Before you read this guide, we recommend you run the Elasticsearch Error Check-Up which detects issues in ES causing log errors (free tool that requires no installation).
This guide will help you check for common problems that cause the log “could not read search request. unexpected boolean field” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: request, search, plugin.
Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to discover the cause of many errors and provides suitable actionable recommendations how to resolve them (join over 700 users who use this free tool).
Search in Elasticsearch
What it is:
Search refers to the searching of documents in an index or multiple indices. The simple search is just a GET request to the _search endpoint. The search query can either be provided in query string or through a request body.
Examples:
When looking for any documents in this index, if search parameters are not provided, every document is a hit and by default 10 hits will be returned.
GET my_documents/_search
A JSON object is returned in response to a search query. A 200 response code will mean the request completed successfully.
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 2,
"successful" : 2,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 1.0,
"hits" : [
...
]
}
}Notes:
- Distributed search is challenging and every shard of the index needs to be searched for hits, and then those hits are combined into a single sorted list as a final result.
- There are two phases of search: the query phase and the fetch phase.
- In the query phase, the query is executed on each shard locally and top hits are returned to the coordinating node. The coordinating node merges the results and creates a global sorted list.
- In the fetch phase, the coordinating node brings the actual documents for those hit IDs and returns them to the requesting client.
- A coordinating node needs enough memory and CPU in order to handle the fetch phase.
Plugin in Elasticsearch
What it is:
A plugin is used to enhance the core functionalities of Elasticsearch. Elasticsearch provides some core plugins as a part of their release installation. In addition to those core plugins, it is possible to write your own custom plugins as well. There are several community plugins available on GitHub for various use cases.
Examples:
- Get all the instructions for the plugin
sudo bin/elasticsearch-plugin -h
- Installing the S3 plugin for storing Elasticsearch snapshots on S3
sudo bin/elasticsearch-plugin install repository-s3
- Removing a plugin
sudo bin/elasticsearch-plugin remove repository-s3
- Installing a plugin using the file’s path
sudo bin/elasticsearch-plugin install file:///path/to/plugin.zip
Notes:
- Plugins are installed and removed using the elasticsearch-plugin script, which ships as a part of the Elasticsearch installation and can be found inside the bin/ directory of the Elasticsearch installation path.
- A plugin has to be installed on every node of the cluster and each of the nodes has to be restarted to make the plugin visible.
- You can also download the plugin manually and then install it using the elasticsearch-plugin install command, providing the file name/path of the plugin’s source file.
- When a plugin is removed, you will need to restart every elasticsearch node in order to complete the removal process.
Common Problems:
- Managing permission issues during and after plugin installation is the most common problem. If Elasticsearch was installed using the deb or rpm package then the plugin has to be installed using the root user, or else you can install the plugin as the user that owns all of the Elasticsearch files.
- In case of deb or rpm package installation, it is important to check the permission of the plugins directory after plugin installation and update the permission if it has been modified using the following command:
chown -R elasticsearch:elasticsearch path_to_plugin_directory
- If your Elasticsearch nodes are running in a private subnet without internet access, you cannot install a plugin directly. In this case, you can simply download the plugins at once and copy the files inside the plugins directory of the Elasticsearch installation path on every node. The node has to be restarted in this case as well.
Log Context
Log”could not read search request. unexpected boolean field [“classname is WatcherSearchTemplateRequest.java We extracted the following from Elasticsearch source code for those seeking an in-depth context :
}
} else if (token == XContentParser.Token.VALUE_BOOLEAN) {
if (REST_TOTAL_HITS_AS_INT_FIELD.match(currentFieldName; parser.getDeprecationHandler())) {
totalHitsAsInt = parser.booleanValue();
} else {
throw new ElasticsearchParseException("could not read search request. unexpected boolean field [" +
currentFieldName + "]");
}
} else {
throw new ElasticsearchParseException("could not read search request. unexpected token [" + token + "]");
}
