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Spring Cloud - "Umbrella Project" which consists of multiple frameworks

• Spring Cloud Connectors - Connectors to PAAS services to scale new nodes
  • Heroku
  • Cloud Foundry
• Spring Cloud Bus - Event Bus (message queue)
• Spring Cloud Netflix (= Spring Cloud Netflix Stack) - The central part of the application consists of multiple components (Provided by Netflix)
  • Archaius - Centalized configuration (like Spring Cloud Config but with Netflix technology)
  • Zuul - Proxy server with virtual paths each pointing to a specifc service which can be executed in multiple instances: Central Path Configuration so that the user doesn't recognize changes
• Hystrix - Resilience Framework (Used with Ribbon + Feign where Hystrix is the core): A Switch that points to another instance (or throws an error when no other instance is available) when the requested instance throws an error and pauses requests to the requested instance for an amount of time (prevents deadlocks or unlimited

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-- Current Date as Timestamp
CURRENT_TIMESTAMP

-- Current Date as Date
SYSDATE

-- Insert multiple rows
insert into countries select rownum, 'Name'||rownum from dual connect by rownum <= 1000000;

-- Delete all rows from a table

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# Show a preview of the selected method/class: "Quick Definition Lookup"
Ctrl + Shift + I

# Switch to another open tab
Ctrl + Tab

# Close a specific tab within this Switcher (Ctrl + Tab)
Choose tab in Switcher > Backspace or Delete

# Evaluate Expression (in a dialog)

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DockerEE Basic - 80 Euro pro Maschine

Storage Driver

• Debian (Default): AUFS
• CentOS (Default): Device Mapper

Docker Datacenter

• Build Pipeline
• Zugriffskontrolle

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User Space vs. Kernel Space

• User Space = User + Prozesse + Libraries
• Kernel Space = Kernel + Driver + Hardware
• API through System Calls and Signals provided by glibc (C Library)

System Call vs. Signal

• System Call = API call from a program to the kernel
• Signal = An Event like SIGTERM or SIGKILL that interrupts the programs control flow

Static linked vs. Dynamically linked

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Glossar

• Sidecar - Process that encapsulates required technologies (e.g. logging, monitoring, service discovery, etc.) in the microservices environment and makes them available to microservices that are not able to use those technologies natively
• Immutable Server -

Configuration + Coordination

• Zookeeper - https://zookeeper.apache.org/ - Provides configs in a hierarchical key-value store that is replicated and synchronized across large distributed systems.
• etcd - https://github.com/coreos/etcd - Like Zookeeper. Distributed reliable key-value store for the most critical data of a distributed system. Provides a REST API. It is possible to do locking in a distributed system with it.
• Spring Cloud Config - Provides a REST API. Config files can be based in a Git repo. The config data can be encrypted (e.g. for passwords in config files)

Service Discovery

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REST API Cheatsheet

Source: https://www.youtube.com/watch?v=5WXYw4J4QOU

• POST, GET, PUT, DELETE != CRUD
• no verbs -> just nouns for Resources: /applications or /applications/123
• Possible Responses: Collection of Resources (e.g. with Links) or One instance of a Resource
• Keep your API course grained to be scaleble to future requirements
• For Resources: Be as specific as possible: /customers vs. /newsletter-customers and /registered-customers
• PUT for Create: Can be used when the Client has the ability to create an identifier for the Resource himself. But it has to contain a full replacement of the dataset: PUT /applications/123

staticpix

REST API Cheatsheet

Source: https://www.youtube.com/watch?v=5WXYw4J4QOU

• POST, GET, PUT, DELETE != CRUD
• no verbs -> just nouns for Resources: /applications or /applications/123
• Possible Responses: Collection of Resources (e.g. with Links) or One instance of a Resource
• Keep your API course grained to be scaleble to future requirements
• For Resources: Be as specific as possible: /customers vs. /newsletter-customers and /registered-customers
• PUT for Create: Can be used when the Client has the ability to create an identifier for the Resource himself. But it has to contain a full replacement of the dataset: PUT /applications/123

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Maven Cheatsheet

Show unused dependencies

mvn dependency:analyze

Show infos to one specific plugin (available goals with phases, etc.)

mvn help:describe -Dplugin=org.sonarsource.scanner.maven:sonar-maven-plugin -Ddetail