Nebula

A libp2p DHT crawler and monitor that tracks the liveness of peers. The crawler connects to DHT bootstrap peers and then recursively follows all entries in their k-buckets until all peers have been visited. The crawler supports the IPFS, Filecoin, Polkadot, Kusama, Rococo, Westend networks and more.

The crawler was:

• 🏆 awarded a prize in the DI2F Workshop hackathon. 🏆
• 🎓 used for the ACM SigCOMM'22 paper Design and Evaluation of IPFS: A Storage Layer for the Decentralized Web 🎓

📊 We publish weekly reports based on the crawl results here! 📊

Table of Contents

• Table of Contents
• Project Status
• Usage
• Install
  • From source
• How does it work?
  • crawl
  • monitor
  • resolve
• Development
  • Database
  • Tests
• Report
• Related Efforts
• Maintainers
• Contributing
• Support
• Other Projects
• License

Project Status

The crawler is used for a couple of academic project, and I'm running it since July '21 continuously.

The gathered numbers about the IPFS network are in line with existing data like from the wiberlin/ipfs-crawler. Their crawler also powers a dashboard which can be found here.

Install

From source

To compile it yourself run:

go install github.com/dennis-tra/nebula-crawler/cmd/nebula@latest # Go 1.19 or higher is required (may work with a lower version too)

Make sure the $GOPATH/bin is in your PATH variable to access the installed nebula executable.

Usage

Nebula is a command line tool and provides the crawl sub-command. To simply crawl the IPFS network run:

nebula crawl --dry-run

The crawler can store its results as JSON documents or in a postgres database - the --dry-run flag prevents it from doing either. Nebula will print a summary of the crawl at the end instead. A crawl takes ~5-10 min depending on your internet connection. You can also specify the network you want to crawl by appending, e.g., --network FILECOIN and limit the number of peers to crawl by providing the --limit flag with the value of, e.g., 1000. Example:

nebula crawl --dry-run --network FILECOIN --limit 1000

To store crawl results as JSON files provide the --json-out command line flag like so:

nebula crawl --json-out ./results/

After the crawl has finished, you will find the JSON files in the ./results/ subdirectory.

When providing only the --json-out command line flag you will see that the *_neighbors.json document is empty. This document would contain the full routing table information of each peer in the network which is quite a bit of data (~250MB as of April '23) and is therefore disabled by default. To populate the document you'll need to pass the --neighbors flag to the crawl subcommand.

nebula crawl --neighbors --json-out ./results/

The routing table information forms a graph and graph visualization tools often operate with adjacency lists. To convert the *_neighbors.json document to an adjacency list, you can use jq and the following command:

jq -r '.NeighborIDs[] as $neighbor | [.PeerID, $neighbor] | @csv' ./results/2023-04-16T14:32_neighbors.json > ./results/2023-04-16T14:32_neighbors.csv

There are a few more command line flags that are documented when you run nebula crawl --help.

When Nebula is configured to store its results in a postgres database (see below), then it also tracks session information of remote peers.

How does it work?

crawl

The crawl sub-command starts by connecting to a set of bootstrap nodes and constructing the routing tables (kademlia k-buckets) of these peers based on their PeerIDs. Then nebula builds random PeerIDs with common prefix lengths (CPL) that fall each peers buckets, and asks each remote peer if they know any peers that are closer (XOR distance) to the ones nebula just constructed. This will effectively yield a list of all PeerIDs that a peer has in its routing table. The process repeats for all found peers until nebula does not find any new PeerIDs.

This process is heavily inspired by the basic-crawler in libp2p/go-libp2p-kad-dht from @aschmahmann.

