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Building high throughput permissioned blockchain fabrics: challenges and opportunities

Building High Throughput Permissioned Blockchain
Fabrics: Challenges and Opportunities
Suyash Gupta, Jelle Hellings, Sajjad Rahnama, Mohammad Sadoghi
Exploratory Systems Lab, Department of Computer Science
University of California, Davis, CA 95616-8562, USA
Since the introduction of Bitcoin—the first widespread ap-
plication driven by blockchains—the interest in the design of
blockchain-based applications has increased tremendously.
At the core of these applications are consensus protocols
that securely replicate client requests among all replicas,
even if some replicas are Byzantine faulty. Unfortunately,
these consensus protocols typically have low throughput,
and this lack of performance is often cited as the reason
for the slow wider adoption of blockchain technology. Con-
sequently, many works focus on designing more efficient con-
sensus protocols to increase throughput of consensus.
We believe that this focus on consensus protocols only ex-
plains part of the story. To investigate this belief, we raise
a simple question: Can a well-crafted system using a clas-
sical consensus protocol outperform systems using modern
protocols? In this tutorial, we answer this question by div-
ing deep into the design of blockchain systems. Further, we
take an in-depth look at the theory behind consensus, which
can help users select the protocol that best-fits their re-
quirements. Finally, we share our vision of high-throughput
blockchain systems that operate at large scales.
PVLDB Reference Format:
Suyash Gupta, Jelle Hellings, Sajjad Rahnama and Mohammad
Sadoghi. Building High Throughput Permissioned Blockchain
Fabrics: Challenges and Opportunities. PVLDB, 13(12): 3441-
3444, 2020.
Since the introduction of Bitcoin—the first wide-spread
application driven by blockchain—the interest in the de-
sign of blockchain-based applications has increased tremen-
dously. This interest has resulted in several blockchain-
inspired fabrics and database systems [2, 3, 17, 27, 39, 40].
Further, blockchain-based systems have been employed to
address challenges in various other fields such as food pro-
duction, managing land property rights, energy trading, and
managing identities.
This work is licensed under the Creative Commons Attribution-
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Proceedings of the VLDB Endowment, Vol. 13, No. 12
ISSN 2150-8097.
At the core of these blockchain applications are Byzantine-
Fault Tolerant (BFT) consensus protocols that ensures all
replicas of this blockchain application reach consensus on
the ordering of incoming client request, this even if some of
the replicas are Byzantine [8, 24, 27, 34, 45].
A decade after the introduction of blockchains in crypto-
currencies and after several prominent research projects, we
see that crypto-currencies are still the major known use-
cases of blockchains. This raises a key question: Why have
blockchain applications seen such a slow wider adoption?
The low throughput and high latency of BFT consensus
are cited as key reasons for this. Prior works have shown
that traditional distributed databases can achieve through-
puts of the order 100 K transactions per second [29, 30],
while initial permissionless blockchain applications such as
Bitcoin [38] and Ethereum [44] have throughputs of only
a few transactions per second. In these crypto-currency
applications, low throughputs are seen as acceptable, as
these costly techniques enable a fully decentralized currency
that is not controlled by a single government or corpora-
tion. Indeed, crypto-currency blockchains typically have
open-membership, as anyone can join these blockchains.
Although permissionless blockchains highlight the notions
of decentralization and resilience, their open-membership
is often unnecessary for fault-tolerant transaction process-
ing. This led to the design of industry-grade permissioned
blockchains, where only a select group of users, some of
which may be untrusted, can participate [3]. These permis-
sioned designs employ traditional BFT consensus to provide
throughputs of up-to 10 K transactions per second [2, 3],
which is still short of the performance expected of modern
systems. Several prior works [9, 11, 34, 45] blame the low
throughput and scalability of permissioned blockchains on
the underlying BFT consensus. Although these claims are
not false, they only explain part of the story. From our per-
spective, permissioned blockchain applications can achieve
wider adoption by improving in three vital directions.
First, it is well-known that an efficient protocol may not
always lead to a high-throughput implementation. The same
principle applies to consensus protocols used in existing per-
missioned blockchain fabrics. Although these fabrics provide
platforms to employ blockchains in various use-cases, these
fabrics fall short in their architectural details [2, 3, 6, 21].
We claim that the low throughput of these fabrics is due
to missed opportunities during their design and implemen-
tation. Indeed, a well-crafted blockchain fabric can have
an order-of-magnitude increase in its throughput, e.g., by
exploiting parallelization and pipelining opportunities.
