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Considerations for full-planet builds
Pelias is designed to work with data ranging from a small city to the entire planet. Small cities do not require particularly significant resources and should be easy. However, full planet builds present many of their own challenges.
Current full planet builds weigh in at around 550 million documents, and require about 375GB total storage in Elasticsearch.
Fortunately, because of services like AWS and the scalability of Elasticsearch, full planet builds are possible without too much extra effort. The process is no different, it just requires more hardware and takes longer.
To set expectations, a cluster of 4 r4.xlarge AWS instances (30GB RAM each) running Elasticsearch, and one m4.4xlarge instance running the importers and PIP service can complete a full planet build in about two days.
Recommended processes
Use Docker containers and orchestration
We strongly recommend using Docker to run Pelias. All our services include Dockerfiles and the resulting images are pushed to Docker Hub by our CI. Using these images will drastically reduce the amount of work it takes to set up Pelias and will ensure you are on a known good configuration, minimizing the number of issues you will encounter.
Additionally, there are many great tools for managing container workloads. Simple ones like docker-compose can be used for small installations, and more complex tools like Kubernetes can be great for larger installations. Pelias is extensively tested on both.
Use separate Pelias installations for indexing and production traffic
The requirements for performant and reliable Elasticsearch clusters are very different for importing new data compared to serving queries. It is highly recommended to use one cluster to do imports, save the resulting Elasticsearch index into a snapshot, and then load that snapshot into the cluster used to perform actual geocoding.
Shard count
Historically, Mapzen Search has used 24 Elasticsearch shards for its builds. However, our latest guidance from the Elasticsearch team is that shards should be no larger than 50GB, but otherwise having as few shards as possible is best. At geocode.earth we are experimenting with 12 shard builds, and may eventually move to 6. We would appreciate performance feedback from anyone doing large builds.
The elasticsearch section of pelias.json can be used to configure the shard count.
{
"elasticsearch": {
"settings": {
"index": {
"number_of_shards": "5",
}
}
}
}
Force merge your Elasticsearch indices
Pelias Elasticserach indices are generally static, as we do not recommend querying from and importing to an Elasticsearch cluster simultaneously. In such cases, the highest levels of performance can be achieved by force-merging the Elasticsearch index.
Recommended hardware
For a production ready instance of Pelias, capable of supporting a few hundred queries per second across a full planet build, a setup like the following should be sufficient.
Elasticsearch cluster for importing
The main requirement of Elasticsearch is that it has lots of disk. 400GB across the cluster is a good minimum. Increased CPU power is useful to achieve a higher throughput for queries, but not as important as RAM.
Elasticsearch cluster for querying
For queries, essentially the only bottleneck is CPU, although more RAM is helpful so Elasticsearch
data can be cached. On AWS, c5 instances are significantly more performant than even the c4
instances, and should be used if high performance is needed.
Example configuration: 4 c5.4xlarge (16 CPU, 32GB RAM) to serve 250 RPS
Importer machine
The importers are each single-threaded Node.js processes, which require around 8GB of RAM each with admin lookup enabled. Faster CPUs will help increase the import speed. Running multiple importers in parallel is recommended if the importer machine has enough RAM and CPU to support them.
Example configuration: 1 c4.4xlarge (16 CPU, 30GB RAM), running two parallel importers
Pelias services
Each Pelias service has different memory and CPU requirements. Here are some rough guidelines:
API
RAM: 200MB per instance CPU: Single threaded, one instance can serve around 500 RPS Disk: None
Placeholder
RAM: 200MB per instance CPU: Single threaded, supports clustering Disk: Requires about 2GB for a full planet index
Libpostal
RAM: 3GB per instance CPU: Multi-threaded, but extremely fast. A single core can serve 8000+ RPS Disk: about 2-3GB of data storage required
PIP
RAM: ~6GB CPU: 2 cores per instance recommended, which is enough to serve 5000-7000 RPS
Interpolation
RAM: 3GB per instance currently (please follow our efforts to un-bundle libpostal from the interpolation service) CPU: Single core. One instance can serve around 200RPS Disk: 40GB needed for a full planet interpolation dataset