While any Node in the Network can accept Transaction requests, the Transactions are usually submitted to the Proxy application, which maintains a list of Nodes - Observers - to forward Transaction requests to - these Observers are selected in such manner that any Transaction submitted to them will be processed by the Network as soon and as efficiently as possible.
The Proxy will submit a Transaction on behalf of the user to the REST API of one of its listed Observers, selected for (a) being online at the moment and (b) being located within the Shard to which the Sender's Account belongs. After receiving the Transaction on its REST API, that specific Observer will propagate the Transaction throughout the Network, which will lead to its execution.
The Observer Nodes of the Proxy thus act as a default dedicated entry point into the Network.
It is worth repeating here, though, that submitting a Transaction through the Proxy is completely optional - any Node of the Network will accept Transactions to propagate, given it has not disabled its REST API.
In the figure above:
The Elrond Network - consisting of Nodes grouped within Shards. Some of these Nodes are Observers.
One or more instances of the Elrond Proxy - including the official one - connect to Observer Nodes in order to forward incoming user Transactions to the Network and to query state within the Blockchain.
The client applications connect to the Network through the Elrond Proxy. Is is also possible for a blockchain-powered application to talk directly to an Observer or even to a Validator.
The official instance of the Elrond Proxy is located at https://api.elrond.com.
In order to host a Proxy instance on a web server, one has to first clone and build the repository:
git clone https://github.com/ElrondNetwork/elrond-proxy-go.gitcd elrond-proxy-go/cmd/proxygo build .
The Proxy holds its configuration within the
config.toml - this is the main configuration file. It has to be adjusted so that the Proxy points to a list of chosen Observer Nodes.
economics.toml - this file should not be normally altered. It must be kept in sync with the economics configuration of the Network.
external.toml - this file holds configuration necessary to Proxy components that interact with external systems. An example of such an external system is Elastic Search - currently, Elrond Proxy requires an Elastic Search instance to implement some of its functionality.
Currently, two routes provided by the REST API - namely Get Address Transactions and Get Block - resolve the requested resources by querying an Elastic Search instance. This is subject to change. Therefore, if one desires to host a separate Elrond Proxy instance instead of using the official (default) instance, we recommend disabling the Elastic Search Connector by adjusting the configuration file
external.toml - the previously mentioned routes will not work, but the rest of Proxy's functionality is unaffected.