ipld-eth-server/documentation/composeAndExecute.md

composeAndExecute

The composeAndExecute command is used to compose and execute over an arbitrary set of custom transformers. This is accomplished by generating a Go pluggin which allows the vulcanizedb binary to link to external transformers, so long as they abide by one of the standard interfaces.

Additionally, there are separate compose and execute commands to allow pre-building and linking to a pre-built .so file.

NOTE:

1. It is necessary that the .so file was built with the same exact dependencies that are present in the execution environment, i.e. we need to compose and execute the plugin .so file with the same exact version of vulcanizeDB.
2. The plugin migrations are run during the plugin's composition. As such, if execute is used to run a prebuilt .so in a different environment than the one it was composed in then the migrations for that plugin will first need to be manually ran against that environment's Postgres database.

These commands require Go 1.11+ and use Go plugins which only work on Unix-based systems. There is also an ongoing conflict between Go plugins and the use vendored dependencies which imposes certain limitations on how the plugins are built.

Commands

The compose and composeAndExecute commands assume you are in the vulcanizdb directory located at your system's $GOPATH, and that all of the transformer repositories for building the plugin are present at their $GOPATH directories.

The execute command does not require the plugin transformer dependencies be located in their $GOPATH directories, instead it expects a prebuilt .so file (of the name specified in the config file) to be in $GOPATH/src/github.com/vulcanize/vulcanizedb/plugins/ and, as noted above, also expects the plugin db migrations to have already been ran against the database.

compose:

./vulcanizedb compose --config=./environments/config_name.toml

execute:

./vulcanizedb execute --config=./environments/config_name.toml

composeAndExecute:

./vulcanizedb composeAndExecute --config=./environments/config_name.toml

Configuration

A .toml config file is specified when executing the commands. The config provides information for composing a set of transformers from external repositories:

[database]
    name     = "vulcanize_public"
    hostname = "localhost"
    user     = "vulcanize"
    password = "vulcanize"
    port     = 5432

[client]
    ipcPath  = "/Users/user/Library/Ethereum/geth.ipc"

[exporter]
    home     = "github.com/vulcanize/vulcanizedb"
    name     = "exampleTransformerExporter"
    save     = false
    transformerNames = [
        "transformer1",
        "transformer2",
        "transformer3",
        "transformer4",
    ]
    [exporter.transformer1]
        path = "path/to/transformer1"
        type = "eth_event"
        repository = "github.com/account/repo"
        migrations = "db/migrations"
        rank = "0"
    [exporter.transformer2]
        path = "path/to/transformer2"
        type = "eth_contract"
        repository = "github.com/account/repo"
        migrations = "db/migrations"
        rank = "0"
    [exporter.transformer3]
        path = "path/to/transformer3"
        type = "eth_event"
        repository = "github.com/account/repo"
        migrations = "db/migrations"
        rank = "0"
    [exporter.transformer4]
        path = "path/to/transformer4"
        type = "eth_storage"
        repository = "github.com/account2/repo2"
        migrations = "to/db/migrations"
        rank = "1"

• home is the name of the package you are building the plugin for, in most cases this is github.com/vulcanize/vulcanizedb
• name is the name used for the plugin files (.so and .go)
• save indicates whether or not the user wants to save the .go file instead of removing it after .so compilation. Sometimes useful for debugging/trouble-shooting purposes.
• transformerNames is the list of the names of the transformers we are composing together, so we know how to access their submaps in the exporter map
• exporter.<transformerName>s are the sub-mappings containing config info for the transformers
  • repository is the path for the repository which contains the transformer and its TransformerInitializer
  • path is the relative path from repository to the transformer's TransformerInitializer directory (initializer package).
    • Transformer repositories need to be cloned into the user's $GOPATH (go get)
  • type is the type of the transformer; indicating which type of watcher it works with (for now, there are only two options: eth_event and eth_storage)
    • eth_storage indicates the transformer works with the storage watcher that fetches state and storage diffs from an ETH node (instead of, for example, from IPFS)
    • eth_event indicates the transformer works with the event watcher that fetches event logs from an ETH node
    • eth_contract indicates the transformer works with the contract watcher that is made to work with contract_watcher pkg based transformers which work with either a light or full sync vDB to watch events and poll public methods (example1, example2)
  • migrations is the relative path from repository to the db migrations directory for the transformer
  • rank determines the order that migrations are ran, with lower ranked migrations running first
    • this is to help isolate any potential conflicts between transformer migrations
    • start at "0"
    • use strings
    • don't leave gaps
    • transformers with identical migrations/migration paths should share the same rank
• Note: If any of the imported transformers need additional config variables those need to be included as well

This information is used to write and build a Go plugin which exports the configured transformers. These transformers are loaded onto their specified watchers and executed.

Transformers of different types can be run together in the same command using a single config file or in separate instances using different config files

The general structure of a plugin .go file, and what we would see built with the above config is shown below

package main

import (
	interface1 "github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
	transformer1 "github.com/account/repo/path/to/transformer1"
	transformer2 "github.com/account/repo/path/to/transformer2"
	transformer3 "github.com/account/repo/path/to/transformer3"
	transformer4 "github.com/account2/repo2/path/to/transformer4"
)

type exporter string

var Exporter exporter

func (e exporter) Export() []interface1.EventTransformerInitializer, []interface1.StorageTransformerInitializer, []interface1.ContractTransformerInitializer {
	return []interface1.TransformerInitializer{
            transformer1.TransformerInitializer,
            transformer3.TransformerInitializer,
        },     []interface1.StorageTransformerInitializer{
            transformer4.StorageTransformerInitializer,
        },     []interface1.ContractTransformerInitializer{
            transformer2.TransformerInitializer,
        }
}