[docs] indexing transactions and subscribing to events

Refs #1643

docs/index.rst

@@ -55,6 +55,8 @@ Tendermint 102
    abci-spec.rst
    app-architecture.rst
    app-development.rst
+   subscribing-to-events-via-websocket.rst
+   indexing-transactions.rst
    how-to-read-logs.rst
 
 Tendermint 201

docs/indexing-transactions.rst

@@ -0,0 +1,100 @@
+Indexing Transactions
+=====================
+
+Tendermint allows you to index transactions and later query or subscribe to
+their results.
+
+Let's take a look at the ``[tx_index]`` config section:
+
+::
+
+    ##### transactions indexer configuration options #####
+    [tx_index]
+
+    # What indexer to use for transactions
+    #
+    # Options:
+    #   1) "null" (default)
+    #   2) "kv" - the simplest possible indexer, backed by key-value storage (defaults to levelDB; see DBBackend).
+    indexer = "kv"
+
+    # Comma-separated list of tags to index (by default the only tag is tx hash)
+    #
+    # It's recommended to index only a subset of tags due to possible memory
+    # bloat. This is, of course, depends on the indexer's DB and the volume of
+    # transactions.
+    index_tags = ""
+
+    # When set to true, tells indexer to index all tags. Note this may be not
+    # desirable (see the comment above). IndexTags has a precedence over
+    # IndexAllTags (i.e. when given both, IndexTags will be indexed).
+    index_all_tags = false
+
+By default, Tendermint will index all transactions by their respective hashes
+using an embedded simple indexer. Note, we are planning to add more options in
+the future (e.g., Postgresql indexer).
+
+Adding tags
+-----------
+
+In your application's ``DeliverTx`` method, add the ``Tags`` field with the
+pairs of UTF-8 encoded strings (e.g. "account.owner": "Bob", "balance":
+"100.0", "date": "2018-01-02").
+
+Example:
+
+::
+
+    func (app *KVStoreApplication) DeliverTx(tx []byte) types.Result {
+        ...
+        tags := []cmn.KVPair{
+          {[]byte("account.name"), []byte("igor")},
+          {[]byte("account.address"), []byte("0xdeadbeef")},
+          {[]byte("tx.amount"), []byte("7")},
+        }
+        return types.ResponseDeliverTx{Code: code.CodeTypeOK, Tags: tags}
+    }
+
+If you want Tendermint to only index transactions by "account.name" tag, in the
+config set ``tx_index.index_tags="account.name"``. If you to index all tags,
+set ``index_all_tags=true``
+
+Note, there are a few predefined tags:
+
+- ``tm.event`` (event type)
+- ``tx.hash`` (transaction's hash)
+- ``tx.height`` (height of the block transaction was committed in)
+
+Tendermint will throw a warning if you try to use any of the above keys.
+
+Quering transactions
+--------------------
+
+You can query the transaction results by calling ``/tx_search`` RPC endpoint:
+
+::
+
+    curl "localhost:46657/tx_search?query=\"account.name='igor'\"&prove=true"
+
+Check out `API docs <https://tendermint.github.io/slate/?shell#txsearch>`__ for more
+information on query syntax and other options.
+
+Subscribing to transactions
+---------------------------
+
+Clients can subscribe to transactions with the given tags via Websocket by
+providing a query to ``/subscribe`` RPC endpoint.
+
+::
+
+    {
+        "jsonrpc": "2.0",
+        "method": "subscribe",
+        "id": "0",
+        "params": {
+            "query": "account.name='igor'"
+        }
+    }
+
+Check out `API docs <https://tendermint.github.io/slate/#subscribe>`__ for more
+information on query syntax and other options.

docs/subscribing-to-events-via-websocket.rst

@@ -0,0 +1,28 @@
+Subscribing to events via Websocket
+===================================
+
+Tendermint emits different events, to which you can subscribe via `Websocket
+<https://en.wikipedia.org/wiki/WebSocket>`__. This can be useful for
+third-party applications (for analysys) or inspecting state.
+
+`List of events <https://godoc.org/github.com/tendermint/tendermint/types#pkg-constants>`__
+
+You can subscribe to any of the events above by calling ``subscribe`` RPC method via Websocket.
+
+::
+
+    {
+        "jsonrpc": "2.0",
+        "method": "subscribe",
+        "id": "0",
+        "params": {
+            "query": "tm.event='NewBlock'"
+        }
+    }
+
+Check out `API docs <https://tendermint.github.io/slate/#subscribe>`__ for more
+information on query syntax and other options.
+
+You can also use tags, given you had included them into DeliverTx response, to
+query transaction results. See `Indexing transactions
+<./indexing-transactions.html>`__ for details.