Second, the full replication employed by current block-
chain applications stands in their way of achieving ever-
higher performance. To make blockchains more usable, their
design needs to evolve to incorporate sharding and special-
ization. To support such designs, new resilient techniques
besides consensus need to be developed.
Finally, permissioned blockchain systems need tuning to
specific settings. E.g., blockchains can be used for feder-
ated data management, the collective management of a single
database among various stakeholders. Federated data man-
agement is in itself a major step towards dealing with data
quality issues arising from the non-federated interchange of
information between various stakeholders and, as such, can
reduce the huge negative economic impact of bad data [16,
33, 42]. In federated data management, resilience is less of a
priority, and the focus of such blockchain systems is on fast
data update and retrieval, efficient query processing, and
modular data analysis.
In this tutorial, we will provide a deep dive into consen-
sus protocols with a focus on data management. To do so,
we take an in-depth look at Byzantine fault-tolerant con-
sensus protocols, the main technique powering permissioned
blockchains. The tutorial is intended for an audience that
has prior knowledge of databases and will be of interest to
both theoreticians and practitioners who want to employ
blockchain concepts to their work.
This tutorial starts with a general-purpose introduction to
blockchains from the perspective of data management. Fol-
lowing the introduction, the tutorial will focus on three av-
enues. First, we look at the theoretical framework in which
permissioned blockchains operate. Then, we look at prac-
tical high-performance consensus protocols and at current
developments. This theoretical framework provides users of
a permissioned blockchain system with the right tools to se-
lect the consensus protocols that best-fits their requirements.
Second, we look at the architectural challenges in the de-
sign of high-performance permissioned blockchain systems,
in which we show how existing principles of thread paral-
lelization and task pipelining can be applied to blockchain
fabrics. Further, we illustrate ways to optimize data access
and query processing in permissioned blockchain applica-
tions. Finally, we look at the design challenges for high-
performance permissioned blockchain systems of the future
that can deal with huge amounts of data. We conclude by
presenting our vision on future developments. Next, we ex-
plain these three avenues in detail.
BFT Consensus Protocols. Blockchains are, at their ba-
sis, fully replicated distributed systems that aim to main-
tain data consistency. The well-known CAP Theorem puts
restrictions on the types of failures these blockchains can
deal with while guaranteeing continued services [7, 20]. The
CAP Theorem puts rather general limitations on the design
of blockchains, however. More specific limitations are also
known, as the Byzantine consensus problem and other re-
lated problems, such as the Byzantine agreement problem
and the interactive consistency problem, have received con-
siderable attention.
It is well-known that the Byzantine agreement problem
can only be solved when using synchronous communica-
tion [19, 37, 43]. In a synchronous environment with n
4 8 16 32
Number of replicas (n)
Throughput (txn/s)
Figure 1: Two permissioned applications employing
distinct BFT protocols.
replicas of which fare Byzantine (e.g., malicious), Byzan-
tine agreement requires that n>3f[12, 13]. When strong
cryptographic primitives are available, this can be improved
to n>f[15, 35, 41] (although practical systems will still re-
quire n>2f). Additionally, bounds on the amount of com-
munication and the quality of the network are known [10,
12, 13, 14, 15, 18].
Having provided a theoretical background, we take a step
towards detailing practical consensus protocols. We do so
by a full coverage of the Practical Byzantine Fault Tolerance
consensus protocol (Pbft) of Castro et al. [8]. Next, we also
look at the lineage of consensus protocols that refine and im-
prove Pbft. This detailed overview will cover many of the
practical consensus protocols currently in use and, simulta-
neously, also covers recent developments. Our coverage will
include protocols such as Pbft, HotStuff [45], Zyzzyva [4,
34], FaB [36], SynBFT [1], RBFT [5], PoE [23], and Multi-
BFT [24, 25]. All of these protocols make some tradeoffs
and, hence, achieve optimal throughput only under specific
conditions. In our tutorial, we will discuss these tradeoffs
and conditions in detail, as this enables one to select the
protocol that best-fits the requirements of their particular
blockchain application.
Architectural Paradigm. Although an efficient consensus
protocol can help increase the throughput of the associated
permissioned blockchain application, the design of the sys-
tem and its implementation matters equally. In our tutorial,
we will show that classical BFT protocols that are perceived
to be slow such as Pbft [8] can always outperform niche-
case optimized BFT protocols such as Zyzzyva [34] if im-
plemented in a well-designed and skillfully-optimized block-
chain fabric. We use Figure 1 to illustrate such a possibility.