If Nebula is configured to store its results in a database, every peer that was visited is persisted in it. The visit information includes latency measurements (dial/connect/crawl durations), current set of multi addresses, current agent version and current set of supported protocols. If the peer was dialable nebula will also create a session instance that contains the following information:

CREATE TABLE sessions (
    -- A unique id that identifies this particular session
    id                      INT GENERATED ALWAYS AS IDENTITY,
    -- Reference to the remote peer ID. (database internal ID)
    peer_id                 INT           NOT NULL,
    -- Timestamp of the first time we were able to visit that peer.
    first_successful_visit  TIMESTAMPTZ   NOT NULL,
    -- Timestamp of the last time we were able to visit that peer.
    last_successful_visit   TIMESTAMPTZ   NOT NULL,
    -- Timestamp when we should start visiting this peer again.
    next_visit_due_at       TIMESTAMPTZ,
    -- When did we notice that this peer is not reachable.
    first_failed_visit      TIMESTAMPTZ,
    -- When did we first notice that this peer is not reachable anymore.
    last_failed_visit       TIMESTAMPTZ,
    -- When did we last visit this peer. For indexing purposes.
    last_visited_at         TIMESTAMPTZ   NOT NULL,
    -- When was this session instance updated the last time
    updated_at              TIMESTAMPTZ   NOT NULL,
    -- When was this session instance created
    created_at              TIMESTAMPTZ   NOT NULL,
    -- Number of successful visits in this session.
    successful_visits_count INTEGER       NOT NULL,
    -- The number of times this session went from pending to open again.
    recovered_count         INTEGER       NOT NULL,
    -- The state this session is in (open, pending, closed)
    -- open: currently considered online
    -- pending: peer missed a dial and is pending to be closed
    -- closed: peer is considered to be offline and session is complete
    state                   session_state NOT NULL,
    -- Number of failed visits before closing this session.
    failed_visits_count     SMALLINT      NOT NULL,
    -- What's the first error before we close this session.
    finish_reason           net_error,
    -- The uptime time range for this session measured from first- to last_successful_visit to
    uptime                  TSTZRANGE     NOT NULL,

    -- The peer ID should always point to an existing peer in the DB
    CONSTRAINT fk_sessions_peer_id FOREIGN KEY (peer_id) REFERENCES peers (id) ON DELETE CASCADE,

    PRIMARY KEY (id, state, last_visited_at)

) PARTITION BY LIST (state);

At the end of each crawl nebula persists general statistics about the crawl like the total duration, dialable peers, encountered errors, agent versions etc...

Info: You can use the crawl sub-command with the --dry-run option that skips any database operations.

Command line help page:

NAME:
   nebula crawl - Crawls the entire network starting with a set of bootstrap nodes.

USAGE:
   nebula crawl [command options] [arguments...]

OPTIONS:
   --bootstrap-peers value [ --bootstrap-peers value ]  Comma separated list of multi addresses of bootstrap peers (default: default IPFS) [$NEBULA_CRAWL_BOOTSTRAP_PEERS, $NEBULA_BOOTSTRAP_PEERS]
   --protocols value [ --protocols value ]              Comma separated list of protocols that this crawler should look for [$NEBULA_CRAWL_PROTOCOLS, $NEBULA_PROTOCOLS]
   --workers value                                      How many concurrent workers should dial and crawl peers. (default: 1000) [$NEBULA_CRAWL_WORKER_COUNT]
   --limit value                                        Only crawl the specified amount of peers (0 for unlimited) (default: 0) [$NEBULA_CRAWL_PEER_LIMIT]
   --dry-run                                            Don't persist anything (default: false) [$NEBULA_CRAWL_DRY_RUN]
   --json-out DIR                                       If set, stores the crawl results as JSON documents at DIR (takes precedence over database settings). [$NEBULA_CRAWL_JSON_OUT]
   --neighbors                                          Whether to persist all k-bucket entries of a particular peer at the end of a crawl. (default: false) [$NEBULA_CRAWL_NEIGHBORS]
   --check-exposed                                      Whether to check if the Kubo API is exposed. Checking also includes crawling the API. (default: false) [$NEBULA_CRAWL_CHECK_EXPOSED]
   --network value                                      Which network should be crawled (IPFS, FILECOIN, KUSAMA, POLKADOT). Presets default bootstrap peers and protocol. (default: "IPFS") [$NEBULA_CRAWL_NETWORK]
   --help, -h                                           show help

monitor

The monitor sub-command polls every 10 seconds all sessions from the database (see above) that are due to be dialed in the next 10 seconds (based on the next_visit_due_at timestamp). It attempts to dial all peers using previously saved multi-addresses and updates their session instances accordingly if they're dialable or not.

