github.com/kivutar/go-ethereum@v1.7.4-0.20180117074026-6fdb126e9630/node/doc.go (about)

     1  // Copyright 2016 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  /*
    18  Package node sets up multi-protocol Ethereum nodes.
    19  
    20  In the model exposed by this package, a node is a collection of services which use shared
    21  resources to provide RPC APIs. Services can also offer devp2p protocols, which are wired
    22  up to the devp2p network when the node instance is started.
    23  
    24  
    25  Resources Managed By Node
    26  
    27  All file-system resources used by a node instance are located in a directory called the
    28  data directory. The location of each resource can be overridden through additional node
    29  configuration. The data directory is optional. If it is not set and the location of a
    30  resource is otherwise unspecified, package node will create the resource in memory.
    31  
    32  To access to the devp2p network, Node configures and starts p2p.Server. Each host on the
    33  devp2p network has a unique identifier, the node key. The Node instance persists this key
    34  across restarts. Node also loads static and trusted node lists and ensures that knowledge
    35  about other hosts is persisted.
    36  
    37  JSON-RPC servers which run HTTP, WebSocket or IPC can be started on a Node. RPC modules
    38  offered by registered services will be offered on those endpoints. Users can restrict any
    39  endpoint to a subset of RPC modules. Node itself offers the "debug", "admin" and "web3"
    40  modules.
    41  
    42  Service implementations can open LevelDB databases through the service context. Package
    43  node chooses the file system location of each database. If the node is configured to run
    44  without a data directory, databases are opened in memory instead.
    45  
    46  Node also creates the shared store of encrypted Ethereum account keys. Services can access
    47  the account manager through the service context.
    48  
    49  
    50  Sharing Data Directory Among Instances
    51  
    52  Multiple node instances can share a single data directory if they have distinct instance
    53  names (set through the Name config option). Sharing behaviour depends on the type of
    54  resource.
    55  
    56  devp2p-related resources (node key, static/trusted node lists, known hosts database) are
    57  stored in a directory with the same name as the instance. Thus, multiple node instances
    58  using the same data directory will store this information in different subdirectories of
    59  the data directory.
    60  
    61  LevelDB databases are also stored within the instance subdirectory. If multiple node
    62  instances use the same data directory, openening the databases with identical names will
    63  create one database for each instance.
    64  
    65  The account key store is shared among all node instances using the same data directory
    66  unless its location is changed through the KeyStoreDir configuration option.
    67  
    68  
    69  Data Directory Sharing Example
    70  
    71  In this example, two node instances named A and B are started with the same data
    72  directory. Mode instance A opens the database "db", node instance B opens the databases
    73  "db" and "db-2". The following files will be created in the data directory:
    74  
    75     data-directory/
    76          A/
    77              nodekey            -- devp2p node key of instance A
    78              nodes/             -- devp2p discovery knowledge database of instance A
    79              db/                -- LevelDB content for "db"
    80          A.ipc                  -- JSON-RPC UNIX domain socket endpoint of instance A
    81          B/
    82              nodekey            -- devp2p node key of node B
    83              nodes/             -- devp2p discovery knowledge database of instance B
    84              static-nodes.json  -- devp2p static node list of instance B
    85              db/                -- LevelDB content for "db"
    86              db-2/              -- LevelDB content for "db-2"
    87          B.ipc                  -- JSON-RPC UNIX domain socket endpoint of instance A
    88          keystore/              -- account key store, used by both instances
    89  */
    90  package node