# Weeknotes: 028

## Work

• We hit another big Elasticsearch problem, namely synonyms weren’t working. The Elasticsearch documentation isn’t terribly helpful, but I’ve managed to glean that there are two types of synonyms.

Explicit mappings:

a, b, c => d, e, f

Which means “match any token sequence on the LHS and replace with all alternatives on the RHS”.

Equivalent synonyms:

a, b, c

Whose behaviour depends on the expand parameter in the schema. If expand is true (the default), it is equivalent to:

a, b, c => a, b, c

If expand is false, it is equivalent to:

a, b, c => a

We had a problem where it seemed equivalent synonyms were behaving as if expand were set to false, though that wasn’t set in our configuration, didn’t appear in the index configuration Elasticsearch reported, and explicitly setting it to true didn’t change matters. A weird situation, but explicitly expanding all the synonyms fixed the problem. Hopefully this is the last big issue.

• A smaller problem we found is that reindexing the AWS managed Elasticsearch is slow. Really slow. Our current non-managed Elasticsearch 2 cluster can reindex all of its documents (copy them from one index into another) in about 45 minutes. Our new managed Elasticsearch 5 cluster, which is using machines roughly as powerful as our Elasticsearch 2 machines, takes about two and a half hours. Figuring out why is a problem for next quarter.

• Beyond that, we were mostly working on small tasks: enabling search-related Jenkins jobs, switching on the monitoring, updating documentation, pulling the latest data from Elasticsearch 2, and preparing to switch applications over.

• March the 29th, an important day the Civil Service has long been preparing for, was this week. I am talking, of course, about pay day.

## Miscellaneous

• I changed ISP to Hyperoptic, who finished wiring my building for fibre this week. I went for the plan advertised as up to symmetric gigabit, in practice I get about 920Mbps down and 950Mbps up, which is awesome. I can actually stream things now, without it pausing every 15s to buffer. Pretty much anything I want to download only takes a couple of minutes at most. It’s also got IPv6, which I’ve never had on a home internet connection before, with my own public /64. The only small downside is that IPv4 is behind CGN, though I could get a static IPv4 address for £5/month.

• I bought a couple of new books which I’ve had my eye on for a while: Roadside Picnic, by Arkady and Boris Strugatsky; and Void Star, by Zachary Mason. They should be arriving in the next few days. I’m running dangerously low on shelf space (as usual), but even lower on space to put new shelves…