Allow disabling the physical storage cache with 'disable_cache'.

Fixes #674.

CHANGELOG.md

@@ -7,6 +7,7 @@ DEPRECATIONS/BREAKING CHANGES:
 IMPROVEMENTS:
 
  * api: API client now uses a 30 second timeout instead of indefinite [GH-681]
+ * core: The physical storage read cache can now be disabled via "disable_cache" [GH-674]
  * core: Tokens can now renew themselves [GH-455]
  * core: Base64-encoded PGP keys can be used with the CLI for `init` and `rekey` operations [GH-653]
  * logical: Responses now contain a "warnings" key containing a list of warnings returned from the server. These are conditions that did not require failing an operation, but of which the client should be aware. [GH-676]

command/server/config.go

@@ -18,6 +18,7 @@ type Config struct {
 	Listeners []*Listener `hcl:"-"`
 	Backend   *Backend    `hcl:"-"`
 
+	DisableCache bool `hcl:"disable_cache"`
 	DisableMlock bool `hcl:"disable_mlock"`
 
 	Telemetry *Telemetry `hcl:"telemetry"`
@@ -31,6 +32,7 @@ type Config struct {
 // DevConfig is a Config that is used for dev mode of Vault.
 func DevConfig() *Config {
 	return &Config{
+		DisableCache: false,
 		DisableMlock: true,
 
 		Backend: &Backend{
@@ -106,7 +108,12 @@ func (c *Config) Merge(c2 *Config) *Config {
 		result.Telemetry = c2.Telemetry
 	}
 
-	// merging this boolean via an OR operation
+	// merging these booleans via an OR operation
+	result.DisableCache = c.DisableCache
+	if c2.DisableCache {
+		result.DisableCache = c2.DisableCache
+	}
+
 	result.DisableMlock = c.DisableMlock
 	if c2.DisableMlock {
 		result.DisableMlock = c2.DisableMlock

command/server/config_test.go

@@ -36,6 +36,7 @@ func TestLoadConfigFile(t *testing.T) {
 			DisableHostname: false,
 		},
 
+		DisableCache: true,
 		DisableMlock: true,
 
 		MaxLeaseTTL:        10 * time.Hour,
@@ -128,6 +129,7 @@ func TestLoadConfigDir(t *testing.T) {
 	}
 
 	expected := &Config{
+		DisableCache: true,
 		DisableMlock: true,
 
 		Listeners: []*Listener{

command/server/test-fixtures/config-dir/foo.hcl

@@ -1,3 +1,4 @@
+disable_cache = true
 disable_mlock = true
 
 backend "consul" {

command/server/test-fixtures/config.hcl

@@ -1,3 +1,4 @@
+disable_cache = true
 disable_mlock = true
 statsd_addr = "bar"
 statsite_addr = "foo"

website/source/docs/config/index.html.md

@@ -42,6 +42,10 @@ to specify where the configuration is.
   "tcp" is currently the only option available. A full reference for the
    inner syntax is below.
 
+* `disable_cache` (optional) - A boolean. If true, this will disable the
+  read cache used by the physical storage subsystem. This will very
+  significantly impact performance.
+
 * `disable_mlock` (optional) - A boolean. If true, this will disable the
   server from executing the `mlock` syscall to prevent memory from being
   swapped to disk. This is not recommended in production (see below).