Clarifies storage versions supported vs tested (openzipkin#2623)

README.md

@@ -80,17 +80,23 @@ is for testing, for example starting a server on your laptop without any
 database needed.
 
 ### Cassandra
-The [Cassandra](zipkin-storage/cassandra) component is tested against
-Cassandra 3.11.3+. It stores spans using UDTs, such that they appear like
-the v2 Zipkin model in cqlsh. It is designed for scale. For example, it
-uses a combination of SASI and manually implemented indexes to make
-querying larger data more performant.
+The [Cassandra](zipkin-storage/cassandra) component uses Cassandra
+3.11.3+ features, but is tested against the latest patch of Cassandra 3.11.
 
-Note: This store requires a [spark job](https://github.com/apache/incubator-zipkin-dependencies) to aggregate dependency links.
+This is the second generation of our Cassandra schema. It stores spans
+using UDTs, such that they appear like Zipkin v2 json in cqlsh. It is
+designed for scale, and uses a combination of SASI and manually
+implemented indexes to make querying larger data more performant.
+
+Note: This store requires a [job to aggregate](https://github.com/apache/incubator-zipkin-dependencies) dependency links.
 
 ### Elasticsearch
-The [Elasticsearch](zipkin-storage/elasticsearch) component is tested against Elasticsearch 2-6.x.
-It stores spans as json and has been designed for larger scale.
+The [Elasticsearch](zipkin-storage/elasticsearch) component uses
+Elasticsearch 5+ features, but is tested against Elasticsearch 6-7.x.
+
+It stores spans as Zipkin v2 json so that integration with other tools is
+straightforward. To help with scale, this uses a combination of custom
+and manually implemented indexing.
 
 Note: This store requires a [spark job](https://github.com/apache/incubator-zipkin-dependencies) to aggregate dependency links.
 
@@ -120,20 +126,30 @@ data layouts based on Zipkin's V1 Thrift model, as opposed to the
 simpler v2 data model currently used.
 
 #### MySQL
-The [MySQL v1](zipkin-storage/mysql-v1) component currently is only
-tested with MySQL 5.6-7. It is designed to be easy to understand, and
-get started with. For example, it deconstructs spans into columns, so
+The [MySQL v1](zipkin-storage/mysql-v1) component uses MySQL 5.6+
+features, but is tested against MariaDB 10.3.
+
+The schema was designed to be easy to understand and get started with;
+it was not designed for performance. Ex spans fields are columns, so
 you can perform ad-hoc queries using SQL. However, this component has
 [known performance issues](https://github.com/apache/incubator-zipkin/issues/1233): queries will eventually take seconds to return
 if you put a lot of data into it.
 
+This store does not require a [job to aggregate](https://github.com/apache/incubator-zipkin-dependencies) dependency links.
+However, running the job will improve performance of dependencies
+queries.
+
 #### Cassandra
-The [Cassandra v1](zipkin-storage/cassandra-v1) component is tested
-against Cassandra 2.2+. It stores spans as opaque thrifts which means
-you can't read them in cqlsh. However, it is designed for scale. For
-example, it has manually implemented indexes to make querying larger
-data more performant. This store requires a [spark job](https://github.com/apache/incubator-zipkin-dependencies) to aggregate
-dependency links.
+The [Cassandra v1](zipkin-storage/cassandra-v1) component uses Cassandra
+2.2+ features, but is tested against the latest patch of Cassandra 3.11.
+
+The CQL was written in 2015, based on the original Cassandra schema from
+Twitter, and since been extended. Spans are stored as opaque thrifts,
+which means you cannot query fields in cqlsh. The schema was designed
+for scale, including manually implemented indexes to make querying
+larger data more performant.
+
+Note: This store requires a [job to aggregate](https://github.com/apache/incubator-zipkin-dependencies) dependency links.
 
