besu/docs/Using-Pantheon/Accessing-Logs-Using-JSON-RPC.md

Accessing Logs Using JSON-RPC API Methods

Access logs using JSON-RPC API methods:

• eth_getFilterChanges
• eth_getFilterLogs
• eth_getLogs

Use eth_newFilter to create the filter before using eth_getFilterChanges and eth_getFilterLogs).

!!! note The following examples are created using the sample contract included in Events and Logs.

Creating a Filter

Create a filter using eth_newFilter.

!!! example

If the [example contract](Events-and-Logs.md#example) was deployed to 0x42699a7612a82f1d9c36148af9c77354759b210b, the 
following request for `eth_newFilter` creates a filter to log when `valueIndexed` is set to 5: 

```json
{
 "jsonrpc":"2.0",
 "method":"eth_newFilter",
 "params":[
    {
      "fromBlock":"earliest", 
      "toBlock":"latest", 
      "address":"0x42699a7612a82f1d9c36148af9c77354759b210b", 
      "topics":[
          ["0xd3610b1c54575b7f4f0dc03d210b8ac55624ae007679b7a928a4f25a709331a8"], 
          ["0x0000000000000000000000000000000000000000000000000000000000000005"]
      ]
     }
  ],
  "id":1
}
```

eth_newFilter returns a filter ID hash (for example, 0x1ddf0c00989044e9b41cc0ae40272df3).

Polling Filter for Changes

To poll the filter for changes that have occurred since the last poll, use eth_getFilterChanges with the filter ID hash returned by eth_newFilter.

!!! example

If the contract had been executed twice since the last poll, with `valueIndexed` set to 1 and 5, 
[`eth_getFilterChanges`](../Reference/JSON-RPC-API-Methods.md#eth_getfilterchanges) returns
only the log where the [topic](Events-and-Logs.md#event-parameters) for `valueIndexed` is 5: 

```json
{
    "jsonrpc": "2.0",
    "id": 1,
    "result": [
        {
            "logIndex": "0x0",
            "removed": false,
            "blockNumber": "0x21c",
            "blockHash": "0xc7e6c9d5b9f522b2c9d2991546be0a8737e587beb6628c056f3c327a44b45132",
            "transactionHash": "0xfd1a40f9fbf89c97b4545ec9db774c85e51dd8a3545f969418a22f9cb79417c5",
            "transactionIndex": "0x0",
            "address": "0x42699a7612a82f1d9c36148af9c77354759b210b",
            "data": "0x0000000000000000000000000000000000000000000000000000000000000005",
            "topics": [
                "0xd3610b1c54575b7f4f0dc03d210b8ac55624ae007679b7a928a4f25a709331a8",
                "0x0000000000000000000000000000000000000000000000000000000000000005"
            ]
        }
    ]
}
```

Getting All Logs for a Filter

To get all logs for a filter, use eth_getFilterLogs.

!!! example

If the contract had been executed twice with `valueIndexed` set to 5 since the filter was created using `eth_newFilter`,
`eth_getFilterLogs` returns: 

```json
{
    "jsonrpc": "2.0",
    "id": 1,
    "result": [
        {
            "logIndex": "0x0",
            "removed": false,
            "blockNumber": "0x1a7",
            "blockHash": "0x4edda22a242ddc7bc51e2b6b11e63cd67be1af7389470cdea9c869768ff75d42",
            "transactionHash": "0x9535bf8830a72ca7d0020df0b547adc4d0ecc4321b7d5b5d6beb1eccee5c0afa",
            "transactionIndex": "0x0",
            "address": "0x42699a7612a82f1d9c36148af9c77354759b210b",
            "data": "0x0000000000000000000000000000000000000000000000000000000000000005",
            "topics": [
                "0xd3610b1c54575b7f4f0dc03d210b8ac55624ae007679b7a928a4f25a709331a8",
                "0x0000000000000000000000000000000000000000000000000000000000000005"
            ]
        },
        {
            "logIndex": "0x0",
            "removed": false,
            "blockNumber": "0x21c",
            "blockHash": "0xc7e6c9d5b9f522b2c9d2991546be0a8737e587beb6628c056f3c327a44b45132",
            "transactionHash": "0xfd1a40f9fbf89c97b4545ec9db774c85e51dd8a3545f969418a22f9cb79417c5",
            "transactionIndex": "0x0",
            "address": "0x42699a7612a82f1d9c36148af9c77354759b210b",
            "data": "0x0000000000000000000000000000000000000000000000000000000000000005",
            "topics": [
                "0xd3610b1c54575b7f4f0dc03d210b8ac55624ae007679b7a928a4f25a709331a8",
                "0x0000000000000000000000000000000000000000000000000000000000000005"
            ]
        }
    ]
}
```

!!! tip You can use eth_getLogs with a filter options object to get all logs matching the filter options instead of using eth_newFilter followed by eth_getFilterLogs.

Uninstalling a Filter

When you are finished using a filter, use eth_uninstallFilter to remove the filter.

Getting Logs Using a Filter Options Object

To get all logs for a filter options object, use eth_getLogs.

!!! example

The following request for `eth_getLogs` returns all the logs where the example contract has been 
deployed to 0x42699a7612a82f1d9c36148af9c77354759b210b and executed with `valueIndexed` set to 5.

```json
{
  "jsonrpc":"2.0",
  "method":"eth_getLogs",
  "params":[
    {
      "fromBlock":"earliest", 
      "toBlock":"latest", 
      "address":"0x42699a7612a82f1d9c36148af9c77354759b210b", 
      "topics":[
        ["0xd3610b1c54575b7f4f0dc03d210b8ac55624ae007679b7a928a4f25a709331a8"], 
        ["0x0000000000000000000000000000000000000000000000000000000000000005"]
      ]
	  }
  ], 
  "id":1
}
``` 

This returns the same result as calling [eth_newFilter](#creating-a-fitler) followed by [eth_getFilterLogs](#getting-all-logs-for-a-filter).