Initial import: links posts + github knowledge

github-knowledge/application.md

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+---
+title: Application
+created: 2019-05-13
+updated: 2019-05-13
+type: summary
+tags: [tech, reference]
+external: https://github.com/wahyd4/knowledge/blob/master/categories/application.md
+---
+
+# Search
+
+- ElasticSearch
+	- Logstash
+	- Kibana
+
+# APM
+
+## Newrelic
+
+The famous APM service provider, it support multiple languages, it requires you install agent to the application.
+## Datadog
+
+Another alternative APM service provider
+## Pinpoint
+
+The Java based open source APM.
+
+# Ping check service
+
+## Pingdom
+It's a online web services, it gives you ability to do ping to your website from different regions, web servers.
+
+# Monitoring
+
+## Bosun
+
+## Prometheus
+
+### Prometheus Metric types
+
+* Counter, A counter is a cumulative metric that represents a single monotonically increasing counter whose value can only increase or be reset to zero on restart. For example, you can use a counter to represent the number of requests served, tasks completed, or errors. Do not use a counter to expose a value that can decrease.
+* A gauge is a metric that represents a single numerical value that can arbitrarily go up and down.
+Gauges are typically used for measured values like temperatures or current memory usage, but also "counts" that can go up and down, like the number of running goroutines.
+* A histogram samples observations (usually things like request durations or response sizes) and counts them in configurable buckets. It also provides a sum of all observed values.
+* Summary, Similar to a histogram, a summary samples observations (usually things like request durations and response sizes). While it also provides a total count of observations and a sum of all observed values, it calculates configurable quantiles over a sliding time window.
+
+
+# API
+
+## RPC(remote procedure call)
+	- disadvantages
+		- coupling
+		- clients needs to know the request procedure names
+	- advantages
+		- more freedoms to define any requests.
+	- examples: <https://api.slack.com/methods>
+
+## Restful /Representational State Transfer
+	- Easy to cache
+	- every url represent a resource
+	- disadvantages some special method is hard to use restful to name it. like /login, /resetpassword
+	- examples [https://developer.github.com/v3/](https://developer.github.com/v3/)
+	- methods
+		- GET
+		- POST
+		- PUT
+        - DELETE
+
+## GraphQL
+
+ It Can allows you to define fields you want to have.
+
+## gRPC
+	- protocol buffers
+
+```go
+    // The greeter service definition.
+    service Greeter {
+        // Sends a greeting
+        rpc SayHello (HelloRequest) returns (HelloReply) {}
+    }
+    // The request message containing the user's name.
+    message HelloRequest {
+        string name = 1;
+    }
+    // The response message containing the greetings
+    message HelloReply {
+        string message = 1;
+    }
+```
+	- A opensource  remote procedure call framework based on HTTP2 and protobuf
+	- advantages
+		- baed on HTTP2, better performance
+		- call remote like local method, and support multiple language
+		- protobuf serialization and deserialization is faster than JSON
+
+## JSON-RPC
+
+It's a little bit similar with gRPC one, but you define the action method in the JSON request body.
+
+POST /api
+```json
+{
+    "jsonrpc": "2.0",
+    "method": "subtract",
+    "params": [42, 23],
+    "id": 1
+}
+```
+Links:
+* JSON-RPC specification: <http://www.jsonrpc.org/specification>
+* O API - an alternative to REST APIs
+: <https://hackernoon.com/o-api-an-alternative-to-rest-apis-e9a2ed53b93c>
+
+## Open API
+
+The OpenAPI Specification (OAS) defines a standard, programming language-agnostic interface description for REST APIs, which allows both humans and computers to discover and understand the capabilities of a service without requiring access to source code, additional documentation, or inspection of network traffic. When properly defined via OpenAPI, a consumer can understand and interact with the remote service with a minimal amount of implementation logic. Similar to what interface descriptions have done for lower-level programming, the OpenAPI Specification removes guesswork in calling a service. Open API can be described in `yaml` or `json`
+
+### Use cases
+
+* Interactive documentation
+* Mock server generation
+* Client code generation
+* Automation testing
+
+### Implementation
+
+* [Swagger](http://swagger.io)
+
+### Tools
+
+[Redoc](https://github.com/Rebilly/ReDoc) OpenAPI/Swagger-generated API Reference Documentation, which gives you beautiful interface to the API spec file.
+
+`redoc-cli` is a command line tool to generate a single HTML version of API Spec file.
+
+```bash
+redoc-cli bundle swagger.json
+```
+Some sample swagger files: <http://rackerlabs.github.io/wadl2swagger/openstack.html>
+
+## Versioning
+
+### Proper define the version of your application
+
+According to [semver](https://semver.org/), the following is the general guideline.
+
+> Given a version number MAJOR.MINOR.PATCH, increment the:
+>
+> 1. MAJOR version when you make incompatible API changes,
+> 2. MINOR version when you add functionality in a backwards-compatible manner, and
+> 3. PATCH version when you make backwards-compatible bug fixes.
+> Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.
+
+# Log and Error
+
+## Sentry
+
+Within Sentry, you can view all your errors, and also do filtering and grouping things.
+
+## ELK
+
+Elasticsearch + Logstash + Kibana