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fs-repo

Author(s):

Abstract

This spec defines fs-repo version 1, its formats, and semantics.

Table of Contents

Definition

fs-repo is a filesystem implementation of the IPFS repo.

Contents

.ipfs/
├── api             <--- running daemon api addr
├── blocks/         <--- objects stored directly on disk
│   └── aa          <--- prefix namespacing like git
│       └── aa      <--- N tiers
├── config          <--- config file (json or toml)
├── hooks/          <--- hook scripts
├── keystore/       <--- cryptographic keys
│   ├── key_b32name <--- private key with base32-encoded name
├── datastore/      <--- datastore
├── logs/           <--- 1 or more files (log rotate)
│   └── events.log  <--- can be tailed
├── repo.lock       <--- mutex for repo
└── version         <--- version file

api

./api is a file that exists to denote an API endpoint to listen to.

  • It MAY exist even if the endpoint is no longer live (i.e. it is a stale or left-over ./api file).

In the presence of an ./api file, ipfs tools (e.g. go-ipfs ipfs daemon) MUST attempt to delegate to the endpoint, and MAY remove the file if reasonably certain the file is stale. (e.g. endpoint is local, but no process is live)

The ./api file is used in conjunction with the repo.lock. Clients may opt to use the api service, or wait until the process holding repo.lock exits. The file's content is the api endpoint as a multiaddr

> cat .ipfs/api
/ip4/127.0.0.1/tcp/5001

Notes:

  • The API server must remove the api file before releasing the repo.lock.
  • It is not enough to use the config file, as the API addr of a daemon may have been overridden via ENV or flag.

api file for remote control

One use case of the api file is to have a repo directory like:

> tree $IPFS_PATH
/Users/jbenet/.ipfs
└── api

0 directories, 1 files

> cat $IPFS_PATH/api
/ip4/1.2.3.4/tcp/5001

In go-ipfs, this has the same effect as:

ipfs --api /ip4/1.2.3.4/tcp/5001 <cmd>

Meaning that it makes ipfs tools use an ipfs node at the given endpoint, instead of the local directory as a repo.

In this use case, the rest of the $IPFS_PATH may be completely empty, and no other information is necessary. It cannot be said it is a repo per-se. (TODO: come up with a good name for this).

blocks/

The block/ component contains the raw data representing all IPFS objects stored locally, whether pinned or cached. This component is controlled by the datastore. For example, it may be stored within a leveldb instance in datastore/, or it may be stored entirely with independent files, like git.

In the default case, the user uses fs-datastore for all /blocks so the objects are stored in individual files. In other cases, /blocks may even be stored remotely

config

The config file is a JSON or TOML file that contains the tree of configuration variables. It MUST only be changed while holding the repo.lock, or potentially lose edits.

hooks/

The hooks directory contains executable scripts to be called on specific events to alter ipfs node behavior.

Currently available hooks:

none

keystore/

The keystore directory holds additional private keys that the node has access to (the public keys can be derived from them).

The keystore repository should have 0700 permissions (readable, writable by the owner only).

The key files are named as key_base32encodedNameNoPadding where key_ is a fixed prefix followed by a base32 encoded identifier, without padding and downcased. The identifier usually corresponds to a human-friendly name given by the user.

The key files should have '0400' permissions (read-only, by the owner only).

The self key identifier is reserved for the peer's main key, and therefore key named key_onswyzq is allowed in this folder.

The key files themselves contain a serialized representation of the keys as defined in the libp2p specification.

datastore/

The datastore directory contains the data for a leveldb instance used to store operation data for the IPFS node. If the user uses a boltdb datastore instead, the directory will be named boltdb. Thus the data files of each database will not clash.

TODO: consider whether all should just be named leveldb/

logs/

IPFS implementations put event log files inside the logs/ directory. The latest log file is logs/events. Others, rotated out may exist, with a timestamp of their creation. For example:

repo.lock

repo.lock prevents concurrent access to the repo. Its content SHOULD BE the PID of the process currently holding the lock. This allows clients to detect a failed lock and cleanup.

> cat .ipfs/repo.lock
42
> ps | grep "ipfs daemon"
42 ttys000   79:05.83 ipfs daemon

TODO, ADDRESS DISCREPANCY: the go-ipfs implementation does not currently store the PID in the file, which in some systems causes failures after a failure or a teardown. This SHOULD NOT require any manual intervention-- a present lock should give new processes enough information to recover. Doing this correctly in a portable, safe way, with good UX is very tricky. We must be careful with TOCTTOU bugs, and multiple concurrent processes capable of running at any moment. The goal is for all processes to operate safely, to avoid bothering the user, and for the repo to always remain in a correct, consistent state.

version

The version file contains the repo implementation name and version. This format has changed over time:

# in version 0
> cat $repo-at-version-0/version
cat: /Users/jbenet/.ipfs/version: No such file or directory

# in versions 1 and 2
> cat $repo-at-version-1/version
1
> cat $repo-at-version-2/version
2

# in versions >3
> cat $repo-at-version-3/version
fs-repo/3

Any fs-repo implementation of any versions >0 MUST be able to read the version file. It MUST NOT change format between versions. The sole exception is version 0, which had no file.

TODO: ADDRESS DISCREPANCY: versions 1 and 2 of the go-ipfs implementation use just the integer number. It SHOULD have used fs-repo/<version-number>. We could either change the spec and always just use the int, or change go-ipfs in version >3. we will have to be backwards compatible.

Datastore

Both the /blocks and /datastore directories are controlled by the datastore component of the repo.

Notes

Location

The fs-repo can be located anywhere on the filesystem. By default clients should search for a repo in:

~/.ipfs

Users can tell IPFS programs to look elsewhere with the env var:

IPFS_PATH=/path/to/repo

blocks/ with an fs-datastore

Each object is stored in its own file. The filename is the hash of the object. The files are nested in directories whose names are prefixes of the hash, as in .git/objects.

For example:

# multihashes
1220fe389b55ea958590769f9046b0f7268bca90a92e4a9f45cbb30930f4bf89269d # sha2
1114f623e0ec7f8719fb14a18838d2a3ef4e550b5e53 # sha1

# locations of the blocks
.ipfs/blocks/1114/f6/23/e0ec7f8719fb14a18838d2a3ef4e550b5e53
.ipfs/blocks/1220/fe/38/9b55ea958590769f9046b0f7268bca90a92e4a9f45cbb30930f4bf89269d

Important Notes:

  • the hashes are encoded in hex, not the usual base58, because some filesystems are case insensitive.
  • the multihash prefix is two bytes, which would waste two directory levels, thus these are combined into one.
  • the git idx and pack file formats could be used to coalesce objects

TODO: ADDRESS DISCREPANCY:

the go-ipfs fs-repo in version 2 uses a different blocks/ dir layout:

/Users/jbenet/.ipfs/blocks
├── 12200007
│   └── 12200007d4e3a319cd8c7c9979280e150fc5dbaae1ce54e790f84ae5fd3c3c1a0475.data
├── 1220000f
│   └── 1220000fadd95a98f3a47c1ba54a26c77e15c1a175a975d88cf198cc505a06295b12.data

We MUST address whether we should change the fs-repo spec to match go-ipfs in version 2, or we should change go-ipfs to match the fs-repo spec (more tiers). We MUST also address whether the levels are a repo version parameter or a config parameter. There are filesystems in which a different fanout will have wildly different performance. These are mostly networked and legacy filesystems.

Reading without the repo.lock

Programs MUST hold the repo.lock while reading and writing most files in the repo. The only two exceptions are:

  • repo.lock - so clients may check for it
  • api - so clients may use the API