The epic  groups the issues submitted about a new feature request that revolves around exposing from the the synapse API some basic statistics about projects. In the following the list of relevant tickets in the epic:

Introduction

It is clear that there is the need for the platform to provide some statistics about the usage of the data within synapse: discussions around various aspects and statistics to gather and expose have been going on for several years.

There are different statistics that the synapse projects owner and administrators are currently interested in and different levels of understanding of what should be exposed by the API. In particular there are 3 main points of discussion that are related but need clarifications:

1. Downloads Count
2. Page Views
3. Data Breaches/Audit Trail

Downloads Count

This is the main statistic that the users are currently looking for, it provides a way for project owners, funders and data contributor to monitor the interest over time in the datasets published in a particular project, which then reflects on the interest on the project itself and it is a metric of the value provided by the data in the project. This kind of data is related specifically to the usage of the platform by synapse users, since without being authenticated the downloads are not available. This is part of a generic category of statistics that relates to the entities and metadata that is stored in the backend and it's only a subset of aggregate statistic that can be exposed (e.g. number of projects, users, teams etc).

Page Views

This metric is also an indicator to monitor the interest but it plays a different role and focuses on the general user activity over the synapse platform as a whole. While it might be an indicator for a specific project success it captures a different aspect that might span to different type of clients used to interface on the Synapse API and that include information about users that are not authenticated into synapse. For this particular aspect there are tools already integrated (E.g. google analytics) that collect analytics on the user interactions. Note however that this information is not currently available to the synapse users, nor setup in a way to produce information about specific projects pages, files, wikis etc.

Data Breaches/Audit Trail

Another aspect that came out and might seem related is the identification of when/what/why of potential data breaches (e.g. a dataset was released even though it was not supposed to). This relates to the audit trail of users activity in order to identify potential offenders. While this information is crucial it should not be exposed by the API, and a due process is in place in order to access this kind of data.

Project Statistics

With this brief introduction in mind this document focuses on the main driving use case, that is:

• A funder and/or project creator would like to have a way to understand if the project is successful and if its data is used.

There are several metrics that can be used in order to determine the usage and success of a project, among which:

• Project Access (e.g. page views)
• Number of Downloads
• Number of Uploads
• User Discussions

Current Situation

Currently the statistics about a project are collected in various ways mostly through the Data Warehouse, using /wiki/spaces/DW/pages/796819457 of the data collected to run ad-hoc queries for aggregations as well as through dedicated clients (See Synapse Usage Report).

First Phase Proposal

In a first phase we want to have a minimal set of statistics that are exposed from the synapse platform API that provides a way to fulfill the use case. In particular we identified the following aspects that allows to have an initial implementation that can be extended in a later moment if needed:

• Expose statistics about number of download and number of uploads
• Expose statistics about the number of unique users that downloaded and/or uploaded
• Statistics are collected on a per project basis (no file level statistics)
• Statistics limited to the last 12 months
• Statistics aggregated monthly (no total downloads or total users)
• Statistics access is restricted through a new ACCESS_TYPE VIEW_STATISTICS, initially granted to project owners and administrators
• No run-time filtering

Files, Downloads and Uploads

Files in synapse are referenced through an abstraction (FileHandle) that maintain the information about the link to the content of the file itself (e.g. an S3 bucket). A file handle is then referenced in many places (such as FileEntity and WikiPage, see FileHandleAssociateType) as pointers to the actual file content. In order to actually download the content the synapse platform allows to generated a pre-signed url (according to the location where the file is stored) that can be used to directly download the file. Note that the platform has no way to guarantee that the pre-signed url is actually used by the client in order to download a file. Every single pre-signed url request in the codebase comes down to a single method getURLForFileHandle.

In the context of a project we are interested in particular to download (and/or uploads) of entities of type FileEntity and TableEntity (See What is a "download" in Synpase?) and the download request made for the associated file handles.

