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Database wraparound collector and test
Signed-off-by: Felix Yuan <[email protected]>
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‎collector/pg_database_wraparound.go

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// Copyright 2023 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package collector
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import (
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"context"
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"database/sql"
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"github.com/go-kit/log"
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"github.com/prometheus/client_golang/prometheus"
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)
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const databaseWraparoundSubsystem = "database_wraparound"
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func init() {
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registerCollector(databaseWraparoundSubsystem, defaultDisabled, NewPGDatabaseWraparoundCollector)
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}
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type PGDatabaseWraparoundCollector struct {
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log log.Logger
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}
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func NewPGDatabaseWraparoundCollector(config collectorConfig) (Collector, error) {
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return &PGDatabaseWraparoundCollector{log: config.logger}, nil
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}
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var (
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databaseWraparoundAgeDatfrozenxid = prometheus.NewDesc(
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prometheus.BuildFQName(namespace, databaseWraparoundSubsystem, "age_datfrozenxid_seconds"),
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"Age of the oldest transaction ID that has not been frozen.",
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[]string{"datname"},
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prometheus.Labels{},
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)
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databaseWraparoundAgeDatminmxid = prometheus.NewDesc(
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prometheus.BuildFQName(namespace, databaseWraparoundSubsystem, "age_datminmxid"),
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"Age of the oldest multi-transaction ID that has been replaced with a transaction ID.",
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[]string{"datname"},
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prometheus.Labels{},
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)
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databaseWraparoundQuery = `
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SELECT
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datname,
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age(d.datfrozenxid) as age_datfrozenxid,
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mxid_age(d.datminmxid) as age_datminmxid
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FROM
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pg_catalog.pg_database d
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WHERE
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d.datallowconn
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`
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)
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func (PGDatabaseWraparoundCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
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db := instance.getDB()
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rows, err := db.QueryContext(ctx,
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databaseWraparoundQuery)
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if err != nil {
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return err
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}
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defer rows.Close()
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for rows.Next() {
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var datname sql.NullString
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var ageDatfrozenxid, ageDatminmxid sql.NullFloat64
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if err := rows.Scan(&datname, &ageDatfrozenxid, &ageDatminmxid); err != nil {
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return err
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}
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datnameLabel := "unknown"
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if datname.Valid {
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datnameLabel = datname.String
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}
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ageDatfrozenxidMetric := 0.0
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if ageDatfrozenxid.Valid {
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ageDatfrozenxidMetric = ageDatfrozenxid.Float64
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}
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ch <- prometheus.MustNewConstMetric(
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databaseWraparoundAgeDatfrozenxid,
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prometheus.GaugeValue,
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ageDatfrozenxidMetric, datnameLabel,
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)
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ageDatminmxidMetric := 0.0
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if ageDatminmxid.Valid {
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ageDatminmxidMetric = ageDatminmxid.Float64
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}
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ch <- prometheus.MustNewConstMetric(
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databaseWraparoundAgeDatminmxid,
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prometheus.GaugeValue,
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ageDatminmxidMetric, datnameLabel,
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)
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}
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if err := rows.Err(); err != nil {
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return err
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}
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return nil
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}

‎collector/pg_database_wraparound_test.go

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// Copyright 2023 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package collector
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import (
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"context"
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"testing"
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"github.com/DATA-DOG/go-sqlmock"
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"github.com/prometheus/client_golang/prometheus"
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dto "github.com/prometheus/client_model/go"
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"github.com/smartystreets/goconvey/convey"
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)
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func TestPGDatabaseWraparoundCollector(t *testing.T) {
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db, mock, err := sqlmock.New()
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if err != nil {
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t.Fatalf("Error opening a stub db connection: %s", err)
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}
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defer db.Close()
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inst := &instance{db: db}
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columns := []string{
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"datname",
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"age_datfrozenxid",
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"age_datminmxid",
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}
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rows := sqlmock.NewRows(columns).
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AddRow("newreddit", 87126426, 0)
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mock.ExpectQuery(sanitizeQuery(databaseWraparoundQuery)).WillReturnRows(rows)
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ch := make(chan prometheus.Metric)
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go func() {
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defer close(ch)
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c := PGDatabaseWraparoundCollector{}
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if err := c.Update(context.Background(), inst, ch); err != nil {
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t.Errorf("Error calling PGDatabaseWraparoundCollector.Update: %s", err)
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}
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}()
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expected := []MetricResult{
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{labels: labelMap{"datname": "newreddit"}, value: 87126426, metricType: dto.MetricType_GAUGE},
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{labels: labelMap{"datname": "newreddit"}, value: 0, metricType: dto.MetricType_GAUGE},
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}
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convey.Convey("Metrics comparison", t, func() {
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for _, expect := range expected {
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m := readMetric(<-ch)
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convey.So(expect, convey.ShouldResemble, m)
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}
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})
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if err := mock.ExpectationsWereMet(); err != nil {
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t.Errorf("there were unfulfilled exceptions: %s", err)
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}
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}
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func TestPGDatabaseWraparoundCollectorNull(t *testing.T) {
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db, mock, err := sqlmock.New()
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if err != nil {
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t.Fatalf("Error opening a stub db connection: %s", err)
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}
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defer db.Close()
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inst := &instance{db: db}
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columns := []string{
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"datname",
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"age_datfrozenxid",
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"age_datminmxid",
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}
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rows := sqlmock.NewRows(columns).
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AddRow(nil, nil, nil)
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mock.ExpectQuery(sanitizeQuery(databaseWraparoundQuery)).WillReturnRows(rows)
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ch := make(chan prometheus.Metric)
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go func() {
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defer close(ch)
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c := PGDatabaseWraparoundCollector{}
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if err := c.Update(context.Background(), inst, ch); err != nil {
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t.Errorf("Error calling PGDatabaseWraparoundCollector.Update: %s", err)
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}
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}()
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expected := []MetricResult{
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{labels: labelMap{"datname": "unknown"}, value: 0, metricType: dto.MetricType_GAUGE},
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{labels: labelMap{"datname": "unknown"}, value: 0, metricType: dto.MetricType_GAUGE},
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}
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convey.Convey("Metrics comparison", t, func() {
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for _, expect := range expected {
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m := readMetric(<-ch)
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convey.So(expect, convey.ShouldResemble, m)
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}
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})
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if err := mock.ExpectationsWereMet(); err != nil {
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t.Errorf("there were unfulfilled exceptions: %s", err)
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}
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}

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