Nerium 0.1.3

The little business intelligence engine that could

Nerium

A simple aiohttp microservice that submits queries to a database and returns machine-readable serialized results (typically JSON). By analogy with static site generators, Nerium reads its queries from local files, stored in a (configurable) directory on the filesystem. The idea is that report analysts should be able to author queries in their preferred local editor, and upload them where Nerium can use them.

OAO uses Nerium to easily and quickly provide JSON APIs with report results from our PostgreSQL data warehouse.

Nerium features an extendable architecture, allowing support for multiple query types and output formats by registering subclasses of ResultSet and ResultFormatter template classes.

Currently supports SQL queries using the excellent Records library. In keeping with Records usage, query parameters can be specified in key=value format, and (safely!) injected into your query in :key format.

In theory, ResultSet subclasses can be added (under contrib/resultset) for non-SQL query languages. This is a promising area for future development.

Default JSON output is an array of objects, one per result row, with database column names as keys. A compact JSON output format may also be requested, with separate column (array of column names) and data (array of row value arrays) nodes for compactness. Additional formats (not necessarily JSON) can be added by subclassing ResultFormatter.

In theory, Nerium can already support any backend that SQLAlchemy can, but since none of these are hard dependencies, drivers aren't included in Pipfile, and the Dockerfile only supports PostgreSQL. If you want Nerium to work with other databases, you can install Python connectors with pip, either in a virtualenv or by creating your own Dockerfile using FROM oaodev/nerium.

Nerium is inspired in roughly equal measure by SQueaLy and Pelican. It hopes to be something like Superset when it grows up.

Install/Run

Using Docker

$ docker run -d --name=nerium \
--envfile=.env \
-v /local/path/to/query_files:/app/query_files \
-p 8080:8080 oaodev/nerium

$ curl http://localhost:8081/v1/<query_name>?<params>

Local install

pipenv install nerium[pg]

Then add a query_files directory to your project, write your queries, and configure the app as described in the next section. The command nerium starts a local aiohttp server running the app, listening on port 8080.

Configuration

DATABASE_URL and optional QUERY_PATH (directory where query files reside, defaults to query_files in the working direcory) may be set in the environment, or in a local .env file.

In order to query multiple databases with a single instance of Nerium, create a subdirectory for each database under the $QUERY_PATH, place the related files under their respective directory, and include a separate .env file per subdirectory setting its DATABASE_URL value.

API

URLs

/v1/<string:query_name>/?[ne_format=<formatter>]&<query_params>

query_name should match the name of a given query script file, minus the file extension. Params are as specified in the queries themselves.

ne_format may be passed as in the query string as an optional formatter name, and defaults to 'default'. Other supported contrib options are described in Content section below.

Unknown values passed to query_extension or format will silently fall back to defaults.

Method

GET

Success Response

Code: 200

Content:
'default': [{<column_name>:<row_value>, etc..., }, {etc...}, ]
'compact': {"columns": [<list of column names>], "data": [<array of row value arrays>]}
'affix': {"error": false, "response": {<'default' array of result objects>}, "metadata":{"executed": <timestamp>, "params": {<array of name-value pairs submitted to query with request>}}}

Of course, it is possible that a database query might return no results. In this case, Nerium will respond with and empty JSON array [] regardless of specified format. This is not considered an error, and clients should be prepared to handle it appropriately.

Error Responses

Code: 400 Content: {"error": <exception.repr from Python>}

Sketchy Roadmap/TODOs

(in no particular order)

• Parameter discovery endpoint
• Report listing endpoint
• Plugin architecture
• Improve/mature plugin architecture
  • Separate base classes to a library
  • Implementation subclasses in contrib package
  • Subclass registration mechanism
• Configurable/flexible JSON output formatters (AffixFormatter could do with less hard-coding)
• Static output file generator (and other caching)
• Swagger docs
• Health check/default query endpoint (Own git commit hash report(?))