In this figure, we measure the throughput of ResilientDB,
our permissioned blockchain system [27, 28], and intention-
ally make it employ the “slow” Pbft protocol. Next, we
compare the throughput of ResilientDB against a permis-
sioned blockchain system that adopts practices suggested
in BFTSmart [6], and employs the fast Zyzzyva protocol.
We observe that the system-centric design of ResilientDB
can use the costly three-phase Pbft protocol (of which two
phases require quadratic communication among replicas),
while still outperforming systems utilizing Zyzzyva (a single-
phase protocol with linear communication among replicas).
Decades of academic research [29, 30] have helped the
community in designing efficient distributed databases and
applications. In this tutorial, we study existing practices
to design an optimal permissioned blockchain fabric. These
practices include the use of speculation [34, 36], execute-
order or order-execute paradigms [3], component modular-
ity [6], transaction batching or streaming [2, 11], and out-of-
order message processing [28]. Further, we will discuss how
data storage, data maintenance, data retrieval, and NoSQL
and relational database support is provided by our state-of-
the-art permissioned blockchain fabrics [28]. We will demon-
strate this functionality via a user interface that can ease
query processing and data analysis.
Challenges and our Vision. As outlined above, the key
component of any permissionless and permissioned block-
chain remains the underlying BFT consensus protocol that
provides reliable replication. Unfortunately, these protocols
are challenged by the scalability and performance required
by many modern big-data-driven applications. In specific,
we see that there is no obvious way to scale up BFT con-
sensus: adding more replicas will only increase the cost of
replication and decrease the throughput of the system, even
when using the most efficient consensus protocols.
We will close our tutorial by discussing recent steps to-
ward the design of new fault-tolerant architectures that step
away from the full-replicated nature of blockchains, this to
increase scalability and the ability to serve big-data-driven
applications. To put our vision in practice, we will first look
at two low-level techniques, cluster-sending [31] and delayed-
replication [32]. Next, we look at high-level designs enabled
by these techniques to provide high-performance parallelized
consensus [24, 25] and to provide high-performance consen-
sus in sharded and geo-scale aware architectures [27].
Suyash Gupta is a Ph.D. Candidate at the Computer
Science Department at University of California, Davis. At
UC Davis, he is a senior member of Exploratory Systems
Lab and works under the supervision of Prof. Sadoghi. He
also works as the Lead Architect at the blockchain company
Moka Blox and ResilientDB. He also holds a Master of Sci-
ence degree from Purdue University and a Master of Sci-
ence (Research) degree from Indian Institute of Technology
Madras. His current research focuses on attaining safe and
efficient fault-tolerant consensus in distributed and block-
chain systems. He also has published works that present
efficient compiler optimizations and designs for parallel and
distributed algorithms.
Jelle Hellings finished his graduate studies at the Eind-
hoven University of Technology, Netherlands in 2011, with
a final research project focused on external memory algo-
rithms for indexing trees and directed acyclic graphs. He
then moved to Hasselt University, Belgium, where he did
his doctoral research in the Databases and Theoretical Com-
puter Science research group. He finished his doctoral re-
search on the expressive power of query languages in 2018.
Since the summer of 2018, Jelle is a Postdoc Fellow at UC
Davis in the Exploratory Systems Lab led by Prof. Sadoghi.
His current research focus is on the theoretical bounds of
consensus protocols in malicious environments and, more
general, on exploring new directions for replicated systems
in malicious environment.
Sajjad Rahnama is a Ph.D. student at the Computer
Science Department of the University of California Davis
supervised by Prof. Sadoghi. He is also a member of Ex-
ploratory Systems Lab. He also works as the System De-
signer at the blockchain company called Moka Blox and is
the main developer for ResilientDB. His current research fo-
cuses on secure transaction processing and designing global-
scale fault-tolerant protocols, distributed systems, and their
applications in blockchain. He holds a B.Sc. in Computer
Science from Amirkabir University of Technology, Tehran,
Iran. Prior to starting his Ph.D., he worked in several tech
companies as a infrastructure engineer and developer.
Mohammad Sadoghi is an Assistant Professor in the
Computer Science Department at UC Davis. He leads the
ExpoLab research group with the aim to pioneer a dis-
tributed ledger that unifies secure transactional and real-
time analytical processing (L-Store), all centered around
a democratic and decentralized computational model (Re-
silientDB). He has co-founded a blockchain company called
Moka Blox LLC, a ResilientDB spin-off. He has over 80
publications in leading database conferences/journals and
34 filed U.S. patents. He has co-authored a book enti-
tled “Transaction Processing on Modern Hardware”, Mor-
gan & Claypool Synthesis Lectures on Data Management,
and currently co-authoring a book entitled “Fault-tolerant
Distributed Transactions on Blockchain”, Morgan & Clay-
pool series.
