<p>I am having issues trying to get logs into elasticsearch from fluentd in a k8s cluster.</p>

<p>I have several web applications which output their logs as json. Using a simple setup locally with docker containers I can get elastic to read and parse the logs correctly. Here is a sample of the local json shown in kibana:</p>

<pre><code>{
  "_index": "logstash-2020.01.17",
  "_type": "fluentd",
  "_id": "S620sm8B2LEvFR841ylg",
  "_version": 1,
  "_score": null,
  "_source": {
    "log": {
      "@timestamp": "2020-01-17T08:53:03.066290",
      "caller": "StaticFileHelper.py::get",
      "data": {
        "python.thread": "Thread-1[{record.thread}]",
        "python.lineno": 45,
        "python.filename": "StaticFileHelper.py",
        "python.logger_name": "root",
        "python.module": "StaticFileHelper",
        "python.funcName": "get",
        "python.pid": 11239
      },
      "message": "application/javascript",
      "level": "INFO"
    },
    "@timestamp": "2020-01-17T08:53:03.000000000+00:00"
  },
  "fields": {
    "@timestamp": [
      "2020-01-17T08:53:03.000Z"
    ],
    "log.@timestamp": [
      "2020-01-17T08:53:03.066Z"
    ]
  },
  "sort": [
    1579251183000
  ]
}
</code></pre>

<p>Under the index patterns I can see the correct mappings. The mappings update when I introduce new fields into the logging output. Sample of output here:</p>

<pre><code>log.@timestamp: date
log.caller: string
log.caller.keyword: string
log.data.python.filename: string
log.data.python.filename.keyword: string
log.data.python.funcName :string
</code></pre>

<p>In the cluster the "log" field is not being parsed correctly:</p>

<pre><code>{
  "_index": "logstash-2020.01.17",
  "_type": "fluentd",
  "_id": "atUDs28BFgXM_nqQvYUY",
  "_version": 1,
  "_score": null,
  "_source": {
    "log": "{'@timestamp': '2020-01-17T10:19:21.775339', 'caller': 'RequestLoggingManager.py::print_request_id', 'data': {'python.thread': 'MainThread[{record.thread}]', 'python.lineno': 28, 'python.filename': 'RequestLoggingManager.py', 'python.logger_name': 'root', 'python.module': 'RequestLoggingManager', 'python.funcName': 'print_request_id', 'request_id': '1579256361-1494-XYyVj', 'python.pid': 8}, 'message': 'request: \"1579256361-1497-JUeYF\" is about to enter \"get_settings\"', 'level': 'INFO'}\n",
    "stream": "stderr",
    "docker": {
      "container_id": "fc5b0d5b0aa4008961b18dfe93c4e04b2cfbde0f7ff072dc702c55823baba3a4"
    },
    "kubernetes": {
      "container_name": "cms",
      "namespace_name": "default",
      "pod_name": "cms-68c4b49657-b88hs",
      "container_image": "HIDDEN",
      "container_image_id": "HIDDEN",
      "pod_id": "ffc6a681-390b-11ea-bcac-42010a8000be",
      "labels": {
        "app": "cms",
        "pod-template-hash": "68c4b49657",
        "version": "1.0.0"
      },
      "host": "HIDDEN",
      "master_url": "https://10.0.0.1:443/api",
      "namespace_id": "1ede7315-14fa-11ea-95c1-42010a80010f"
    },
    "@timestamp": "2020-01-17T10:19:21.776876369+00:00",
    "tag": "kubernetes.var.log.containers.cms-68c4b49657-b88hs_default_cms-fc5b0d5b0aa4008961b18dfe93c4e04b2cfbde0f7ff072dc702c55823baba3a4.log"
  },
  "fields": {
    "@timestamp": [
      "2020-01-17T10:19:21.776Z"
    ]
  },
  "highlight": {
    "kubernetes.labels.app": [
      "@kibana-highlighted-field@cms@/kibana-highlighted-field@"
    ]
  },
  "sort": [
    1579256361776
  ]
}
</code></pre>

<p>The mapping are being shown as:</p>

<pre><code>log: string
log.keyword: string
</code></pre>

<p>None of the custom json mappings are recognised.</p>

<p>Is there a way of customising this "log" field and if so where do I need to make the changes? I am quite new to fluentd and elastic so any help would be appreciated!</p>

<p>I am using the fluent/fluentd-kubernetes-daemonset on kubernetes.</p>

<p>To get around this I pulled and ran the fluent/fluentd-kubernetes-daemonset:v1.4.2-debian-elasticsearch-1.1 image locally in docker. Had to make sure I specified FLUENT_ELASTICSEARCH_USER and FLUENT_ELASTICSEARCH_PASSWORD as env variables on the initial run as the entrypoint.sh tries to substitute information in the containers fluent.conf file. If you don't specify a password it wipes out the information in the file.</p>

<p>Then it was a case of exec'ing into the running container and adding the following information into fluent.conf:</p>

<pre><code>filter **&gt;
  @type record_transformer
  &lt;record&gt;
    log_json ${record["log"]}
  &lt;/record&gt;
&lt;/filter&gt;


&lt;filter **&gt;
  @type parser
  @log_level debug
  key_name log_json
  reserve_data true
  remove_key_name_field true
  emit_invalid_record_to_error false
  &lt;parse&gt;
    @type json
  &lt;/parse&gt;
&lt;/filter&gt;
</code></pre>

<p>After this I exited and stopped the container, committed the container to a brand new image in my own repo on Docker Hub and referenced the new image in the DaeomnSet yaml file which we were using to deploy up to k8s.</p>

<p>This may not be the slickest or the most efficient method but in the absence of any docs on how to customise the fluentd.conf, this did the trick for now.</p>
