Database queries with Diesel (#192)

diesel.toml

@@ -0,0 +1,5 @@
+# For documentation on how to configure this file,
+# see diesel.rs/guides/configuring-diesel-cli
+
+[print_schema]
+file = "omicron-nexus/src/db/diesel_schema.rs"

omicron-common/Cargo.toml

@@ -6,6 +6,8 @@ edition = "2018"
 [dependencies]
 anyhow = "1.0"
 async-trait = "0.1.51"
+# Tracking pending 2.0 version.
+diesel = { git = "https://github.com/diesel-rs/diesel", rev = "a39dd2e", features = ["postgres", "r2d2", "chrono", "uuid"] }
 futures = "0.3.15"
 http = "0.2.0"
 hyper = "0.14"

omicron-common/src/api/external/error.rs

@@ -6,6 +6,8 @@
 
 use crate::api::external::Name;
 use crate::api::external::ResourceType;
+use diesel::result::DatabaseErrorKind as DieselErrorKind;
+use diesel::result::Error as DieselError;
 use dropshot::HttpError;
 use dropshot::HttpErrorResponseBody;
 use serde::Deserialize;
@@ -161,6 +163,46 @@ impl Error {
             },
         }
     }
+
+    /// Converts a Diesel error to an external type error.
+    pub fn from_diesel(
+        error: DieselError,
+        resource_type: ResourceType,
+        lookup_type: LookupType,
+    ) -> Error {
+        match error {
+            DieselError::NotFound => {
+                Error::ObjectNotFound { type_name: resource_type, lookup_type }
+            }
+            DieselError::DatabaseError(kind, _info) => {
+                Error::unavail(format!("Database error: {:?}", kind).as_str())
+            }
+            _ => Error::internal_error("Unknown diesel error"),
+        }
+    }
+
+    /// Converts a Diesel error to an external type error, when requested as
+    /// part of a creation operation.
+    pub fn from_diesel_create(
+        error: DieselError,
+        resource_type: ResourceType,
+        object_name: &str,
+    ) -> Error {
+        match error {
+            DieselError::DatabaseError(kind, _info) => match kind {
+                DieselErrorKind::UniqueViolation => {
+                    Error::ObjectAlreadyExists {
+                        type_name: resource_type,
+                        object_name: object_name.to_string(),
+                    }
+                }
+                _ => Error::unavail(
+                    format!("Database error: {:?}", kind).as_str(),
+                ),
+            },
+            _ => Error::internal_error("Unknown diesel error"),
+        }
+    }
 }
 
 impl From<Error> for HttpError {