This tutorial is based on the outline of our upcoming book
on fault-tolerant transaction processing on blockchains [26].
Furthermore, this tutorial is an evolution of a tutorial pre-
sented at Middleware 2019 [22]. We have updated that tu-
torial with new and upcoming techniques and insights.
This work is partially supported by the U.S. Department
of Energy, Office of Science, Office of Small Business Inno-
vation Research, under Award Number DE-SC0020455.
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... The RESILIENTDB fabric incorporates secure permissioned blockchain technologies to provide resilient data processing. A detailed description of how RESILIENTDB achieves highthroughput consensus in a practical settings can be found in Gupta et al. [21], [29], [30], [31], [32]. The architecture of RESILIENTDB is optimized for maximizing throughput via multi-threading and pipelining. ...
... In permissioned blockchain, such as Hyperledger Fabric, only identified users can validate transactions and access block data (Cachin, 2016). Permissionless blockchain highlights openness and decentralization, while permissioned blockchain can provide higher 120 throughputs by designing deterministic consensus protocols (Gupta et al., 2020). Therefore, permissioned blockchains are more applicable for time-sensitive CSCM applications in terms of transparency, traceability, immutability, decentralization, privacy, and smartness (Qian and Papadonikolaki, 2020). ...
Blockchain technology has attracted the interest of the global construction industry for its potential to enhance the transparency, traceability, and immutability of construction data and enables collaboration and trust throughout the supply chain. However, such potential cannot be achieved without blockchain "oracles" needed to bridge the on-chain (i.e., blockchain system) and off-chain (i.e., real-life physical project) worlds. This study presents an innovative solution that exploits smart construction objects (SCOs). It develops a SCOs-enabled blockchain oracles (SCOs-BOs) framework. To instantiate this framework, the system architecture of a blockchain-enabled construction supply chain management (BCSCM) system is developed and validated using a case study, whereby four primary smart contracts are examined in the context of off-site logistics and on-site assembly services. The validation results show that accurate data is retrieved against malicious data in each request, and the corresponding reputation scores are successfully recorded. The innovativeness of the research lies in two aspects. In addition to mobilizing SCOs as blockchain oracles to bridge the on-chain and off-chain worlds, it develops a decentralized SCO network to avoid the single point of failure (SPoF) problem widely existing in blockchain systems. This study contributes to existing research and practice to harness the power of blockchain in construction.
... This tutorial also differs from C. Mohan's tutorial at VLDB 2017 [45] and ICDE 2018 [46] where he explicitly states that the scope of his tutorial "is general in nature without getting into the nitty gritty of, e.g., cryptographic algorithms or the distributed consensus protocols". Finally, this tutorial is different from the tutorial presented by Gupta et al. [30] at VLDB 2020 where the focus of that tutorial was on exploring high throughput consensus protocols for permissioned blockchains. ...
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Since the introduction of Bitcoin—the first widespread application driven by blockchain—the interest of the public and private sectors in blockchain has skyrocketed. In recent years, blockchain-based fabrics have been used to address challenges in diverse fields such as trade, food production, property rights, identity-management, aid delivery, health care, and fraud prevention. This widespread interest follows from fundamental concepts on which blockchains are built that together embed the notion of trust, upon which blockchains are built. 1. Blockchains provide data transparency. Data in a blockchain is stored in the form of a ledger, which contains an ordered history of all the transactions. This facilitates oversight and auditing. 2. Blockchains ensure data integrity by using strong cryptographic primitives. This guarantees that transactions accepted by the blockchain are authenticated by its issuer, are immutable, and cannot be repudiated by the issuer. This ensures accountability. 3. Blockchains are decentralized, democratic, and resilient. They use consensus-based replication to decentralize the ledger among many independent participants. Thus, it can operate completely decentralized and does not require trust in a single authority. Additions to the chain are performed by consensus, in which all participants have a democratic voice in maintaining the integrity of the blockchain. Due to the usage of replication and consensus, blockchains are also highly resilient to malicious attacks even when a significant portion of the participants are malicious. It further increases the opportunity for fairness and equity through democratization. These fundamental concepts and the technologies behind them—a generic ledger-based data model, cryptographically ensured data integrity, and consensus-based replication—prove to be a powerful and inspiring combination, a catalyst to promote computational trust. In this book, we present an in-depth study of blockchain, unraveling its revolutionary promise to instill computational trust in society, all carefully tailored to a broad audience including students, researchers, and practitioners. We offer a comprehensive overview of theoretical limitations and practical usability of consensus protocols while examining the diverse landscape of how blockchains are manifested in their permissioned and permissionless forms.