There are also different ways to actually get pre-signed urls for file handles that are exposed through the API. For the context of project and files download we are interested in specific operations, in particular there are several API endpoints that are used to request a pre-signed url to download the content of entities of type FileEntity (For a complete list of endpoints that reference file handles see Batch FileHandle and File URL Services):

The main aspect that we want to capture is that in general any relevant file download should include the triplet associateObjectType, associateObjectId and fileHandleId (See the FileHandleAssociation) that allows us to understand the source of the file download in the context of a request.

In the following we provide some basic download statistics computed for the last 30 days worth of data (as of 06/27/2019) as reported by the data warehouse:

"direct" downloads statistics

"Batch and bulk" Downloads

Proposed API Design

The current API design uses a polymorphic approach to access certain kind of objects, in particular related to Projects, Folders and Files (See Entities, Files, and Folders Oh My!), exposing a single prefixed endpoint for CRUD operations (/entity). This has the effect that a GET request to the /entity/{id} endpoint for a specific entity might return a different response type (See the Entity Response Object). For a first implementation we would need an endpoint to expose statistics about a project.

In general computing statistics might be an expensive operation, moreover in the future we might want to extend the API to include several different types of statistics. For the current use case we can potentially pre-compute statistics aggregates monthly for the projects so that we can serve them relatively quickly with a single lookup. While we cannot guarantee that all kind of statistics that will be exposed in the future can be pre-computed and will return within a reasonable response time to ease the clients integration we propose to have a dedicated endpoint that will return the statistics for a project within a single synchronous HTTP call.

If in the future we require more complex and/or expensive computation for certain statistics we can extend the API to integrate with the /asynchronous/job API (See Asynchronous Job API) in order to offload the computation to a background worker.

Endpoints

We propose to introduce a dedicated /statistics endpoint that will serve as main entry point to statistics requests. The project statistics are nested within this endpoint:

 The endpoint accepts the following optional URL parameters:

GET /statistics/project/syn123?downloads=true&uploads=false

Response Objects

ProjectStatistics

Represents the response for the project statistics request:

DownloadStatistics/UploadStatistics

StatisticsCountBucket

The purpose of this object is to include information about the count of a certain metric within a specific time frame (in this case monthly):

{
	"lastUpdatedOn: "2019-26-06T01:01:00.000Z",
	"downloads": {
		"lastUpdatedOn": "2019-26-06T01:01:00.000Z",
		"monthly": [{
			"startDate": "2019-01-06T00:00:00.000Z", 
			"count": 1230,
			"usersCount": 10
		},
		{
			"startDate": "2019-01-05T00:00:00.000Z", 
			"count": 10000,
			"usersCount": 100
		}]
	},
	"uploads": {
		"lastUpdatedOn": "2019-26-06T01:01:00.000Z",
		"monthly": [{
			"startDate": "2019-01-06T00:00:00.000Z", 
			"count": 51200,
			"usersCount": 200
		},
		{
			"startDate": "2019-01-05T00:00:00.000Z", 
			"count": 10000,
			"usersCount": 100
		}]
	}
}

Proposed Backend Architecture

In order to serve the statistics from the synapse API we need a way to efficiently access the statistics without heavy loading the web instances of the API.

Kinesis Firehose

The idea is to use Kinesis Firehose to send the events we are interested in (e.g. file upload and file download) as json records, the kinesis stream will funnel the records to firehose that will be converted to the columnar format Apache Parquet (the table schema is created and managed in AWS glue) and stored to an S3 bucket.

For the first phase we collect statistics for download and uploads, for each type of event we will have a separate stream, an example of JSON object sent to the kinesis stream for a download event:

{
    "timestamp": "1562626674712",
    "stack": "dev",
    "instance": 123,
    "projectId": 456,
    "userId": 5432,
    "associationType": "FileEntity",
    "associationId": 12312
    "fileId": 6789
}

Athena

Once the data is in S3 it can be queried with AWS Athena with standard SQL. For the JSON schema example above we can run an SQL query grouping for example by projectId (and filtering by timestamp) and counting the records as well as the distinct users (Note: Athena uses Presto as query engine, that supports approximate aggregations such as approx_distinct).

