When BulkProcessor retries failed item requests then the same `IndexRequest` instance are used in a new `BulkRequest` for a retry. This is a problem when `BulkProcessor` is used from within Elasticsearch (this is the case for deprecation index logging, ilm/slm history and more), because the bulk request transport action may have set the `autoGeneratedTimestamp` field. 

If that is the case then error such a these may appear in the logs and the `BulkProcessor` retry fails:

```
Bulk write of 1 deprecation logs failed: autoGeneratedTimestamp should not be set externally
java.lang.IllegalArgumentException: autoGeneratedTimestamp should not be set externally
	at org.elasticsearch.action.bulk.TransportBulkAction.doInternalExecute(TransportBulkAction.java:223) ~[elasticsearch-7.16.1.jar:7.16.1]
	at org.elasticsearch.action.bulk.TransportBulkAction$1.doRun(TransportBulkAction.java:192) ~[elasticsearch-7.16.1.jar:7.16.1]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) [elasticsearch-7.16.1.jar:7.16.1]
	at org.elasticsearch.action.bulk.TransportBulkAction.doExecute(TransportBulkAction.java:200) [elasticsearch-7.16.1.jar:7.16.1]
	at org.elasticsearch.action.bulk.TransportBulkAction.doExecute(TransportBulkAction.java:91) [elasticsearch-7.16.1.jar:7.16.1]
```

In the bulk transport action, for each bulk item request of the `BulkRequest` its `process()` method is invoked. Incase of `IndexRequest` when no _id has been specified an id is generated and in that case the `IndexRequest#autoGeneratedTimestamp ` field is set. If the bulk request fails at a later stage, for example because there was no capacity on the node that hosts a primary shard to index documents then the bulk response will contain a `EsRejectedExecutionException` exception in the `BulkResponse` for the bulk items this failure occurred for. This is normal behaviour. However the `BulkProcessor` has retry logic and `EsRejectedExecutionException` is deemed retry-able. The `BulkProcessor` [reuses the same bulk request item instances ](https://github.com/elastic/elasticsearch/blob/master/server/src/main/java/org/elasticsearch/action/bulk/Retry.java#L139)(`IndexRequest` in this case) upon retry. This causes the failure mentioned in the stack trace.
server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
if (out.getVersion().onOrAfter(Version.V_7_13_0)) {
            out.writeMap(dynamicTemplates, StreamOutput::writeString, StreamOutput::writeString);
        } else {
            if (dynamicTemplates.isEmpty() == false) {
                throw new IllegalArgumentException("[dynamic_templates] parameter requires all nodes on " + Version.V_7_13_0 + " or later");
            }
        }
    }
    @Override
    public String toString() {
        String sSource = "_na_";
        try {
            if (source.length() > MAX_SOURCE_LENGTH_IN_TOSTRING) {
                sSource = "n/a, actual length: ["
                    + new ByteSizeValue(source.length()).toString()
                    + "], max length: "
                    + new ByteSizeValue(MAX_SOURCE_LENGTH_IN_TOSTRING).toString();
            } else {
                sSource = XContentHelper.convertToJson(source, false);
            }
        } catch (Exception e) {
            
        }
        return "index {[" + index + "][" + id + "], source[" + sSource + "]}";
    }
    @Override
    public boolean includeDataStreams() {
        return true;
    }
    /**