Support missing samples in oximeter

- Add a `Datum::Missing` and `MissingDatum`, which records the intended datum type and an optional start time for a sample which could not be produced. - Database upgrades which make all scalar datum columns Nullable. Array fields are _not_ made Nullable, since ClickHouse doesn't support composite types like arrays inside a Nullable wrapper type. The empty array is used as a sentinel, which is OK since we can't have zero-length array histograms in Oximeter. Add a test which will fail if we ever change that. - Rework database serialization to handle Nullable types or empty arrays. This uses a new helper trait to convert a NULL (which has no type information) to the intended datum type, or an empty array to a histogram. - Add a test for each measurement type that we can recover a missing sample of that type -- NULLs for scalar values and empty arrays for histograms.
oxidecomputer · Nov 29, 2023 · e1f41f3 · e1f41f3
1 parent bb7ee84
commit e1f41f3
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Showing 61 changed files with 1,020 additions and 466 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/openapi/nexus-internal.json b/openapi/nexus-internal.json
@@ -2568,9 +2568,60 @@
               "datum",
               "type"
             ]
+          },
+          {
+            "type": "object",
+            "properties": {
+              "datum": {
+                "$ref": "#/components/schemas/MissingDatum"
+              },
+              "type": {
+                "type": "string",
+                "enum": [
+                  "missing"
+                ]
+              }
+            },
+            "required": [
+              "datum",
+              "type"
+            ]
           }
         ]
       },
+      "DatumType": {
+        "description": "The type of an individual datum of a metric.",
+        "type": "string",
+        "enum": [
+          "bool",
+          "i8",
+          "u8",
+          "i16",
+          "u16",
+          "i32",
+          "u32",
+          "i64",
+          "u64",
+          "f32",
+          "f64",
+          "string",
+          "bytes",
+          "cumulative_i64",
+          "cumulative_u64",
+          "cumulative_f32",
+          "cumulative_f64",
+          "histogram_i8",
+          "histogram_u8",
+          "histogram_i16",
+          "histogram_u16",
+          "histogram_i32",
+          "histogram_u32",
+          "histogram_i64",
+          "histogram_u64",
+          "histogram_f32",
+          "histogram_f64"
+        ]
+      },
       "DiskRuntimeState": {
         "description": "Runtime state of the Disk, which includes its attach state and some minimal metadata",
         "type": "object",
@@ -4128,9 +4179,77 @@
               "content",
               "type"
             ]
+          },
+          {
+            "type": "object",
+            "properties": {
+              "content": {
+                "type": "object",
+                "properties": {
+                  "datum_type": {
+                    "$ref": "#/components/schemas/DatumType"
+                  }
+                },
+                "required": [
+                  "datum_type"
+                ]
+              },
+              "type": {
+                "type": "string",
+                "enum": [
+                  "missing_datum_requires_start_time"
+                ]
+              }
+            },
+            "required": [
+              "content",
+              "type"
+            ]
+          },
+          {
+            "type": "object",
+            "properties": {
+              "content": {
+                "type": "object",
+                "properties": {
+                  "datum_type": {
+                    "$ref": "#/components/schemas/DatumType"
+                  }
+                },
+                "required": [
+                  "datum_type"
+                ]
+              },
+              "type": {
+                "type": "string",
+                "enum": [
+                  "missing_datum_cannot_have_start_time"
+                ]
+              }
+            },
+            "required": [
+              "content",
+              "type"
+            ]
           }
         ]
       },
+      "MissingDatum": {
+        "type": "object",
+        "properties": {
+          "datum_type": {
+            "$ref": "#/components/schemas/DatumType"
+          },
+          "start_time": {
+            "nullable": true,
+            "type": "string",
+            "format": "date-time"
+          }
+        },
+        "required": [
+          "datum_type"
+        ]
+      },
       "Name": {
         "title": "A name unique within the parent collection",
         "description": "Names must begin with a lower case ASCII letter, be composed exclusively of lowercase ASCII, uppercase ASCII, numbers, and '-', and may not end with a '-'. Names cannot be a UUID though they may contain a UUID.",

diff --git a/openapi/nexus.json b/openapi/nexus.json
@@ -9728,9 +9728,60 @@
               "datum",
               "type"
             ]
+          },
+          {
+            "type": "object",
+            "properties": {
+              "datum": {
+                "$ref": "#/components/schemas/MissingDatum"
+              },
+              "type": {
+                "type": "string",
+                "enum": [
+                  "missing"
+                ]
+              }
+            },
+            "required": [
+              "datum",
+              "type"
+            ]
           }
         ]
       },
+      "DatumType": {
+        "description": "The type of an individual datum of a metric.",
+        "type": "string",
+        "enum": [
+          "bool",
+          "i8",
+          "u8",
+          "i16",
+          "u16",
+          "i32",
+          "u32",
+          "i64",
+          "u64",
+          "f32",
+          "f64",
+          "string",
+          "bytes",
+          "cumulative_i64",
+          "cumulative_u64",
+          "cumulative_f32",
+          "cumulative_f64",
+          "histogram_i8",
+          "histogram_u8",
+          "histogram_i16",
+          "histogram_u16",
+          "histogram_i32",
+          "histogram_u32",
+          "histogram_i64",
+          "histogram_u64",
+          "histogram_f32",
+          "histogram_f64"
+        ]
+      },
       "DerEncodedKeyPair": {
         "type": "object",
         "properties": {
@@ -12250,6 +12301,22 @@
           "items"
         ]
       },
+      "MissingDatum": {
+        "type": "object",
+        "properties": {
+          "datum_type": {
+            "$ref": "#/components/schemas/DatumType"
+          },
+          "start_time": {
+            "nullable": true,
+            "type": "string",
+            "format": "date-time"
+          }
+        },
+        "required": [
+          "datum_type"
+        ]
+      },
       "Name": {
         "title": "A name unique within the parent collection",
         "description": "Names must begin with a lower case ASCII letter, be composed exclusively of lowercase ASCII, uppercase ASCII, numbers, and '-', and may not end with a '-'. Names cannot be a UUID though they may contain a UUID.",