Athena can be accessed using the Amazon SDK directly in Java. This allows us to implement synapse background workers that periodically queries the data using Athena in order to compute and store manageable aggregates that can be queried directly from the synapse services.

Given that we will query the data stored in S3 month by month, we can partition the data directly so that Athena will scan only the needed records (See https://docs.aws.amazon.com/athena/latest/ug/partitions.html). We can initially create partitions day by day so that we do not restrict ourselves to always load a month of data for each query that we run using athena, this will produce slightly slower queries for the worker as multiple partitions will need to be loaded, but will gives us more flexibility.

Statistics Tables

In a first phase we only provide monthly aggregates per project to the client, to this end we can store the monthly aggregates into RDS using dedicated statistics tables. If we need to store more fine grained statistics (e.g. daily, or at the file level) we can move in a later moment to a more scalable solution (e.g. DynamoDB seems a good fit).

In order to compute the monthly aggregates we want to make sure that the workers only queries the current month (unless the last successful run was past the current month). For each type of statistics we store the timestamp of the last successful run into a dedicated table statistics_status:

The workers will query this table in order to get the months for which the aggregates needs to be performed (Note that each time a worker runs the query will need to scan all the data for each considered month as we need to get estimates on the number of unique users that downloaded/uploaded files on a monthly basis).

The monthly aggregates for each project is then stored into a dedicated table statistics_project_monthly:

The table contains for each project, year and month the count of downloads, uploads, the number of unique users that downloaded and uploaded files as well as the last time the statistic for that particular month was updated (per download and upload). This table can be queried directly by the service layer in the synapse API in read only.

Statistics Workers

We will initially need at least two different workers that will aggregate the statistics periodically using the Athena SDK:

• DownloadStatisticsAggregator: Will run every X hours (configurable, but probably 6 to 12 hours should be enough), run the SQL query on the S3 data for the downloads streams for the current month (or previous months according to the statitistics_status last_update value) and update the statistics_project_monthly table above.
• UploadStatisticsAggregator: Similar to the DownloadStatitisticsAggregator will perform the aggregation for uploads, updating the statistics_project_monthly table

Both the workers will need to batch the query result into a smaller set, potentially running multiple transactions to save the data.

This initial setup will allow us to serve the statistics for a given project, but poses some potential issues:

• Zero downloads/uploads problem: We can avoid storing unnecessary data for each project if for a given month there were no uploads or downloads, at the application level we can simply return a 0 count if the record is not in the table for a given month. This poses a problem since we cannot discriminate between a zero count or a "not yet computed" case. We can work around this by using the global last_update. if for a given project we never have downloads or uploads but we know that we last updated recently we can assume that we had no downloads or uploads in the past.
• Last update time: The last update time for a given statistics (download and/or upload) is valid only if the project has had in the last month at least one download or one upload. We can use the global last_update for the given statistics from the statistics_status table instead, but it's still an approximation: updating the statistics table might take some time, multiple transactions are potentially needed and even though the statistics for a given project can be retrieved the last_might not reflect the fact that the worker is still in progress.

The issues above might not be considered critical, as statistics are anyway used as an indication and not taken strictly. We could potentially solve both problems implementing a stricter synchronization of projects and statistics with a set of additional workers:

• MonthlyStatisticsInitializer: The worker would need to run at the beginning of each month (or run periodically with a saved state) to pre-populate the statistics_project_monthly table for each project for the current month with a 0 count and no last_update. This would allow the previous workers to perform only updates on the project ids that they gathered from the aggregation.
• NewProjectListener: The previous worker alone is not enough as new projects are created, the purpose of this worker would be to poll the appropriate SQS queue for new projects and initialize the record for the current month to 0 in the  statistics_project_monthly table.

Additionally we might want to store in the statistics_status table the initial date when we started collecting statistics, this would allow us to truncate the months past that date so that we can report an "unknown" status to the client.

Web Client Integration

The web client should have a way to show the statistics for a project or a specific file, some initial ideas:

• Have a dedicated menu item that leads to a statistics dashboard (should be visible only to the project owner/administrator)