RMW pattern described in Understanding Aerospike Transactions blog post

gistfile1.txt

# R-M-W pattern pseudo-code for a read-write transaction

Result RMWTransaction(key, read_bins, update_func):
   # key:       key tuple (namespace, set, id)
   # read_bins: list of bins to read
   # update_func: update function that takes a map read_bins->
   #             values and returns a map write_bins->values
   # Result:    return enum that includes Success and Retry

   # 1. Read the record
   read_policy = [{'read_mode_sc': SC_LINEARIZE}]
   record = Aerospike.get(read_policy, key, read_bins)
   read_generation = record.generation

   # 2. Modify the record
   read_bin_vals = {}
   for read_bin in read_bins:
       read_bin_vals[read_bin] = record[read_bin]
   write_bin_vals = update_func(read_bin_vals)

   # 3. Prepare write with generation comparison and no retries.
   write_policy = { 'generation_policy': GEN_EQUAL,
                   'generation': read_generation,
                   'max_retries': 0 }

   # 4. Write the modified data
   ops = []
   for write_bin, write_val in write_bin_vals:
       ops.append({'op': WRITE, 'bin': write_bin, 'val': write_val})
   try:
       Aerospike.operate(write_policy, key, ops)
   catch GENERATION_ERROR:
       # retry on generation error
       return Retry

   return Success