Elasticsearch guides

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  • Bootstrap Checks
    Bootstrap Checks in Elasticsearch Overview Elasticsearch has many settings that can cause significant performance problems if not set correctly. To prevent this happening Elasticsearch will carry out what are known as bootstrap checks to ensure that these important settings have been covered.   If any of the checks fail then elasticsearch will write an error to the logs and will not start. Bootstrap checks are carried out when the network.host setting in network.host:(...) - Read More
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  • Disk Watermark
    Disk watermarks in Elasticsearch Elasticsearch considers the available disk space before deciding whether to allocate new shards, relocate shards away or put all indices on read mode based on a different threshold of this error. The reason is Elasticsearch indices consists of different shards which are persisted on data nodes and low disk space can cause issues. Relevant settings related  cluster.routing.allocation.disk.watermark and have(...) - Read More
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  • Elasticsearch auto complete Guide
    How to avoid critical performance mistakes, implementation considerations and why the Elasticsearch default solution doesn't cut it Background All modern-day websites have autocomplete features on their search bar to improve user experience (no one wants to type entire search terms...). It's imperative that the autocomplete be faster than the standard search, as the whole point of autocomplete is to start showing the results while the user is typing. If the latency is high,(...) - Read More
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  • Low Disk Watermark Threshold
    What Does it Mean? There are various “watermark” thresholds on your Elasticsearch cluster.  As the disk fills up on a node, the first threshold to be crossed will be the “low disk watermark”.  Once this threshold is crossed, the Elasticsearch cluster will stop allocating replica shards to that node.  This means that your cluster may become YELLOW. How to Resolve it Passing this threshold is a warning and you should not delay in taking action before the higher thresholds are(...) - Read More
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  • Red Status
    A red status indicates that one or more indices do not have allocated primary shards.  The causes may be similar to those described in Status Yellow, but certainly indicate that  something is not right with the cluster. What does it mean? A red status indicates that not only has the primary shard been lost, but also that a replica has not been promoted to primary in its place.  However, just as with yellow status, you should not panic and start firing off commands without(...) - Read More
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  • Search Latency In-Depth Guide
    Opster incorporates deep knowledge learned from some of the best Elasticsearch experts around the world. This troubleshooting guide is based on our very own Elasticsearch expert’s first-hand encounter with a burst of search traffic and focuses on how the correct configuration of primary shards and replicas can help ES  handle such cases (explained through a case study). For the basic internals and optimization of shards and replicas please visit our blog post: Elasticsearch Shards and(...) - Read More
  • Slow Log Search Queries
    Overview Search Queries Slow Log can be very handy while troubleshooting Elasticsearch performance issues. There are two main operations in Elasticsearch (search and indexing) and both are logged separately.  This troubleshooting snippet targets the Search heavy systems where search TPS (Transaction per second) is much higher than the indexing TPS, such as with e-commerce sites or medium, Quora-like platforms. Slow queries are often caused by:  Poorly written or expensive search(...) - Read More
  • Split Brain
    Overview Elasticsearch is a distributed system and may contain one more node in each cluster. For a cluster to become operational, Elasticsearch needs a quorum of a minimum number of master nodes. By default, every node in Elasticsearch is master eligible. These master nodes are responsible for all the cluster coordination tasks to manage the cluster state.  When you create a cluster, no matter how many nodes you are configuring, the quorum is by default set to one. That means if a(...) - Read More
  • Status Yellow
    There are several reasons why your Elasticsearch cluster could indicate a yellow status. What does it mean? Yellow status indicates that one or more of the replica shards on the Elasticsearch cluster are not allocated to a node. No need to  panic! There are several reasons why a yellow status can be perfectly normal, and in many cases Elasticsearch will recover to green by itself, so the worst thing you can do is start tweaking things without knowing exactly what the cause is.(...) - Read More