alistairjevans

lock(someSharedResource)
{
  // Do some work using the resource
  // and maybe update it.  
}

alistairjevans

public class LockModel
{        
    // We only need an ID right now
    public string Id { get; set; }
}

alistairjevans

 public class LockProvider
 {
  private readonly IMongoCollection<LockModel> collection;

  public LockProvider(string mongodbConnString) {} // Collapsed

  public async Task<IDisposable> AcquireLock(string resourceId)
  {
    // Determine the id of the lock
    var lockId = $"lock_{resourceId}";

alistairjevans

public class DistributedLock : IDisposable
{
  private readonly IMongoCollection<LockModel> collection;
  private readonly string lockId;

  public DistributedLock(IMongoCollection<LockModel> collection, string lockId)
  {
    this.collection = collection;
    this.lockId = lockId;
  }

alistairjevans

try
{
  var response = await collection.FindOneAndUpdateAsync<LockModel>( 
    // Collapsed  
  );

  // If the result of the FindOneAndUpdateAsync is null, then that means there was no record 
  // before we ran our statement, so we now have the lock.
  // If the result is not null, then it means a document for the lock already existed, so someone else has the lock.
  if (response == null)

alistairjevans

using (await LockProvider.AcquireLock(id))
{
  // Do some work
}

alistairjevans

public class LockModel
{        
    public string Id { get; set; }

    /// <summary>
    /// I'm going to set this to the moment in time when the lock should be cleared.
    /// </summary>
    public DateTime ExpireAt { get; set; }
}

alistairjevans

 var response = await collection.FindOneAndUpdateAsync<LockModel>(
  // Find a record with the lock ID
  x => x.Id == lockId,
  // If our 'upsert' creates a document, set the ID to the lock ID
  Builders<LockModel>.Update
    .SetOnInsert(x => x.Id, lockId)
    .SetOnInsert(x => x.ExpireAt, DateTime.UtcNow.AddMinutes(1)),
  new FindOneAndUpdateOptions<LockModel>
  {
    // If the record doesn't exist, create it.

alistairjevans

void setup()
{
  // Do your setup here,
  // configure your board, and so on.
}

void loop()
{
  // Called continuously. This is where you
  // will do the bulk of your work.

alistairjevans

void setup()
{
    // Configure the LED pin
    pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
    // Set the PIN to 'high'
    digitalWrite(LED_BUILTIN, HIGH);