
    git clone --depth=1 http://$USER:$GITPASSWD@github.com/projects/$TRIM_LEADING_SPACE_PROJECT.git
  done


• OpenVPN in Windows 10: Sometimes it hangs on "Connecting..."  It doesn't show the popup to enter username/pwd. Go to View logs. Then when you see: Enter management password in the logs: ???? you have to kill the OpenVPN Daemon under Processes tab (windows taskmanager). The service is stopped when exiting the app but that's not enough!


• javascript/nodejs log every call that comes in:
  
  app.use(function (req, res, next) {
    console.log('Incoming request = ' + new Date(), req.method, req.url);
    logger.debug('log at debug level');
    next()
  }


• If ever your mouse is suddenly not working anymore your VirtualBox guest, kill the process in your guest-machine mentioned in comment 5 here. After that the mouse works again in your vbox guest.


• Fix Firefox to version 45.0.0 for selenium driver tests:
  
  sudo apt-get install -y firefox=45.0.2+build1-0ubuntu1
  sudo apt-mark hold firefox


• Setting the cookie attribute Secure (indicating cookie should only be sent over httpS) can be seen when using curl to request the URL(s) that should send that cookie plus the new attribute, even when using HTTP. See also my previous post.
  
  But when using a browser and HTTP, you probably won't see the secure cookie appear in the cookie store. This is (probably) because the browser knows not to store it in that case because it's HTTP being used.


• Idempotency within services is key for resilience and be able to resend an event or perform an API call again.