Abstract: One or more computing devices, systems, and/or methods for monitoring levels of activity of client devices using a cluster of servers having a decentralized network architecture are provided, where over-counting, which may be caused by an uneven distribution of requests transmitted by the client devices to the cluster of servers, may be mitigated. For example, a request may be received by a first server, of the cluster of servers, from a client device. A first counter value associated with a level of activity of the client device may be incremented by a first number. One or more data packets may be transmitted to one or more servers of the cluster of servers. Each data packet of the one or more data packets may comprise an instruction to increment a counter value associated with the client device by a second number, which may be different than the first number.

Abstract: This disclosure describes a system and method for utilizing an automated aerial vehicle for determining the content of items included in bins within a materials handling facility. In some implementations, the automated aerial vehicle may fly along a flight path past one or more bins (e.g., for imaging the bins to determine the content of the bins and for which the images may be correlated with the bins). The flight path for the automated aerial vehicle may be determined based on various parameters e.g., for most efficiently imaging the bins, etc.).

Abstract: One or more computing devices, systems, and/or methods for monitoring levels of activity of client devices using a cluster of servers having a decentralized network architecture are provided, where over-counting, which may be caused by an uneven distribution of requests transmitted by the client devices to the cluster of servers, may be mitigated. For example, a request may be received by a first server, of the cluster of servers, from a client device. A first counter value associated with a level of activity of the client device may be incremented by a first number. One or more data packets may be transmitted to one or more servers of the cluster of servers. Each data packet of the one or more data packets may comprise an instruction to increment a counter value associated with the client device by a second number, which may be different than the first number.

Abstract: One or more computing devices, systems, and/or methods for monitoring levels of activity of client devices using a cluster of servers having a decentralized network architecture are provided, where over-counting, which may be caused by an uneven distribution of requests transmitted by the client devices to the cluster of servers, may be mitigated. For example, a request may be received by a first server, of the cluster of servers, from a client device. A first counter value associated with a level of activity of the client device may be incremented by a first number. One or more data packets may be transmitted to one or more servers of the cluster of servers. Each data packet of the one or more data packets may comprise an instruction to increment a counter value associated with the client device by a second number, which may be different than the first number.

Abstract: One or more computing devices, systems, and/or methods for monitoring levels of activity of client devices using a cluster of servers having a decentralized network architecture are provided, where over-counting, which may be caused by an uneven distribution of requests transmitted by the client devices to the cluster of servers, may be mitigated. For example, a request may be received by a first server, of the cluster of servers, from a client device. A first counter value associated with a level of activity of the client device may be incremented by a first number. One or more data packets may be transmitted to one or more servers of the cluster of servers. Each data packet of the one or more data packets may comprise an instruction to increment a counter value associated with the client device by a second number, which may be different than the first number.

Abstract: Techniques described and suggested include systems, methods, and processes for determining data-related attributes, such as size, for data and/or data containers (such as volumes and file systems) resident on distributed storage systems. For example, a shared records storage device may be utilized to gather information related to file systems stored on a distributed storage system having a plurality of storage servers. A data processor may be used to generate information records and meter data storage size for file systems resident on the distributed storage system, and such records may be provided to requestors, such as customers associated with the file systems.

Abstract: One or more computing devices, systems, and/or methods for verifying a user of a service are provided. That is, the service (e.g., a social network, an email service, a website, etc.) may attempt to verify that a user is an owner of an account with the service by sending a verification code to a device registered by the user with the service, such as through a text message. Because the service may be hosted across multiple data centers for resiliency against failure, the verification code and a verification attempt counter may be stored within a particular data store. An identification of the data store may be encoded into the verification code. In this way, the verification code may be sent to the device, such that when the user submits the verification code back to the service, the verification code is routed to the correct data store for verification.

Abstract: A client request, formatted in accordance with a file system interface, is received at an access subsystem of a distributed multi-tenant storage service. After the request is authenticated at the access subsystem, an atomic metadata operation comprising a group of file system metadata modifications is initiated, including a first metadata modification at a first node of a metadata subsystem of the storage service and a second metadata modification at a second node of the metadata subsystem. A plurality of replicas of at least one data modification corresponding to the request are saved at respective storage nodes of the service.

Abstract: This disclosure describes a system and method for utilizing an automated aerial vehicle for determining the content of items included in bins within a materials handling facility. In some implementations, the automated aerial vehicle may fly along a flight path past one or more bins and capture images of those bins. The images may be processed to determine the content of the bins, and other images of areas outside of the bins may also be processed (e.g., for detecting items on floors, security issues, etc.). The flight path for the automated aerial vehicle may be determined and/or modified based on various parameters (e.g., to most efficiently capture the images of the bins, to temporarily avoid areas with obstacles, etc.).

Abstract: This disclosure describes a system and method for utilizing an automated aerial vehicle for determining the content of items included in bins within a materials handling facility. In some implementations, the automated aerial vehicle may fly along a flight path past one or more bins and capture images of those bins. The images may be processed to determine the content of the bins, and other images of areas outside of the bins may also be processed (e.g., for detecting items on floors, security issues, etc.). The flight path for the automated aerial vehicle may be determined and/or modified based on various parameters (e.g., to most efficiently capture the images of the bins, to temporarily avoid areas with obstacles, etc.).