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We present HotStuff, a leader-based Byzantine fault-tolerant replication protocol for the partially synchronous model. Once network communication becomes synchronous, HotStuff enables a correct leader to drive the protocol to consensus at the pace of actual (vs. maximum) network delay--a property called responsiveness---and with communication complexity that is linear in the number of replicas. To our knowledge, HotStuff is the first partially synchronous BFT replication protocol exhibiting these combined properties. Its simplicity enables it to be further pipelined and simplified into a practical, concise protocol for building large-scale replication services.
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The last fifteen years have seen an impressive amount of work on protocols for Byzantine fault-tolerant (BFT) state machine replication (SMR). However, there is still a need for practical and reliable software libraries implementing this technique. BFT-SMART is an open-source Java-based library implementing robust BFT state machine replication. Some of the key features of this library that distinguishes it from similar works (e.g., PBFT and UpRight) are improved reliability, modularity as a first-class property, multicore-awareness, reconfiguration support and a flexible programming interface. When compared to other SMR libraries, BFT-SMART achieves better performance and is able to withstand a number of real-world faults that previous implementations cannot.
In this paper, we design and implement the first-ever decentralized replicated relational database with blockchain properties that we term blockchain relational database. We highlight several similarities between features provided by blockchain platforms and a replicated relational database, although they are conceptually different, primarily in their trust model. Motivated by this, we leverage the rich features, decades of research and optimization, and available tooling in relational databases to build a blockchain relational database. We consider a permissioned blockchain model of known, but mutually distrustful organizations each operating their own database instance that are replicas of one another. The replicas execute transactions independently and engage in decentralized consensus to determine the commit order for transactions. We design two approaches, the first where the commit order for transactions is agreed upon prior to executing them, and the second where transactions are executed without prior knowledge of the commit order while the ordering happens in parallel. We leverage serializable snapshot isolation (SSI) to guarantee that the replicas across nodes remain consistent and respect the ordering determined by consensus, and devise a new variant of SSI based on block height for the latter approach. We implement our system on PostgreSQL and present detailed performance experiments analyzing both approaches.
Despite recent intensive research, existing blockchain systems do not adequately address all the characteristics of distributed applications. In particular, distributed applications collaborate with each other following service level agreements (SLAs) to provide different services. While collaboration between applications, e.g., cross-application transactions, should be visible to all applications, the internal data of each application, e.g, internal transactions, might be confidential. In this paper, we introduce CAPER, a permissioned blockchain system to support both internal and cross-application transactions of collaborating distributed applications. In CAPER, the blockchain ledger is formed as a directed acyclic graph where each application accesses and maintains only its own view of the ledger including its internal and all cross-application transactions. CAPER also introduces three consensus protocols to globally order cross-application transactions between applications with different internal consensus protocols. The experimental results reveal the efficiency of CAPER in terms of performance and scalability.
In this paper we present BlockchainDB, which leverages blockchains as a storage layer and introduces a database layer on top that extends blockchains by classical data management techniques (e.g., sharding) as well as a standardized query interface to facilitate the adoption of blockchains for data sharing use cases. We show that by introducing the additional database layer, we are able to improve the performance and scalability when using blockchains for data sharing and also massively decrease the complexity for organizations intending to use blockchains for data sharing.
Blockchain technologies are gaining massive momentum in the last few years. Blockchains are distributed ledgers that enable parties who do not fully trust each other to maintain a set of global states. The parties agree on the existence, values and histories of the states. As the technology landscape is expanding rapidly, it is both important and challenging to have a firm grasp of what the core technologies have to offer, especially with respect to their data processing capabilities. In this paper, we first survey the state of the art, focusing on private blockchains (in which parties are authenticated). We analyze both in-production and research systems in four dimensions: distributed ledger, cryptography, consensus protocol and smart contract. We then present BLOCKBENCH, a benchmarking framework for understanding performance of private blockchains against data processing workloads. We conduct a comprehensive evaluation of three major blockchain systems based on BLOCKBENCH, namely Ethereum, Parity and Hyperledger Fabric. The results demonstrate several trade-offs in the design space, as well as big performance gaps between blockchain and database systems. Drawing from design principles of database systems, we discuss several research directions for bringing blockchain performance closer to the realm of databases.