Elasticsearch REST API: JEST upsert

I’ve already written about tips and tricks when using the Elasticsearch Java API. The Elasticsearch REST API has been going from strength to strength, and it seems that going forward the Elasticsearch team will focus more on the REST API than the native JAVA client. At the time of writing however, the official java REST library doesn’t seem to have support for the abstraction of the bulk API, so I followed some advice and looked into the JEST library.

The only snag with the Jest library is that when it comes to bulk operations, the documentation only gives examples of scripted updates. The Elasticsearch update API also allows for updates using partial documents. Jest supports this functionality, but I couldn’t find good documentation for this. Here-under is an example for anyone looking for this:

The important points:

  • You can still use the official java elasticsearch client’s “XContentFactory.jsonBuilder” library to more easily build your JSON objects.
  • The trick is in line 26 above:

jsonBuilder().startObject().startObject(doc”)

This creates a nested object with “doc” as the inner JSON object, as outlined by the elasticsearch documentation:

{
    "doc" : {
        "name" : "new_name"
    }
}

The first “startObject()” creates the outer curly brackets, while the second startObject(“doc”) creates the inner “doc” object.

  • We add content to the JSON object in lines 27-29
  • Just like we had to use two startObject() calls, we need to close the object with two endObject() calls as shown in line 31

The rest of the snippet deals with the actual bulk update. We pass the object we just created into an Update Builder, which gives us a “Bulkable Object” that we can pass on to the jest bulk processor. The snippet is taken from a larger program where it resides in a loop – which explains the if/else clause in lines 37-48; it’s important to “flush” the bulk service every so often. The native java client would to this automatically – so far in Jest you need to account for this yourself

 

 

 

 

 

 

 

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Nugget Post: Insert an alert / rule name in emails sent from ElastAlert

ElastAlert is a fantastic python module that makes it easy to setup near – realtime alerts and responses to entries of interest. A quick piece of information  which I didnt find clearly documented was how to insert an alert name into a custom subject line sending email alerts. 

A typical custom email alert rule file would include something similar to the following:

alert_subject: “My Alert: {0} triggered”
alert_subject_args:
– name

The “name” variable is basically a “reserved keyword” that will be substituted with the alert name, internally the code is making a lookup in a dictionary:

if ‘alert_subject_args’ in self.rule:
alert_subject_args = self.rule[‘alert_subject_args’]

Looking at other parts of the code reveals that “self.rule” is a dictionary, which has an element called “name” containing the alert name defined in the rule file