// readSkews reads all clock data for the client's namespace.
func (client *client) readSkews(collection mongo.Collection) (map[string]Skew, error) {
// Read the clock document, recording the time before and after completion.
readBefore := client.config.Clock.Now()
var clockDoc clockDoc
if err := collection.FindId(client.clockDocId()).One(&clockDoc); err != nil {
return nil, errors.Trace(err)
}
readAfter := client.config.Clock.Now()
if err := clockDoc.validate(); err != nil {
return nil, errors.Annotatef(err, "corrupt clock document")
}
// Create skew entries for each known writer...
skews, err := clockDoc.skews(readBefore, readAfter)
if err != nil {
return nil, errors.Trace(err)
}
// If a writer was previously known to us, and has not written since last
// time we read, we should keep the original skew, which is more accurate.
for writer, skew := range client.skews {
if skews[writer].LastWrite == skew.LastWrite {
skews[writer] = skew
}
}
// ...and overwrite our own with a zero skew, which will DTRT (assuming
// nobody's reusing client ids across machines with different clocks,
// which *should* never happen).
skews[client.config.Id] = Skew{}
return skews, nil
}
// exists returns whether the identified refcount doc exists.
func (nsRefcounts_) exists(coll mongo.Collection, key string) (bool, error) {
count, err := coll.FindId(key).Count()
if err != nil {
return false, errors.Trace(err)
}
return count != 0, nil
}
// read returns the value stored in the identified refcount doc.
func (nsRefcounts_) read(coll mongo.Collection, key string) (int, error) {
var doc refcountDoc
if err := coll.FindId(key).One(&doc); err == mgo.ErrNotFound {
return 0, errors.NotFoundf("refcount %q", key)
} else if err != nil {
return 0, errors.Trace(err)
}
return doc.RefCount, nil
}
// setStatusOp returns a txn.Op that updates the status of the
// identified payload. If the payload doesn't exist, it returns
// errAlreadyRemoved.
func (nsPayloads_) setStatusOp(payloads mongo.Collection, docID string, status string) (txn.Op, error) {
count, err := payloads.FindId(docID).Count()
if err != nil {
return txn.Op{}, errors.Trace(err)
} else if count == 0 {
return txn.Op{}, errAlreadyRemoved
}
return txn.Op{
C: payloads.Name(),
Id: docID,
Assert: txn.DocExists,
Update: bson.D{{"$set", bson.D{{"state", status}}}},
}, nil
}
// untrackOp returns a txn.Op that will unconditionally remove the
// identified document. If the payload doesn't exist, it returns
// errAlreadyRemoved.
func (nsPayloads_) untrackOp(payloads mongo.Collection, docID string) (txn.Op, error) {
count, err := payloads.FindId(docID).Count()
if err != nil {
return txn.Op{}, errors.Trace(err)
} else if count == 0 {
return txn.Op{}, errAlreadyRemoved
}
return txn.Op{
C: payloads.Name(),
Id: docID,
Assert: txn.DocExists,
Remove: true,
}, nil
}
// trackOp returns a txn.Op that will either insert or update the
// supplied payload, and fail if the observed precondition changes.
func (nsPayloads_) trackOp(payloads mongo.Collection, doc payloadDoc) (txn.Op, error) {
docID := nsPayloads.docID(doc.UnitID, doc.Name)
payloadOp := txn.Op{
C: payloads.Name(),
Id: docID,
}
count, err := payloads.FindId(docID).Count()
if err != nil {
return txn.Op{}, errors.Trace(err)
} else if count == 0 {
payloadOp.Assert = txn.DocMissing
payloadOp.Insert = doc
} else {
payloadOp.Assert = txn.DocExists
payloadOp.Update = bson.D{{"$set", doc}}
}
return payloadOp, nil
}