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Exchange is a suite of back-end services that handle bag ingest, restoration and deletion for APTrust, along with ingest, replication and restoration for DPN. Each of these services is in turn composed of a number of micro services that represent a single step in the overall process of a larger service. The micro services allow the larger services to recover from failure without having to re-do large amounts of work.

Exchange is a rewrite of APTrust's original bagman code, which is functionally complete, well tested and proven, but also messy and hard to maintain. Exchange aims to replace bagman with an equally complete system that meets the following criteria:

  • Code is divided into logical packages, is clear and easy to maintain and extend
  • Code relies on the fewest possible external systems (i.e. remove NSQ)
  • Code uses Amazon's Elastic File System, instead of EBS (i.g. remove volume manager)
  • Code provides a simple, extensible REST client (instead of the messy Fluctus client)
  • Code provides a straight-forward configuration system (currently a mess in bagman)
  • Code provides a simple, consistent context manager for both cron jobs an microservices (also a mess in bagman)
  • Code does not rely on any AWS services, other than S3 and Glacier

The first of these goals is the most important. The code must be clear and maintainable for the long term.

[Update: Oct. 16, 2019] 1700 commits after the last full-scale cleanup, the code is no longer clear or maintainable. Parts of it are downright offensive. It's needs a rewrite.

The existing bagman code will continue to run until this code is complete.

Dependency Mangement

Exchange uses Go modules. Go will automatically fetch and install modules when you run go test or go build.

You need Go 1.11 or later. Go 1.13 or later is preferred. If you're running a version before 1.13, you'll need to set the environment variable GO111MODULE=on.

To add or update a module, add/update the go.mod file, then run go mod tidy to add the module's dependencies.

Unit Testing

go test `go list ./... | grep -v integration`

or, if you have ruby installed

./scripts/test.rb units

Integration Testing

To run integration tests, you'll need the following:

  • A copy of the Pharos repo
  • Environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY set to values that can access APTrust's test buckets
  • Environment variables and PHAROS_API_KEY=c3958c7b09e40af1d065020484dafa9b2a35cea0
  • A copy of the develop branch of the dpn-server repo if you want to do DPN integration testing
  • A Postgres database (SQLite does not do well with the concurrent requests that the integration tests produce)
  • The Postgres user 'pharos' must own the pharos_integration database and must have the CREATEDB privilege.

Hints for correctly configuring the Postgres DB for integration tests:

grant all privileges on database pharos_integration to pharos; alter database pharos_integration owner to pharos; alter user pharos createdb;

Once you have all that, simply run ruby ./scripts/test.rb --help to see which integration tests are available and what they do. Note that integration tests are cumulative, with each test bringing the various services into the state that the next test needs to start. The three most common options for integration testing are:

  • ./scripts/ apt_fixity - This exercises all APTrust operations.
  • ./scripts/ dpn_ingest - This exercises most APTrust operations, along with DPN ingest. (Pushing items from APTrust into DPN.)
  • ./scripts/ apt_fixity - This exercises most APTrust operations, along with DPN replication. (Copying and storing items from other simulated DPN nodes.)

The integration tests may hang after the startup of the NSQ service if you killed a prior run of integration tests before they completed. Check your system using top, Task Manager, or Mac's Activity Monitor for stray ruby processes. Kill those processes and then try re-running the tests.

Setting up Postgres (required only for integration tests)

If you're on a Mac, get the Postgres app from

Open psql, either from a terminal, or if that doesn't work, from the Postgres Apps's elephant menu at the top of your screen. While you're up there, you might want to tell the Postgres app to always start on startup or login.

In the psql shell, run the following commands:

  1. create user pharos with password 'pharos';
  2. create database pharos_integration;
  3. grant all privileges on database pharos_integration to pharos;
  4. alter user pharos createdb;
  5. Change into the pharos repo directory and run RAILS_ENV=integration rake db:schema:load

That 4th command is required for integration tests because the test scripts drop and recreate the pharos_integration database at the start of the test cycle.

Building the Go applications and services

You can build all of the Go applications and services with this command:

ruby ./scripts/build.rb <path to output dir>

Note that some applications build differently for Windows. For example, apt_validate does not try to use mime magic when built for Windows. You can specify Windows, Mac, or Linux builds using go build tags, e.g.:

go build -tags="windows partners" apt_validate.go


Most of the TODOs are embedded in the code, and you can find them by running this command from the project's top-level directory:

grep -r TODO . --include=*.go --exclude=./vendor/*

The code in the /workers directory and in the /dpn/workers directory could use some cleanup. We added a number of logical tests and logging statements to that code after APTrust 2.0 went into production. In general, the fuctions in /workers and /dpn/workers should be broken up into shorter units, and some of it should be moved out into files and/or packages that can be unit-tested.

This is the list of global TODOs (not related to a specific package).

Aim for ~100% test coverage. Run the above test command with the -cover option to see coverage.


Exchange provides APTrust back-end services, including ingest, restoration, fixity checking and deletion.





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