Abstract: Techniques described and suggested include systems, methods, and processes for determining data-related attributes, such as size, for data and/or data containers (such as volumes and file systems) resident on distributed storage systems. For example, a shared records storage device may be utilized to gather information related to file systems stored on a distributed storage system having a plurality of storage servers. A data processor may be used to generate information records and meter data storage size for file systems resident on the distributed storage system, and such records may be provided to requestors, such as customers associated with the file systems.

Abstract: In response to receiving a write request directed to a particular logical block of a storage object, a page of free space (sufficient to accommodate the payload of the write request, but smaller in size than the logical block) of a particular extent that has been selected to store contents of the logical block is allocated. The current size of the extent is smaller than the combined sizes of logical blocks that are mapped to the extent. The page is modified in accordance with a payload indicated in the write request. In response to a subsequent write request directed to the particular extent, a determination is made that the particular extent would violate a free space threshold criterion if the payload of the write request were accommodated, and an extent expansion operation is initiated.

Abstract: A write request directed to a storage object is received at a distributed file storage service. Based on a variable stripe size selection policy, a size of a particular stripe of storage space to be allocated for the storage object is determined, which differs from the size of another stripe allocated earlier for the same storage object. Allocation of storage for the particular stripe at a particular storage device is requested, and if the allocation succeeds, the contents of the storage device are modified in accordance with the write request.

Abstract: Techniques described and suggested include systems, methods, and processes for determining data-related attributes, such as size, for data and/or data containers (such as volumes and file systems) resident on distributed storage systems. For example, a shared records storage device may be utilized to gather information related to file systems stored on a distributed storage system having a plurality of storage servers. A data processor may be used to generate information records and meter data storage size for file systems resident on the distributed storage system, and such records may be provided to requestors, such as customers associated with the file systems.

Abstract: An I/O request directed to a portion of a storage object managed at a distributed storage service is received. A congestion control parameter value to be used to schedule a storage operation corresponding to the I/O request is determined. The congestion control parameter is based at least in part on an offset within the storage object to which the I/O request is directed. The storage operation is scheduled in accordance with the congestion control parameter at a selected physical storage device to which the portion of the storage object is mapped.

Abstract: One or more computing devices, systems, and/or methods for verifying a user of a service are provided. That is, the service (e.g., a social network, an email service, a website, etc.) may attempt to verify that a user is an owner of an account with the service by sending a verification code to a device registered by the user with the service, such as through a text message. Because the service may be hosted across multiple data centers for resiliency against failure, the verification code and a verification attempt counter may be stored within a particular data store. An identification of the data store may be encoded into the verification code. In this way, the verification code may be sent to the device, such that when the user submits the verification code back to the service, the verification code is routed to the correct data store for verification.

Abstract: A connection request from a client is received at an access subsystem node of a distributed storage service. The connection request includes an attempt count parameter indicative of a number of times an establishment of a connection on behalf of the client has been attempted. A workload threshold level based on the attempt count parameter is identified for use in an acceptance decision for the connection request. In response to a determination that a local workload metric of the access subsystem node is below the workload threshold level, the connection is accepted.

Abstract: A node of a distributed storage service receives a read request from a client, directed to a particular physical page storing at least a portion of a file store object. The node transmits, to the client, a particular operation sequence number (OSN), obtained from a replicated state machine, indicative of an order in which the read request was processed at the node relative to other requests directed to the file store object. The node receives a write request from the client directed to the page. The write request includes the particular OSN. The node determines whether the page has been modified after the particular OSN was obtained. If the page has not been modified since the OSN was obtained, a modification indicated in the write request is performed; otherwise, the write request is rejected.

Abstract: A node of a storage service is selected as a coordinator of a distributed transaction involving multiple page-level modifications. The coordinator identifies other nodes as members of a node chain collectively storing physical data pages at which proposed modifications are to be performed, including a decider node responsible for a decision to commit the transaction. The coordinator generates a transaction preparation message comprising a representation of an order of respective commit decisions associated with the proposed modifications, and transmits the message to a selected node of the chain for a sequential propagation along the chain. Each chain node performs a local commit analysis for its changes and stores a record of its intent to commit. If a decision to commit is reached at the decider, the proposed modifications are completed.

Abstract: A directed acyclic graph (DAG) is generated to represent a namespace of a directory. In response to a request to create a new object with a specified name, a hash value bit sequence is computed for the name. A plurality of levels of the DAG are navigated using successive subsequences of the bit sequence to identify a candidate node for storing a new entry corresponding to the specified name. If the candidate node meets a split criterion, the new entry and at least a selected subset of entries of the candidate node's list of entries are distributed among a plurality of DAG nodes, including at least one new DAG node, using respective bit sequences obtained by applying the hash function for each distributed entry.