Add versioning to perf SQL database

perf/DESIGN.md

 DESIGN
 ======
 
 
 Overview
 --------
 Provides interactive dashboard for Skia performance data.
 
 Code Locations
 --------------
@@ skipping 178 matching lines @@
 
     $ mysql -h 173.194.104.24 -u root -p
 
 
     mysql> use skia
 
     mysql> show tables;
 
 Initial setup of the database, the users, and the tables:
 
+* Create the database and set up permissions. Execute the following after
+  you connect to a MySQL database (not necessary for SQLite).
+
     CREATE DATABASE skia;
     USE skia;
     CREATE USER 'readonly'@'%' IDENTIFIED BY <password in valentine>;
     GRANT SELECT ON *.* TO 'readonly'@'%';
     CREATE USER 'readwrite'@'%' IDENTIFIED BY <password in valentine>;
     GRANT SELECT, DELETE, UPDATE, INSERT ON *.* TO 'readwrite'@'%';
 
-    CREATE TABLE shortcuts (
-      id      INT             NOT NULL AUTO_INCREMENT PRIMARY KEY,
-      traces  MEDIUMTEXT      NOT NULL
-    );
+* Create the versioned database tables.
 
-    CREATE TABLE clusters (
-      id         INT          NOT NULL AUTO_INCREMENT PRIMARY KEY,
-      ts         BIGINT       NOT NULL,
-      hash       TEXT         NOT NULL,
-      regression FLOAT        NOT NULL,
-      cluster    MEDIUMTEXT   NOT NULL,
-      status     TEXT         NOT NULL,
-      message    TEXT         NOT NULL
-    );
+  We use the 'migrateDB' tool to keep the database in a well defined (versioned)
+  state. The 'db_conn_string' flag allows to specify the target database.
+  By default it will try to connect to the production environment.
+  But for testing a local MySQL database can be provided. If it cannot
+  connect to MySQL it will fall back to SQLite.
 
-    CREATE TABLE tries (
-      issue       VARCHAR(255) NOT NULL PRIMARY KEY,
-      lastUpdated BIGINT       NOT NULL,
-      results     LONGTEXT   NOT NULL
-    );
+  Bring the production database to the latest schema version:
+
+     $ migrateDB -logtostderr=true
+
+  Bring a local database to the latest schema version:
+
+     $ migrateDB -logtostderr=true -db_conn_string="root:%s@tcp(localhost:3306)/skia?parseTime=true"
+
+  Bring a local SQLite database to the latest schema version:
+
+     $ migrateDB -logtostderr=true -db_conn_string=""
+
 
 Clustering
 ----------
 
 The clustering is done by using k-means clustering over normalized Traces. The
 Traces are normalized by filling in missing data points so that there is a
 data point for every commit, and then scaling the data to have a mean of 0.0
 and a standard deviation of 1.0. See the docs for ctrace.NewFullTrace().
 
 The distance metric used is Euclidean distance between the traces.
@@ skipping 169 matching lines @@
 config, os, etc.) and select exactly two configs from it to compare against in
 the query (say, "8888" and "gpu"). We then organize the data to calculate the
 ratio of the benches from the two choices in the criteria (vertical) where all
 other parameters are the same. For instance, we calculate the ratio of benches
 in the "config" vertical from the following two traces:
 
     x86_64:HD7770:ShuttleA:Win8:gradient_create_opaque_640_480:gpu
     x86_64:HD7770:ShuttleA:Win8:gradient_create_opaque_640_480:8888
 
 and put the value into the cell in a table that has
-_row_gradient_create_opaque_640_480_ and 
+_row_gradient_create_opaque_640_480_ and
 column _x86_64:HD7770:ShuttleA:Win8_. Basically, the table row will be the
 "test" name, and the column will be the rest of the keys. The number of columns
 will be the number of perf bots we run (20+ for now).
 
 The value will then tell us if the performance is better (<1) or worse (>1) for
 gpu against 8888. We can then heatmap-color the table cells by their value
 ranges, to provide a visual way for users to identify the problems in cell
 groups. By sorting the rows with aggregated performance, users will be able to
 pinpoint the benches with worst/best relative performance to look into.
 
@@ skipping 24 matching lines @@
 
 But sysv init only handles starting and stopping a program once, so we use
 Monit to monitor the application and restart it if it crashes. The config
 is in:
 
     /etc/monit/conf.d/perf
 
 Installation
 ------------
 See the README file.