 ## Running the server from source
 The [Zipkin server](zipkin-server) receives spans via HTTP POST and respond to queries

zipkin-storage/cassandra-v1/README.md

@@ -1,10 +1,11 @@
 # storage-cassandra
 
-This is a CQL-based Cassandra 2.2+ storage component, built upon the [Zipkin v1 thrift model](https://github.com/apache/incubator-zipkin-api/tree/master/thrift).
+This is a CQL-based Cassandra storage component, built upon the [Zipkin v1 thrift model](https://github.com/apache/incubator-zipkin-api/tree/master/thrift).
+This uses Cassandra 2.2+ features, but is tested against the latest patch of Cassandra 3.11.
 
 `CassandraSpanStore.getDependencies()` returns pre-aggregated dependency links (ex via [zipkin-dependencies](https://github.com/apache/incubator-zipkin-dependencies)).
 
-The implementation uses the [Datastax Java Driver 3.1.x](https://github.com/datastax/java-driver).
+The implementation uses the [Datastax Java Driver 3.x](https://github.com/datastax/java-driver).
 
 `zipkin2.storage.cassandra.v1.CassandraStorage.Builder` includes defaults that will
 operate against a local Cassandra installation.
@@ -19,7 +20,7 @@ See [Logging Query Latencies](https://docs.datastax.com/en/developer/java-driver/
 This module conditionally runs integration tests against a local Cassandra instance.
 
 Tests are configured to automatically access Cassandra started with its defaults.
-To ensure tests execute, download a Cassandra 2.2-3.4 distribution, extract it, and run `bin/cassandra`.
+To ensure tests execute, download a Cassandra 2.2+ distribution, extract it, and run `bin/cassandra`.
 
 If you run tests via Maven or otherwise when Cassandra is not running,
 you'll notice tests are silently skipped.

zipkin-storage/cassandra/README.md

@@ -1,10 +1,11 @@
 # storage-cassandra
 
-This is a CQL-based Cassandra 3.9+ storage component, built upon the [Zipkin v2 api and model](https://zipkin.apache.org/zipkin-api/#/default/post_spans).
+This is a CQL-based Cassandra storage component, built upon the [Zipkin v2 api and model](https://zipkin.apache.org/zipkin-api/#/default/post_spans).
+This uses Cassandra 3.11.3+ features, but is tested against the latest patch of Cassandra 3.11.
 
 `CassandraSpanStore.getDependencies()` returns pre-aggregated dependency links (ex via [zipkin-dependencies](https://github.com/apache/incubator-zipkin-dependencies)).
 
-The implementation uses the [Datastax Java Driver 3.1.x](https://github.com/datastax/java-driver).
+The implementation uses the [Datastax Java Driver 3.x](https://github.com/datastax/java-driver).
 
 `zipkin2.storage.cassandra.CassandraStorage.Builder` includes defaults that will operate against a local Cassandra installation.
 

zipkin-storage/elasticsearch/README.md

@@ -2,8 +2,8 @@
 
 This is is a plugin to the Elasticsearch storage component, which uses
 HTTP by way of [OkHttp 3](https://github.com/square/okttp) and
-[Moshi](https://github.com/square/moshi). This currently supports 5.x,
-6.x and 7.x version families.
+[Moshi](https://github.com/square/moshi). This uses Elasticsearch 5+
+features, but is tested against Elasticsearch 6-7.x.
 
 ## Multiple hosts
 Most users will supply a DNS name that's mapped to multiple A or AAAA

zipkin-storage/mysql-v1/README.md

@@ -1,9 +1,9 @@
 # storage-mysql-v1
-
 This MySQL (Legacy) storage component includes a blocking `SpanStore` and span consumer function.
 `SpanStore.getDependencies()` aggregates dependency links on-demand.
 
-The implementation uses JOOQ to generate MySQL SQL commands. It is only tested on MySQL 5.6-5.7.
+The implementation uses JOOQ to generate MySQL SQL commands. MySQL 5.6+
+features are used, but tests run against MariaDB 10.3.
 
 See the [schema DDL](src/main/resources/mysql.sql).