The next_visit_due_at timestamp is calculated based on the uptime that nebula has observed for that given peer. If the peer is up for a long time nebula assumes that it stays up and thus decreases the dial frequency aka. sets the next_visit_due_at timestamp to a time further in the future.

Command line help page:

NAME:
   nebula monitor - Monitors the network by periodically dialing previously crawled peers.

USAGE:
   nebula monitor [command options] [arguments...]

OPTIONS:
   --workers value  How many concurrent workers should dial peers. (default: 1000) [$NEBULA_MONITOR_WORKER_COUNT]
   --help, -h       show help

resolve

The resolve sub-command goes through all multi addresses that are present in the database and resolves them to their respective IP-addresses. Behind one multi address can be multiple IP addresses due to, e.g., the dnsaddr protocol. Further, it queries the GeoLite2 database from Maxmind to extract country information about the IP addresses and UdgerDB to detect datacenters. The command saves all information alongside the resolved addresses.

Command line help page:

NAME:
   nebula resolve - Resolves all multi addresses to their IP addresses and geo location information

USAGE:
   nebula resolve [command options] [arguments...]

OPTIONS:
   --udger-db value    Location of the Udger database v3 [$NEBULA_RESOLVE_UDGER_DB]
   --batch-size value  How many database entries should be fetched at each iteration (default: 100) [$NEBULA_RESOLVE_BATCH_SIZE]
   --help, -h          show help (default: false)

Development

To develop this project you need Go > 1.16 and the following tools:

• golang-migrate/migrate to manage the SQL migration v4.15.2
• volatiletech/sqlboiler to generate Go ORM v4.14.2
• docker to run a local postgres instance

To install the necessary tools you can run make tools. This will use the go install command to download and install the tools into your $GOPATH/bin directory. So make sure you have it in your $PATH environment variable.

Database

You need a running postgres instance to persist and/or read the crawl results. Run make database or use the following command to start a local instance of postgres:

docker run --rm -p 5432:5432 -e POSTGRES_PASSWORD=password -e POSTGRES_USER=nebula -e POSTGRES_DB=nebula postgres:14

Info: You can use the crawl sub-command with the --dry-run option that skips any database operations or store the results as JSON files with the --json-out flag.

The default database settings are:

Name     = "nebula",
Password = "password",
User     = "nebula",
Host     = "localhost",
Port     = 5432,

Migrations are applied automatically when nebula starts and successfully establishes a database connection.

To run them manually you can run:

# Up migrations
make migrate-up # runs: migrate -database 'postgres://nebula:password@localhost:5432/nebula?sslmode=disable' -path migrations up

# Down migrations
make migrate-down # runs: migrate -database 'postgres://nebula:password@localhost:5432/nebula?sslmode=disable' -path migrations down

# Generate the ORM with SQLBoiler
make models # runs: sqlboiler
# This will update all files in the `pkg/models` directory.

# Create new migration
migrate create -ext sql -dir pkg/db/migrations -seq some_migration_name

Tests

To run the tests you need a running test database instance:

make database-test
go test ./...

Report

There is a top-level report folder that contains a script to generate a comprehensive data report.

Related Efforts

• wiberlin/ipfs-crawler - A crawler for the IPFS network, code for their paper (arXiv).
• adlrocha/go-libp2p-crawler - Simple tool to crawl libp2p networks resources
• libp2p/go-libp2p-kad-dht - Basic crawler for the Kademlia DHT implementation on go-libp2p.

Maintainers

@dennis-tra.

Contributing

Feel free to dive in! Open an issue or submit PRs.

Support

It would really make my day if you supported this project through Buy Me A Coffee.

Other Projects

You may be interested in one of my other projects:

• pcp - Command line peer-to-peer data transfer tool based on libp2p.
• image-stego - A novel way to image manipulation detection. Steganography-based image integrity - Merkle tree nodes embedded into image chunks so that each chunk's integrity can be verified on its own.
• antares - A gateway and pinning service probing tool.

License

Apache License Version 2.0 © Dennis Trautwein